What I want to know is at what point does oil become either car oil or bike oil? does it come from different oil wells, don't think so, does it go to different refineries, doubt it, does it have different additives, yes it can have a milage enhancer like PTFE and this could make your clutch slip, does it undergo different testing, yes the grading is different (the letters and numbers) for car and bike oils but it doesn't mean the oil is different.
What we need is the person who puts the labels on the cans of oil to tells us the facts. I know bike engines tend to rev higher than cars do but which has to do the most work, a 1000cc bike at 200Kg plus max of 2 people or a 1400cc car around 1000Kg plus up to 5 (or more) people?
Oh and I use GTX 10/40w semi in my FZ6 which is around £23 but the last lot I bought at £10 for 4 litres at wilco's in a sale and also got some 15/40w for my other bike at half price in 1 litre packs as it takes 5 litres.
you can get 20L drums with proper semi synth Silkolene Super 4 10W-40 for about £90, so paying £23 for 4L car oil is no saving at all? 4L Silkolene proper motorcycle oil cost the same:
http://www.opieoils.co.uk/p-846-silkolene-super-4-10w-40-semi-synthetic-4-stroke-motorbike-oil.aspx
This article explains the differences with exact details about the exact oil content in car and motorcycle oils:http://www.sportrider.com/oils-well-ends-well-part-2Long story short some car oils may be better than some motorcycle oils and vice versa. Good oils have the same ingredients. The only problem in some good car oils is the additives that make possible oil changes for say 10 000 miles - these are not good in motorcycle and may foc up your clutch.
Think everyone agrees bikes are harder on oil than cars and yet they design bike engines so that one oil has to do all the jobs. Seems mad. I wonder why they don't separate the component parts of a bike engine like gearbox, clutch, cylinder and then have an oil for each section? An engine would have to last longer. Maybe that's why they don't do it
If you look at the article above about the content of different components in oil - there is no difference between some good car oils and good motorcycle oils. Means you can use any if it is good. Emphasis is on good
INB4 good car oils are also expensive even more expensive than good motorcycle oil.
The whole debate point is wrong. There are no excellent car oils that are cheaper than motorcycle oils. There are good oils priced accordingly
The price difference between crappy oil and good oil is about £10 for one oil change. The awfull cranking sound of your engine running on crappy oil - priceless.