NLW73 said:
That's very useful info thanks
So what about the 40 and 50 numbers? Does the 50 provide more protection when the engine is at higher temps and will maintain viscosity and not start to break down like a 40 would ?
50 is just thicker at a hot temp than a 40, I cant remember the temp they test at.
The quality of the oil determines how long it lasts before shearing down and getting thinner.
e.g. a synthetic base oil will resist shearing longer than mineral.
This is why manufacturers like synthetic oils, means the car can go for longer between services.
They also have more additives to keep dirt in suspension longer - bear in mind longer intervals means dirty oil is getting dirtier for longer and the dirt is pumped around your engine.....
Esther base oil is used in race and track applications as its the toughest, resists shearing at sustained higher temps.