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What motor oil is best for my aircooled Porsche?
(or any high performance engine)
by Charles Navarro
Last Updated 01/18/2012
The purpose of proper lubrication is to provide a physical barrier (oil film) that separates moving parts reducing wear and friction, but there are many surfaces within an engine that operate with metal-to-metal contact, again popular belief, that are very highly dependant on a strong and robust anti-wear film. The top piston ring operating in sliding contact with the bore operates in a mixed lubrication regime consisting of both boundary (metal-to-metal direct contact) as well as hydrodynamic (oil film between moving surfaces) lubrication. The majority of non-corrosive wear occurs where boundary lubrication exists, especially at cam lobes, tappets, cam follower/buckets, and rockers. Oils contain dispersants, friction modifiers, viscosity modifiers, anti-foam, anti-corrosion, antioxidant and anti-wear additives, all of which can affect the strength and durability of anti-wear films. The focus of this study is on the levels of zinc and phosphorus found in motor oils and their interactions with other additives, more exactly, the zinc (Zn) and phosphorus (P) that makes up the anti-wear additive ZDDP, zinc dialkyl dithiosphosphate, as the ZDDP level is causing concern for all older engines, including aircooled Porsches, with modern oils.
What general characteristics make motor oils specifically well suited to an aircooled or other high performance engine? Aside from recommendations issued by Porsche, what makes a good oil? These oils must be thermally stable, having a very high flashpoint, low noack volatility, and must “maintain proper lubrication and protect vital engine components under the extreme pressure and the high temperature conditions” found in aircooled Porsches. Many well-known Porsche engine builders recommend 15w40 viscosities below 90F ambient air temperatures with 20w50 for hotter climates above 90F average ambient temperatures in street use. Porsche recommends and uses Mobil 1 0w40 as a factory fill in new vehicles and Mobil 1 15w50 has been a popular choice used by many year-round in aircooled Porsche models. What was once considered a 'safe' oil is no longer as many of these lubricants have been reformulated for many reasons, not limited to allow for protection of emissions controls and for longer drain intervals and shopping by brand alone no longer ensures satisfactory performance.
Even prior to the introduction of the API's SM and now current SN standards, there was concern that current API SL standards from back in 2003 may inhibit the backwards compatibility of motor oils, specifically referring to the limitation of ZDDP, which is "the most effective combined anti-wear and anti-oxidant additives currently available." SAE 2003-01-1957, Effect of Oil Drain Interval on Crankcase Lubricant Quality, Shell Global Solutions. The authors continue to state that oils are required to provide longer protection in severe operation but that an oils performance is "limited by environmental considerations." Furthermore, they state that it is hard to predict the effects of these reformulated oils in just a single oil change and may only be evident over an engine's lifetime. It is hard to know the full extent of the potential damage these new SM oils will have on our performance engines so chose your lubricants carefully.
Porsche’s recommendation in hand, our initial analysis from 2005 and 2006 and from virgin oil analyses going back to the 1990s, we found that then prior SH/SJ formulations of Mobil lubricants tested, including Mobil 1, have had higher Zn and P content than SL, SM, or current SN formulations. Even current "re-introduced" formulations are not the original formulations many shops and owners were used to. Aside from reduced Zn and P levels (now restored in certain products), many products with "adequate" Zn and P still use high levels of Ca detergents, well documented in various SAE publications as known for causing more wear than Ca/Mg or Ca/Mg/Na detergents, as previously used in oils like Mobil 1 15w50, back when it was API SH/SJ rated and prior to reformulation. This confirms the industry wide trend of the reduction of Zn and P from motor oils and switch to Ca-based detergents, with the eventual reduction to 0.06-0.08% or even worse, the elimination of these additives, which are essential to an aircooled Porsche engine's longevity. Depending on how detergent an oil is and which detergents are used, optimal Zn and P levels can range from 1200 to 1500 ppm, lower detergency oils requiring less Zn and P.
