New user here. I read the motor oil university on this website but I need some help with something and I'd appreciate some insight.
Something I've always wondered was why do manufacturers recommend different high temp (say 5w30 or 5w40) weights for their vehicles. If I understand correctly, the viscosity grade should be based on bearing clearance for a particular engine. If the operating temperature is constant, this should logically just be a single grade at operating temp, with winter grade varying for different temperature ranges, correct?
For instance, here is a chart from a 2006 f250 6.0l powerstroke diesel I have:
How come 30 grade and 40 grade are recommended for different temp ranges when the operating temp should be the same regardless of the climate?
Also, because motor oil is never thinner than operating temp at cold start, is there a reason why you *wouldn't* want to go with a 0 winter grade (like 0w40) even if the manufacturer specifies a 15w40, no matter what climate? Is there something about the spread between the numbers that make a 0w40 oil less stable than a 15w40? or will it break down faster and not guarantee a 40 weight?
Sorry if my terms are all wrong, new to this but I couldn't find answers to the questions above.
Something I've always wondered was why do manufacturers recommend different high temp (say 5w30 or 5w40) weights for their vehicles. If I understand correctly, the viscosity grade should be based on bearing clearance for a particular engine. If the operating temperature is constant, this should logically just be a single grade at operating temp, with winter grade varying for different temperature ranges, correct?
For instance, here is a chart from a 2006 f250 6.0l powerstroke diesel I have:
How come 30 grade and 40 grade are recommended for different temp ranges when the operating temp should be the same regardless of the climate?
Also, because motor oil is never thinner than operating temp at cold start, is there a reason why you *wouldn't* want to go with a 0 winter grade (like 0w40) even if the manufacturer specifies a 15w40, no matter what climate? Is there something about the spread between the numbers that make a 0w40 oil less stable than a 15w40? or will it break down faster and not guarantee a 40 weight?
Sorry if my terms are all wrong, new to this but I couldn't find answers to the questions above.
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