I would really like to understand the difference between oil weights, benefits and drawbacks.
I understand the whole viscosity thing, and what the two numbers in the multigrade oils mean, however it seems there are as many men as opinions in this debate. I have heard people say that thinner oil is better as it squeezes into gaps more easily, especially upon start-up, and hence is a better lubricant. I have also heard the reverse. I have heard people switching to lighter weight oil as the car ages, and others the reverse. What is the absolute truth, if there is such a thing?
I remember switching from Mobil 5w-50 to Mobil 0w-40 and immediately noticing the engine seemed to rev more freely and cleanly, whilst at the same time my coolant temp was running slightly warmer. To a rank amateur such as myself, this is a confusing result. One would assume the engine feels more free which would imply LESS friction, but why the HIGHER temp which implies MORE friction?
If anyone could shed some light it would be great. I know there are many articles out there, unfortunately most of them written by hacks who are not mechanics or engineers, and are probably based on nothing more than speculation.
All info welcome, just please no oil wars!
Daniel
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