Many Porsche repair shops have acknowledged that these newest SN and CJ-4 rated motor oils are not sufficient for protecting any Porsche engine, including newer water-cooled ones. With longevity and the protection of vital engine components in mind, many shops are recommending non-approved motorcycle or racing oils, or the addition of oil supplements at every oil change, for their higher levels of protection. On newer water-cooled Porsche engines where Mobil 1 0w40 is recommended, a simple change to an oil with CJ-4 rating or preferably an oil with SL or CI-4 rating as well as a viscosity of 5w40 rather than 0w40 are two changes that can be done in addition to more frequent oil changes to ensure longevity of newer engines. Granted most of these oils will not come with Porsche approval, so if your vehicle is under warranty, defer to the Porsche approval list and select a 5w40 viscosity where appropriate over that of a 0w40, regardless of API rating, as all will carry the most recent API ratings.
Oil companies have been cutting back on the use of Zn and P as anti-wear additives and switching to alternative zinc-free (ZF) additives and ash-less dispersants in their new low SAPS oils since Zn, P, and sulfated ash have been found to be bad for catalytic converters. One such ZF dispersant/anti-wear additive is boron, which does not foul the catalysts in the particulate emissions filters or catalytic converters. For most owners, the reduction in longevity of a catalytic converter is a small price to pay considering the many thousands of dollars it costs to properly rebuild a Porsche engine. It is worth noting that most Porsches have lived the majority of their lives with high Zn and P oils as found in API SG-SJ oils as late as 2004, and we never hear of problems with their catalytic converters.
In addition to protecting emissions controls, there are many other design considerations in formulating engine lubricants, which include improving fuel economy and longer drain intervals. Many believe that the EPA has banned zinc and phosphorus in motor oils. This is not true. In response to modern engine design and longer emission control warranties which are required by the EPA, manufacturers have turned to reformulation of oils to do this, as well as to improve fuel economy by reducing fiction. High friction can result in areas with boundary lubrication or where high viscous friction forces and drag may occur with hydrodynamic lubrication in bearings. The use of friction modifiers, such as moly (there are many different species of Mo-based friction modifiers, help to reduce friction in metal-to-metal contact with the formation of tribofilms characterized with their glassy, slippery surfaces. Lower viscosity motor oils are key to increasing fuel economy by their reduction in drag where high viscous friction occurs in hydrodynamic lubrication. While lower viscosities improve fuel economy greatly, they also reduce the hydrodynamic film strength and high temperature high shear viscosity of the motor oil, factors both of which are key to protecting high performance engines, especially aircooled ones. It is worth mentioning that lower viscosities will provide better fuel economy, but thicker oils in modern engines greater than what the manufacturer recommends and what the engine is built for will not always result in better protection.
However, it is worth noting that these new API guidelines do not need apply to “racing,” “severe duty,” or any motor oils that do not carry an API “starburst” seal or clearly state for off-road-use only. Motor oils meeting “Energy Conserving I or II” standards should be avoided as well as those with an API SM or ILSAC GF-4 classifications. The European ACEA A3/B3 "mid-SAPS" classifications, which place a cap on P levels at 0.10-0.12% but allow for higher Zn levels, to be better in taking into consideration wear and engine longevity, setting much lower wear limits, while still limiting emissions and protecting emissions control devices. A good example of this is a Porsche approved lubricant - although it may carry an API SM or SN rating, it will by rule require 0.10-0.12% Zn to meet the ACEA requirements. The current ACEA A3/B3 classifications require higher high-temperature high-shear (HTHS) viscosities, stay in grade sheer stability, and tighter limits on evaporative loss (noack volatility), high temperature oxidation, and piston varnish. This makes oils meeting these ACEA standards that much better for your Porsche, especially since wear limits are much more stringent for valve train wear, 1/6th to 1/4th the wear allowed in the sequences for API's SM or CJ-4 standards. Of particular interest is the upcoming ACEA E9 which will incorporate some of the improvements in the CJ-4 standard along with higher Zn and P, making these mid-SAPS oils an excellent choice for older legacy engines.
Failure to use the right oil, use proper filtration, or observe proper changing intervals can affect the performance of even the best motor oil. It is also worth noting that some manufacturers have gone to shorter intervals and requiring fully synthetic oils (Group 4 or 5) due to litigation surrounding sludge formation and failed engines as a result of factory recommended long drain intervals, so drain interval recommendations are often in a state of flux. Based off of extremely long drain intervals recommended by most European manufacturers, some in excess of 30,000 mi at some point in recent history. Most users have found it best to reduce those intervals by half or even a quarter. Porsche over the last decade has had intervals ranging from 12,000 to 24,000 miles and up to 2 years. Based on UOAs provided to us by our customers, new Porsche owners should consider reducing their drain intervals to no more than six months or 5,000 mi. On newer water cooled models prone to IMS failures, some shops even recommend changing your oil every three months or 3,000 mi allowing for early detection of a failing IMS bearing. Also, remember, Porsche drain intervals are based off a fill of min. 10 quarts, so engines with smaller sumps have to run shorter drain intervals! Cars that have less oil volume can benefit from more frequent oil changes.
