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Motor Oil


Well Known and Active Website User
Non-VOC Member
Ok, motor oil back into the Comet this weekend, and hopefully a successful start. Can't get Castrol Classic XXL40 here in the States so have elected to use Castrol 40 HD. I have used 30HD (Heavy Duty) in my vintage VWs since I was old enough to drive. I assume the 40HD will also be suitable for my '70 Bonnie. Anyone care to opine?


Well Known and Active Website User
VOC Member
You could also consider using any modern synthetic or semi synthetic oil intended for modern high speed diesel engines. It will be available as a viscostatic so that you will not get the problems with starting when it is cold (if ever it gets cold where you are) which you might get with a straight 40 grade. It is highly detergent so the engine needs to be very clean inside with all new filters etc. Also, if the engine is to be run in, then stick with the traditional oil for the running in period before changing over to the new product. Good luck.


Well Known and Active Website User
VOC Member
Hello, the Castrol will be fine in the comet, and should be good in the Triumph.
Synthetic oils may be better with the plain bearings, but I prefer straight oil in the Vincent. John.

Prosper Keating

Well Known and Active Website User
Non-VOC Member
I use a quality 20/50 synthetic specifically sold for motorcycle use in my old Triumph and have noticed a general improvement in the way the engine runs. Haven't tried it in a Vincent yet but I don't see why it shouldn't be alright. A couple of Vincent riders here have been using it for three or four years and have noticed improvements as well. It seems particularly good in engines that see a lot of use in urban or semi-urban areas, with more than the usual number of stop-start short journeys. Of course, I have nothing against using traditional mineral oils, although I have rejected monograde oil in favour of multigrade oil (20/50) as the latter is far better than the early multigrades that really did play havoc with old motors. The classic motorcycle press tends in the main to be against any deviation from straight oil orthodoxy but that is because they wish to avoid upsetting advertisers and sponsors who produce and sell "classic oils".


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