I made a query on this forum or another (I can't remember which) last year regarding engine oils. I was told that regular automotive oils are not formulated to operate in an engine/transmission/clutch environment and will break down faster as well as not properly lubricate the clutch. That is why we use oils formulated specifically for motorcycles.***Was that the correct answer?***
mjpliv, you ask-- "Was that the correct answer?"..No real straight forward answer.. There is some truth to what you read but the modern day auto/truck motor oil is way superior to what was available or speced out in years past so any of the new oil's are way better than what was needed on the older Wings.. The modern motorcycle engines are tested & speced out for the modern emission compliant oils so nothing lost there either..
What you read mostly applies to Harleys & other air cooled as those are air cooled & do run much hotter than the water cooled Wings.
As long as the oil you are using meets the OE spec you won't have any oil related problems.. Probably the biggest change in modern oil thinking is the use (well actually (non-use) of a 10-40 oil.. The higher the spread between the low & high number usually the less actual oil is in the mix & the more fillers & modifiers used.. Those fillers & non oil additives are prone to shearing as they go through gears & chains so the oil breaks down it’s viscosity much faster.. Most new cars & trucks warn specifically against using a 10W40 oil & opt for a 10-30 or some other low viscosity spread oil.
An added problem with the newer car & LIGHT truck oil’s is that they have some of the anti-friction additives either removed, lowered in quantity, or changed to less effective additives to keep from polluting the catalytic converter..
SO, where does leave us?1)- Just use the modern car/light truck oil & change often (nothing wrong with that).. ANY of the modern emission compliant oils will work well as long as they meet the OE spec & are changed often..
2)-Use a modern diesel speced oil like 15w40 or 15W50 (usually a 15W oil is a diesel speced oil.. The oil’s rated for HD or diesel use still have a much better anti wear package due the higher bearing & cam loads on the diesel engines & don’t have conventional catalytic converter to worry about. In fact Harley recommends a diesel rated oil for replacement..
3)- Use a motorcycle or air cooled rated oil as those have a littlie higher resistance to high operating temperatures & better acid handling additives in them ( on all the tests I have seen, the motorcycle only oils aren’t that much better to justify the additional cost & in some cases aren’t even as good in certain cases. Just because the MoCo or oil company recommends it doesn’t always mean it is better, it just means the MoCo (or oil company) will make money on it & it will meet the minimum requirements of the engine design…
4)-Use a quality synthetic oil, preferably a long drain type (like Mobil 1).. Those synthetics use a much more precise base stock so have less polymers & viscosity improvers in them so are a lot better at shear resistance,, handle high operating temps better,, (usually) have superior additive packages in them, & do flow better at low ambient starting temperatures… The only down side I can see to using full synthetics in a wet clutch motorcycle engine is the possibility of the clutch slipping in extreme use conditions.. So far the feed back on this & other M/C sites seems to indicate this isn’t a big issue (at least for normal light duty usage)..