Vehicles that are driven spirited or on the track, subject to sustained high oil temperatures or RPMs should have their oil changed more frequently or in the case of cars used at the track, the oil should be changed after every event (or every other event). Likewise, vehicles subjected to very short drives or sustained operation in heavy traffic should indeed be serviced more often. Vehicles not driven often but driven hard a few times a year can probably go a year between oil changes as long as the oil is changed before the car is put away for winter for storage. Regular used oil analysis is the best way to determine ideal drain intervals for your driving habits - one good rule of thumb I have seen quoted is to change the oil with the TBN (total base number) is reduced by 50% of the original total (requiring you to also know your oil's virgin TBN). Another common recommendation is to change the oil once it's TAN (total acid number) equals the TBN. Other factors to consider are fuel dilution and shearing out of grade when determining your drain interval. With this knowledge in hand, using a quality motor oil with proper filtration and regular service is the best thing to do for your engine and to protect your investment.
Any information you may receive related to this web site is provided merely as friendly suggestions, not as expert opinion, testimony or advice. Neither LN Engineering nor Charles Navarro endorses or sponsors any information, products or methodologies you may find herein. - Sorry for the legal mumbo-jumbo!
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Frequently Asked Questions about Motor Oils
Do some oils make more horsepower than others?
ZDDP forms AW films only when there is metal to metal contact, so why do I hear that it is so important when there shouldn't be metal to metal contact in the first place?
What oil should I be using to break in a new engine?
Can I use a diesel oil like Rotella to break in my engine?
How should I break in my engine if I don't have access to a dyno to properly break in my rebuilt engine?
Which motor oil do I (Charles Navarro) use?
What viscosity motor oil should I use in my Porsche?
Has Brad Penn, Swepco, or Motul changed their ZDDP levels?
How did you determine the recommended 0.12% Zn and P level (ZDP, a.k.a. ZDDP)?
What motor oils had the 0.12% levels of zinc and phosphorus recommended?
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How can I find what API specification the oil I use meets or how do I find an oil with Zn and P levels higher than an API SL or SM oil?
Is there any potential problems with boosting the Zn and P in my API SM or CJ-4 oil or such a thing as too much ZDDP?
How can I convert between cP and cSt (viscosity units)?
How can I boost the level of Zn and P safely?
Why use a motorcycle oil?
Can I use a diesel motor oil in a car?
What makes Swepco 306 15w40 different from any other diesel oils?
If new oils, with reduced zinc etc., are lacking in lubrication quality, why is it that engines are not being destroyed at a high rate?
My car calls for a 5w20 motor oil. Should I be using a 5w20?
Is there moly in my motor oil? Is moly bad for my engine?
What kind of real-world field-testing have you done?
What oil should I do if I have an older, higher mileage engine? Can I use a synthetic?
Should I use a semi or partial -synthetic or full-synthetic motor oil?
I have been running a non-detergent oil in my engine? Should I switch to a detergent oil? Should I add STP or EOS?
I have been running detergent monograde oils, like Castrol HD30, in my classic car. Can I use a multi-grade?
I have always used synthetic oils. Can I switch to a non-synthetic?
What viscosity motor oil should I use?
Motor oils are superior today than what was available even a decade ago. Why does it matter what oil I use in my aircooled engine since they are "better" than what was offered when my engine was new?
What is sludge?
How can I get rid of sludge in my engine?
I want to learn more about how motor oils are evaluated. How is valve train wear tested for and measured? What other key factors go into evaluating a motor oils performance that pertains to my Porsche?
Who can test my engine oil? (used oil analysis)
What should I be looking for in an oil filter?
What if my engine does not have filtration?
What gear oil is best for my Porsche transaxle (manual gearbox)?
Does it matter what fuel I use?
What fuel system cleaner, lead additive, or octane booster should I use?
I want to learn more about motor oils. Is there any recommended reading?
Frequently Asked Questions about Motor Oils
Do some oils make more horsepower than others?
