If you're one of those who have no idea about oils and how they work, and don't have the time to acquire 35 years of experience looking after vehicles, you might like to raise your awareness a bit by reading the following:
https://motorcycleinfo.calsci.com/Oil.htmlFor those with ... ahem ... shorter attention spans, you might find the opening sections on oil basics a bit too much like an A-level chemistry course. I did but I persevered with it. When you get older you need less sleep. At night, that is. If you are young and have a normal life, skip ahead to the section on 'Choosing an oil for your motorcycle' and read that and the rest of the article.
A selective quote from this section says it all: "Generally, any oil certified for use in a late model Volkswagon or Mercedes turbo diesel is a good choice." The author explains why - in great detail - before making that statement. The curious may choose to backtrack to find out more. The trusting types will not.
Personally, I've run 10w40 fully synthetic diesel automotive oil in my Fazer for 40k miles with no clutch slippage issues, the usual reason for warning bikers away from auto oils. Ah, but what does my motor look like inside? Very clean, far as I can tell from routine maintenance. Still runs like a Swiss watch. But louder. A sizeable number of FZ1 owners in the US run theirs on Rotella-T, the diesel synthetic favoured by the author. Plenty of FZ1s in the 'states have over 100k on the clock. They run like Swiss watches, too. Clever people, the Swiss. But quiet. Except for the cow bells.
Anyway, time was when I would get drawn into extended debate in oil threads but no longer. Let's leave it at this:
It's fair to say that if you don't know what you're buying or understand something about oil other than it's golden and slippery, then sticking to bike-specific oil (preferably fully synthetic) is the safest bet. It will cost you more but the extra few quid are the price of ignorance.
If you take the trouble to learn a bit more by reading, then you can save a few quid and run your bike perfectly well on an appropriate type and grade of fully synthetic automotive diesel oil. I learned this out of necessity. Because bike-specific oils are vastly more expensive than auto oils in Spain, I decided ... well, my wallet did ... that I couldn't afford to remain ignorant (on this, at least) so I researched the subject in depth. As a result, not only am I better off financially, I also have another subject to bore folk with at parties. Win-win.
Best advice I can offer is don't believe everything you read on the internet.
Right, I'm off for a kip ...