by Burgerman » 12 Sep 2017, 22:45
Heres the thing. I know a lot about engines. Having spent years in a previous life studying such things, and running a business tuning and heavily leaning on bike engines. Turbos, nitrous injection, rolling roads and lots of dyno test time and 4 to 5 hundred BHP per litre! I kid you not.
So after all of that I am always baffled by this:
My US left drive Chrysler minivan has a 3000 mile oil change interval recommendation.
The exact same vehicle in the UK but RHD and with UK/EU marketing and handbook says 10,000 miles for some years, and 12,000 for later ones.
So. Which is correct?
I will tell you. The time to change the oil on a petrol engine if you really care, is when it becomes a bit darker but still just about transparent if held up to a light source. Or around 5 years, whichever is sooner since the anti corrosion additives get used up over time just sitting there. Although 50k miles probably wont hurt *that* much if you cant be bothered. Miles don't really matter. Modern oils are fine at silly mileages and will not change grade or properties but they do or can get loaded up with carbon.
Why change if dirty? Because carbon which makes it darker, is abrasive. And in time, the steel crank, soft metal shells, pistons/rings etc use up all the anti corrosion additives and so you get bearing corrosion etc.
The best point to change the oil depends on how much you care. As long as you don't do massive mileages the modern CNC machined engine will outlive the vehicle anyway.
Yes, mobil 1 0w-40 or 0w-50, beats all the others in tests and on friction wear tests, etc. And on 1 litre bike engines at 11k rpm, making 500bhp or so its required. Without it or similar they do around 15 seconds before failing.
But in a street driven low rpm vehicle making 50 to 80bhp per liter, you could use anything! Literally. Corn oil or two stroke oil would be fine. The rest of the vehicle would still die first. All that said, I still use Mobil 1 0w-40. And ignore the 10w-20SAE on the cap/book.