Aircooled Technology and LN Engineering together just recently completed in January 2008 comparative oil testing of various non-synthetic, semi-synthetic, and full-synthetic oils with some very interesting results, which can be reviewed in our white paper titled "Evaluation of motor oils and their effects on engine output and efficiency."
ZDDP forms AW films only when there is metal to metal contact, so why do I hear that it is so important when there shouldn't be metal to metal contact in the first place?
This isn't 100% true. Yes, there has to be metal to metal contact (friction) to form anti-wear films. What most naysayers don't explain is that there are different kinds of lubrication - boundary and hydrodynamic are just two. Boundary layer lubrication exists where there is always metal to metal contact, like with the top piston ring, cam lobe, tappets, and rockers which makes up most of the non-corrosive wear. Hydrodynamic lubrication exists in areas like bearings, where in the best case scenario, there should never be any metal to bearing contact. The thickness and speed of formation of AW wear films on metal to metal surfaces has to do greatly with ZDDP levels, which detergents are used, and amount of pressure and friction between the surfaces in contact.
What oil should I be using to break in a new engine?
Ideally you want an oil with low or no detergency, no friction modifiers, be non-synthetic, and high levels of Zn and P, to make it as easy as possible for AW wear films to form on engine parts during this critical process.
Brad-Penn offers a SAE 30 break in oil with .14% Zn and P already in the motor oil which requires no additional additives to protect your vital engine parts during the break-in procedure, especially the cam and valve-train. We recommend running a break-in specific oil for the first 100-200 miles, with a change of oil immediately after initial cam break-in, and again at the 100-200 mile mark. If using this oil while breaking in your engine on a dyno, make sure to observe your oil temperatures and try not to exceed 210F to maintain optimal film strength with the viscosity of oil being used.
Alternatively, Joe Gibbs Racing and CMW Oil both offer specialty break-in oils similar to Brad Penn's Racing 1 Break-in oil. In the UK, Millers Oils offers a line of Classic motor oils including "running-in" oil and classic multi-grade oils for older engines needing additional protection. There are countless other oils that should be satisfactory as long as you follow the above criteria for choosing a break-in oil.
Can I use a diesel oil like Rotella to break in my engine?
Many cam manufacturers have recommended Rotella T in the past for cam break in. Remember, this was the CI-4 Rotella T some manufacturers were recommending, not the new CJ-4 Rotella. Be advised that we do not recommend the continued use of the new CJ-4 Rotella T for cam break-in or any other CJ-4 oil for this purpose. Additionally in support of this position, magazines such as Fleet Equipment, in one such article "Focusing on Oil," stated that CJ-4 oils should only be used in 2007 and later diesel engines and that earlier diesel or mixed fleet engines should remain on CI-4 oils.
How should I break in my engine if I don't have access to a dyno to properly break in my rebuilt engine?
Although not directly related to oils, I get asked this question very often. If you have questions on how you should break in an engine and proper break in procedure, we recommend reading the following articles about the subject:
http://www.mototuneusa.com/break_in_secrets.htm
http://www.aircooled.net/gnrlsite/resou ... gnbrkn.htm
Which motor oil do I (Charles Navarro) use?
Although there are many excellent motor oils out there, considering the wide array of oils I have access to, I currently am using Brad Penn 20w50 API SJ for the summer and winter months in my aircooled Porsche since it never sees sub-freezing starts. The Brad Penn Penn Grade 1 Racing oil is the same "green" oil everyone was familiar with back when Kendall GT was the best motor oil money can buy, as both the original and this newer product both come from the same facility using genuine Pennsylvania crude. These oils are proven to protect cams, rockers, lifters, and all valve train components as well as provide superior rod bearing life because of their very high HTHS viscosities AND low levels of individual detergents to net a high level of detergency with the use of Ca, Mg, and Na synergistically. Just ask anyone about the "green" Kendall oil from decades past and you'll know why we like it so much. Likewise for winter service, we run Brad Penn a 50/50 blend of Brad Penn 0w30 and 20w40, which yields 10w40 API SJ with slightly higher synthetic % than the off the shelf 10w40 product by Brad Penn.
Another great oil, if not a bit expensive for a non-synthetic oil is Swepco 306 15w40, which comes highly recommended by Jerry Woods, a very well-respected and experienced Porsche engine builder, and is another oil we regularly use. This is what I use in my 6.0 Powerstroke diesel (including their 10w30 for winter use).
