Originally Posted By: carock
... what oils should I be looking at using in my new air cooled Royal Enfield that shares engine and tranny oil? The book calls for 15w50 ester based semi synthetic. I have 2000 miles on BMW 15w50 semisyn (3 changes in that time), and 1000 miles on Motul 300v synthetic. What oils should I think about using for the long term? I am a little curious why the book calls for an ester based semi synthetic instead of a full synthetic. It would seem to me that a full synthetic would have to be better.
1. Use what the book calls for, however boring that seems to be, yes, we all get caught up in it.
2. The reason the book calls for a semi syn is the same. The motor company knows there are some elements of conventional oil that have lubricating benefits for the engine.
These elements get destroyed when oil is super refined into synthetic and also missing from true ester synthetic.
3. Many people think synthetic is the end all of all good oil and superior to any conventional. That is not entirely true, it really depends on the application and intended purpose.
Oil companies of course market to the public since the public thinks that way and they make massive amounts of profits on it.
There is a reason, Harley, Indian, Victory, Yamaha, Enfield, etc, etc, etc are semi synthetics in their OEM oils. Lets not forget even Marine Engine Companies as well.
Im not saying good or bad, not what this post is about, but just calling an oil "Full Synthetic" does not make it superior to Conventional, It depends on what you are trying to achieve, balancing change intervals with wear and of course the design of the engine as well as the operating conditions and materials used.
With all that said, like anything, you can pretty much use what you want it jsut if you want to trust the maker of the product over your own feelings.