Full synthetic oil or....

WZ507 · Apr 12, 2014

Matchless said:
If oils for use in modern engines don't contain zinc, how do modern twin cam. motors with bucket & shim type valve actuation manage? There is sliding contact there surely?
Martyn.

I believe at least part of the answer to your question, regarding survival of bucket & shim type valve train, lies in the downsizing of valve train present in the majority of modern engines. Down-sized valve train (often 4 small valves/cylinder vs 2 large valves/cylinder) is light weight valve train (small components, no pushrod, no rocker arm) and light weight valve train employs significantly lower spring force than would a heavier counterpart. In many modern OHC engines the spring force is light enough to actuate a valve by hand force alone (goodbye 100+ lb seat pressure). Another noteworthy point of differentiation between modern bucket & shim vs a pushrod/rocker arm valve actuation mechanism is that unlike the pushrod system, where spring force is multiplied back through a rocker arm to the cam/follower interface, the bucket/shim system sees no enhancement of the spring force at the cam follower interface, thus the forces dealt with are significantly lower.

Considering the entire modern bucket/shim system, i.e., small components, reduced spring force, generous cam lobe/bucket width for large contact area, I think these systems experience dramatically reduced frictional forces at the cam/bucket interface, thus owing to their survival. Such system can likely get by with only a fraction the ZDDP required by the larger more aggressive valve train set-ups.

Speaking from my own experience, I had a 1996 Toyota Avalon DOHC 4-valve V-6 with ~ 200,000 mi on it that had never had the valve cover off. When it developed a valve cover leak and I repaired it I checked the valve lash, and to my amazement was right in the middle of the specification! Similarly I have a 2005 Toyota Sienna with essentially the same engine type that has 250,000 mi on it and the valve cover has never been off. I have no reason to suspect it would be any different than my earlier observation. In both engines I ran dinosaur 5W-30 of every major brand and every off-brand you've ever heard of and changed at 5000 mi intervals. Neither engine used more than 1-2 oz of oil in 5,000 mi. Evidently in this application the valve train was very forgiving with respect to oil composition.

Matchless · Apr 12, 2014

WZ 507,
I think you are probably correct in your assumptions. I have heard that spring seat pressures can be as low as 50lb on a 4 valve motorcycle engine. All that is required with such tiny valves, compared to the dustbin lids older motors use.

Jerry Doe · Apr 12, 2014

+1 for Mobile 1 Vtwin 20/50. My MK3 runs well on it. I used redline 20/50 for the first 500 miles and then switched to the Mobile Vtwin.

Biscuit · Apr 12, 2014

That's a good point about the light valve train a lightish spring pressures. Also, and I don't know this, is it possible those engines have a rounder profile on the cam? That would kind of ease the valve open and let it down gentler too.

Fast Eddie · Apr 12, 2014

WZ507 said:
Matchless said:

If oils for use in modern engines don't contain zinc, how do modern twin cam. motors with bucket & shim type valve actuation manage? There is sliding contact there surely?
Martyn.

Click to expand...

I believe at least part of the answer to your question, regarding survival of bucket & shim type valve train, lies in the downsizing of valve train present in the majority of modern engines. Down-sized valve train (often 4 small valves/cylinder vs 2 large valves/cylinder) is light weight valve train (small components, no pushrod, no rocker arm) and light weight valve train employs significantly lower spring force than would a heavier counterpart. In many modern OHC engines the spring force is light enough to actuate a valve by hand force alone (goodbye 100+ lb seat pressure). Another noteworthy point of differentiation between modern bucket & shim vs a pushrod/rocker arm valve actuation mechanism is that unlike the pushrod system, where spring force is multiplied back through a rocker arm to the cam/follower interface, the bucket/shim system sees no enhancement of the spring force at the cam follower interface, thus the forces dealt with are significantly lower.

Considering the entire modern bucket/shim system, i.e., small components, reduced spring force, generous cam lobe/bucket width for large contact area, I think these systems experience dramatically reduced frictional forces at the cam/bucket interface, thus owing to their survival. Such system can likely get by with only a fraction the ZDDP required by the larger more aggressive valve train set-ups.

Speaking from my own experience, I had a 1996 Toyota Avalon DOHC 4-valve V-6 with ~ 200,000 mi on it that had never had the valve cover off. When it developed a valve cover leak and I repaired it I checked the valve lash, and to my amazement was right in the middle of the specification! Similarly I have a 2005 Toyota Sienna with essentially the same engine type that has 250,000 mi on it and the valve cover has never been off. I have no reason to suspect it would be any different than my earlier observation. In both engines I ran dinosaur 5W-30 of every major brand and every off-brand you've ever heard of and changed at 5000 mi intervals. Neither engine used more than 1-2 oz of oil in 5,000 mi. Evidently in this application the valve train was very forgiving with respect to oil composition.

I think you're right re the lighter spring pressures. Which, IMHO, is a good enough reason to use JS light lifters. One does not have to be in search of higher revs. Conversely, one should be able to use 'normal' revs and enjoy the reduced strain on the valve train, and possible reduced spring pressures (although this would require some experimentation I guess). It also seems logical to me that radiused followers are kinder to the cam, I also think it encourages more oil to be 'squeezed' between the cam and the follower.
You're also right about the bombproof nature of Toyota engines. I've had similar experience and thought at the time that being a Toyota engine repair guy must be a pretty bum job, due to lack of customers!

Fast Eddie · Apr 12, 2014

Madnorton said:
I suppose some just don't get it, Mobil 1 here in the UK = V expensive, Tesco own brand full synthetic = Cheap (even compared to monograde dinosaur oil) it even exceeded the spec of Mobil 1 for a while as the Mobil stuff was having trouble adhereing to the latest EU spec. In my MK3 with magnetic sump plug, the results are encouragingly not visible, so I will use it before anything else. If you ride all year round then use a full synthetic oil, you'll notice one hell of a difference.

Take care there Madnorton, there is a lot more to oil ingredients and additive packages then the spec info shown on the bottles.
Also, the EU specs that you say Mobil couldn't meet we're probably emission specs... which require the removal of the very things that we need in oil (namely Zinc).
The point about modern oils designed for modern cars, is that they are intended for engines that don't need things like Zinc. In fact, they have to remove certain ingredients as they will damage catalytic converters when burned and put out in the emissions.
At the end of the day, for normal use, your bike will probably run for ages on Tesco's finest, so it is perhaps only an academic point, but it is NOT the best oil for an old Norton.

Cheesy · Apr 13, 2014

Biscuit said:
That's a good point about the light valve train a lightish spring pressures. Also, and I don't know this, is it possible those engines have a rounder profile on the cam? That would kind of ease the valve open and let it down gentler too.

Thats kind of the right idea (not rounder but better design), modern engines are a lot closer to the edge but they also know where the edge is (well they should...). There is a lot of work done with load and velocity of the cam-follower interface. Zero velocity is really bad and if the system transitions through this it will fail.

Full synthetic oil or....

WZ507

Matchless

Jerry Doe

Biscuit

Fast Eddie

Fast Eddie

Cheesy

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