Both the Brad Penn and Swepco oils are highly refined paraffin base stocks, and I feel they are excellent choices for aircooled engines, providing better protection and used oil analysis wear results than most fully synthetic oils.
In our track Porsches (1999 Boxster and 2010 Cayman S) we use primarily Motul 8100 X-Cess 5w40. Both used oil analysis and physical engine teardowns have proven this lubricant to be a superior choice to Mobil 1. Outside of warranty, Motul 300V is an excellent choice as welll. Likewise, Joe Gibbs Racing 5w40 is our preferred non Porsche-approved lubricant which was co-developed by Flat 6 Innovations for superior performance in M96 and later water-cooled Porsche engines.
Very important in my consideration of any of these oils are that they have the proper balance of Zn and P as well as level of detergency. Oils with high detergency need equally high levels of anti-wear additives as well as those oils using Ca-based detergents also need more Zn and P that those oils that use Mg and/or Na detergents. Brad Pen and Motul all use lower levels of Ca detergents and the less aggressive (lower wear) Mg and Na-based detergents. Swepco uses solely Ca based detergents, as do all diesel oils.
I do not recommend using ZDDP boosters of any kind unless it is your last resort!
What viscosity motor oil should I use in my Porsche?
Porsche nicely answered this one for us (from '84 911 owners manual). You can use a 20w50 year round, even with cold starts to 20F, which covers the majority of Porsche owners. I might add, if your Porsche is also your daily driver and you see repeated sub freezing (32F) starts, it wouldn't hurt to use a 15w40 instead. The other recommendation frequently given by engine builders is that a 15w40 can be run up to 90F ambient air temperature and at higher temperatures, a 20w50 should be used.
We have also tested the Brad Penn 20w50 versus a 50/50 blend of the Brad Penn 0w30 and 20w50, which yields a 10w40 viscosity, with near identical low wear levels, regardless of viscosity. The used oil analysis for the 10w40 can be viewed in PDF here as well as for the 20w50 by clicking here. Both sets of tests were conducted on a 1991 c4 cab with a 3.6 liter normally aspirated 964 engine with approximately 60,000 original miles.
Although the chart shows fuel-efficient oils, modern fuel efficient oils should not be used in your aircooled or watercooled Porsche.
Has Brad Penn, Swepco, or Motul changed their ZDDP levels?
No. We get this asked of us all the time. All these recommended oils have more than enough Zn and P and have not changed in years. Continuted teardowns and used oil analysis by our customers ensures these oils are still performing as well as they have previously regardless of API rating mentioned on the label.
How did you determine the recommended 0.12% Zn and P level (ZDP, a.k.a. ZDDP)?
There are many excellent SAE technical papers on the subject, but the one I found most interested was from 1977 titled "Cam and Lifter Wear as Affected by Engine Oil ZDP Concentration and Type." There is some background that is needed to shed light on their results. First of all, there are different types of ZDPs. There is an Aryl ZDP which is the most stable form. There is also an Alkyl ZDP which although is not as stable, exhibits the best wear protection.
In various fleet tests, it was determined that the best performance was from oils containting all Alkyl ZDPs or predominantly Alkyl ZDP blends. They also looked at the performance of "ashless" oils (0.03-0.05% Sulfated Ash) vs oils with normal levels (0.11% or higher) and it would appear that oils with lower ash levels needed more ZDP to provide the same level of protection. I bring this up since the newest CJ-4 and SM oils require significantly lower ash levels, less than 0.10%. Across the Indianapolis, Phoenix, and Los Angeles taxi fleets observed, oils with 0.11-0.13% Alkyl ZDP resulted in the lowest combined and average cam wear measured. Levels of wear remained low with oils with Alkyl ZDPs as high as 0.19%. Excessive Zn and P levels cam result in additional wear.
The oils that had at least 0.07% Alkyl combined with 0.05% Aryl performed just as well as oils with higher Alkyl only ZDP levels, suggesting some sort of synergistic properties of the decomposition products of the Alkyl/Aryl blend. Combined ZDP levels of the Aryl and Alkyl blend were min. 0.12%.
