Engine oil

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Jun 3, 2005
Had my Commando engine rebuilt last year and did about 1600 miles over the summer.was told just to run the bike on Duckhams 20w-50 classic mineral and this would be more than good enough.Before the rebuild the previous owner ran the bike on silkoline semi synthetic 20-50, he said that the bike would be best left on this oil, Do i keep the Duckams or change back to Silkoline for the summer 2007 as most people seem to have different opinions when it comes to oil choice and there seems to be more protection with the synthetic or semi synthetic type.

I've been running mine on millers 10/60 fully synthetic, flows easily as startup and does not thin much at all if any at full temp.
I would try Silkolene Chatsworth 40,I use this all year round in both my Commando engines & other half uses it in her Triumph twin with no problems.
Use full synthetic in your bike. The film strength alone,of synthetics, make them worthwhile,especially for a machine that may not get ridden daily,or even weekly. Let the dead dinosours rest in peace. :D

Hi Bruce,

What kind of full synthetic do you think is best?


Which proves the point that you ask 10 different people about oil & get 10 different answers. I used good quality straight 40 latterly Rotella high detergent oil as you could buy 25 litres at half the price of "classic" oils in fancy tins. I did this as the rebuild speciallists such as Norvil & SRM stater that guarantees are void if anything other than monogrades are used. However recently I have changed to Miller V twin 20/50 which is designed for air cooled twins such as Harleys BMWs etc. It should be high quality & stand temperatures of commandos. I change at less than 2000 miles anyway. Big benefit is ease of kicking over from cold & nice quick warm up. An old ex mechanic told me that in the 1970s wear on the valve stem by the rocker never used to happen, & he put htis down to better oiling by multigrades from cold. Jury is out on this one & nnobody comes up with defineite answer. Frequent changes vital though, plus proper oil filter.
Like Geoff says, everyone has their opinions on oil and reasons for using. The UK experts like Norvil and Norman White urge straight 40 and 50 and I'm sure no major damage will occur with good quality monos. It's just nice to see the difference synthetics make to reduced bore and ring wear as examples. Insignificant steel and iron particles on the magnetic plug at 1500-2000 mile oil changes is probably a good indicator. I use Amsoil 20/50 which comes out near the top for lower wear and resistance to breakdown at high temp. In the US Redline 20/50 is another quality oil. Mobil 1 V-twin 20/50 for HD's also good though not avaialble here.
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