Our assumption with choosing a minimum Zn and P levels of 0.12% is on the assumption that the best combo of ZDPs are being used for wear performance, not longer drain intervals, with a motor oil that uses low levels of Ca-based detergents supplemented with Na or Mg detergents. Oils for long-drain intervals almost entirely use Ca-based detergents! Oils with Ca-based detergents in high concentrations need significantly more Zn and P, at least 0.145%. Swepco use Ca-based detergents and run additional levels of Zn and P of 0.145% or roughly 1450 ppm, as would be expected from an SL rated diesel oil.
The more detergent an oil is, the more anti-wear additives are needed. That means the correct amount of Zn and P in any given oil is a moving target.
More recently, in the development of the IIIG sequence, developers went so far as to say that there was no need for the VD and VE sequences for testing of OHV (overhead valve) engines because these engines are not commercially available as new anymore and do not reflect the needs of more modern engines. In a SAE paper titled "How Much ZDP is Enough?" from 2004, the resulting trend of decreasing phosphorus is as a direct result of observations that modern engines, with lower spring pressures and lighter vavletrain, including multiple intake and exhaust valves, seems to require only .03% Ph to prevent wear. It was further documented that by increasing to 180 lbs of spring pressure with a .03% ZDP resulted in 267 mil of wear where with .05% ZDP concentration tests resulted in 26 mil of wear. That same .05% oil with just 205 lbs of pressure resulted in 153 mil of wear, requiring .095% ZDP to reduce wear, resulting in just 16 mil.
The ZDP requirements of a motor oil are directly proportional to valvetrain spring pressure. Most older SOHC and pushrod aircooled Porsche engines have significantly more pressure, as a stock street pushrod Porsche 356 or 912 engine exceeds these levels of spring pressure compared to the levels of pressure on modern engines, for which oils are tested for. Newer oils will continue this trend, leaving older engines with fewer and fewer choices for motor oils compliant with the requirements of these older valvetrain, hence our recommendations for using oils with higher levels of ZDDPs as substantiated by earlier testing sequences and the results on engines similar to our older aircooled Porsches.
What motor oils had the 0.12% levels of zinc and phosphorus recommended?
The current API standard is SN and calls for 0.06-0.08% Zn and P, same as with the previous SM standard.
Here are the running averages for all the oils tested thus far, listed by their API rating:
API P (ppm) Zn (ppm) B (ppm) Mo (ppm) Ca (ppm) Mg (ppm) Na (ppm) Total Detergents
SE-SJ 1301 1280 151 357 1936 293 214 2443
CI-4 1150 1374 83 80 2642 199 2840
SL 994 1182 133 273 2347 109 22 2479
CJ-4 819 1014 26 2075 7 2082
SM 770 939 127 122 2135 13 139 2287
I do not recommend the use of any SM or CJ-4 motor oils in any aircooled Porsche, or any vehicle that can benefit from the added anti-wear additives such as pre-ODBII vehicles. If your vehicle is designed to use these newer oils or if your vehicle requires a manufacturer approved oil and is still under warranty, always follow your manufacturer's recommendations!
What oil should I use in my newer Porsche requiring a "Porsche approved" oil, like the M96 or later Porsche engine?
We do not recommend use of most of the Porsche "approved" oils in any aircooled engine, including the 84 and later engines up to and including the 993 that are recommended to run these approved oils.
In the search for a "Porsche approved" oil, a quick glance at various Porsche owners manuals for a Turbo and GT2 as late as 2004 showed a recommendation for an API SH or SJ motor oil, so my recommendation is to find an approved oil with at least an API SL rating - an API SH or SJ would be even better. Additionally, try to use a 5w40 rather than a 0w40, as the viscosity with the narrower spread will have a higher high temperature high shear viscosity and should protect critical engine parts better at the upper limits. You do not need a 0w over a 5w until cold start temperatures are under -25C. Do not run any 0w30, 5w30, or 10w30 oil in your Porsche, aircooled engines included!
Coupled with Google and armed with the "overview of engine oils approved by Porsche "Porsche approval list", including some oils that no longer have Porsche approval but were approved at some point, here are some suggestions for oils. Although previously possible to locate API SJ or SL rated Porsche-approved oils, it's no longer possible to find any as they all carry SM or SN ratings on their labels, but for now, the Porsche approval rating requires a level of Zn between 0.10 and 0.12% while carrying the ACEA approvals, so try to choose a 5w40 viscosity over a 0w40 where appropriate (non-winter use). Outside of the warranty period, non Porsche-approved oils will likely provide better performance with shorter drain intervals.
Shown below are some alternative suggestions for 5w40 viscosity oils that are not necessarily Porsche Approved, but are of excellent quality nonetheless. The higher the HTHS viscosity, the stronger the oil film at high temperatures and the better the protection, in most cases. I have noted some of these oils meet Volkswagen's 505.01 specification for PD TDI engines, which is very rigorous and in my opinion, is a standard requiring additional protection so much so that Mobil formulated a special version of 5w40 in an API SJ that is specific to the 505.01 standard. If cost was no object and I was out of the warranty period, Motul 300V would be my obvious choice. Mobil 1 0w40 and Delvac 1 5w40 shown for reference only. HTHS values per published values by manufacturer. We have selected just a few to show:
Brand
Viscosity
API
HTHS
Porsche Approved
Mobil 1 0w40 SM 3.6 x
Mobil Delvac 1 / Mobil 1 Truck & Diesel 5w40 CJ-4/SM 4.1
Mobil 1 Synt S Special V 505.01 (Europe only) 5w40 SJ 4.67
Mobil 1 (Canada) 5w50 SM 4.3 x
VW 505.01 Castrol 5w40 SL 4.5
Castrol Syntec 5w40 SL ? x
Castrol Syntec 5w50 SM ?
Motul 300V 5w40 SH 4.51
Motul 8100 X-Cess 5w40 SL 3.92 x
Pennzoil Platinum Synthetic European Formula 5w40 SL 3.9 x
Redline 5w40 SL 4.6
Quaker State Q European Formula 5w40 SL 3.9 x
Schaeffer Supreme 9000 5w40 SM 4.57
Although Motul Specific 5w40 API SJ has been discontinued, I have previously run it in my newer VWs with excellent results. It had the highest HTHS viscosity of any oil we ever found, min 4.8 to max 5.1 for a 5w40. Used oil testing showed the best wear results of any oil we have ever run. It was replaced by another Motul Specific VW oil, which now carries a 502.00 approval as well as the 505.01 specification. Interesting point it is the ONLY oil on the market that is a 502.00 oil that meets 505.01 requirements. Currently, we have base-line results for the Motul VW approved 505.01 spec motor oil required by VW. We have been and are always testing many VW and Porsche approved 5w40 oils and several other non-approved ones to see how they perform in street and track use.
Another popular oil highly recommended on the Rennlist forums has been the Mobil 1 Truck and Diesel 5w40 that was an excellent choice up until May 2008, when it was "reformulated" to meet the standards of new diesel engines and hence, is not an API SM/CJ-4 rated oil. Since then, it was reintroduced with an SL rating and higher Zn and P levels, so it again may be a possible alternative choice for those looking for a 5w40 viscosity.
As I have stated previously, I don't have the same faith in backwards compatibility of these reformulated products because there just is not the evidence that they will do the same job over the long haul. To this effect, many fleet service related publications still recommend using SL/CI-4 oils in vehicles without particulate emissions filters, leaving the new reformulated oils only for those engines absolutely requiring these low Zn/P oils.
Of additional interest is a German Porsche AG Technical Bulletin "2000 Motoroelfreigaben", showing 10w40 and thicker oils are also an acceptable viscosity, which was previously considered as being too thick for these newer, non-variocam equipped engines. If that is the case, Mobil 1 High-Mileage 10w40 or even Mobil 1 MX4T 10w40 may be excellent non-approved candidates, the latter motorcycle oil for track use mostly and not recommended for use with catalytic converter equipped vehicles. The only exception to this are the 2001 and later engines with Variocam, since this system is sensitive to oil viscosity and will throw a CEL if the wrong viscosity is used. Another suggestion is to mix 50/50 Mobil 1 0w40 and Mobil 1 MX4T 10w40, to yield a product in the proper viscosity that is recommended with levels of anti-wear additives as originally recommended by Porsche, with an API SH or SJ rating. Also, Mobil now offers a line of racing oils which have very robust formulations, worth considering if price is no object when it comes to oil selection.
How can I find what API specification the oil I use meets or how do I find an oil with Zn and P levels higher than an API SL or SM oil?
Here are some quick links to the API's find brand by viscosity search engine for popular viscosities:
0w40 | 5w40 | 15w40 | 5w50 | 15w50 | 20w50
