Being here in Tucson AZ where the temps do swing greatly, 110 this summer and "winters" that get lows below freezing (like tonight) I run Redline or Royal Purple 20w50 spring through fall and a 5w30 in the winter. Suprisingly, this was recommended to me by a stealership.
5W-30 GOOD, 10W-40 BAD? Both are Rated SM?
OK, I have been trying to follow the various oil controversies: the latest is that 10-40 is BAD and new car makers are warning not to use it (we should use 10W-30).... the reason?
10W-40 has more polymer viscosity enhancers to make the oil shift 30 points from 10W (cold) to 40W (hot), compared to 10W-30 that only shifts 20 points. The oil is the lubricant (not the viscosity enhancers) so you want the one with less of the viscosity enhancers...
BUT:
My Chevy Cavalier says to use 5W-30, which is "25 point shift". Is there really a significant difference in the volume of oil in comparing 10W-30 and 10W-40 or 5W-30?
My owners manual recommeds the 5W-30 because it's operating range allows outside temps down to about -20F. 10W-30 or 10W-40 goes down to about 0 degrees F. Not that I care living in california.
Anyway: what % of the volume of a quart of "oil" is made up of the viscosity polymers?
AND:
Why is it every quart of oil I have in my garage which are: full synth (10W-30), synth blend (10W-30), Castrol/valvoline conventional oil 10W-40, all have the same API service rating of "SM" which I believe is their highest rating?
Are new car makers actually saying that oils rated at the highest service rating are not good enough?
10W-40 has more polymer viscosity enhancers to make the oil shift 30 points from 10W (cold) to 40W (hot), compared to 10W-30 that only shifts 20 points. The oil is the lubricant (not the viscosity enhancers) so you want the one with less of the viscosity enhancers...
BUT:
My Chevy Cavalier says to use 5W-30, which is "25 point shift". Is there really a significant difference in the volume of oil in comparing 10W-30 and 10W-40 or 5W-30?
My owners manual recommeds the 5W-30 because it's operating range allows outside temps down to about -20F. 10W-30 or 10W-40 goes down to about 0 degrees F. Not that I care living in california.
Anyway: what % of the volume of a quart of "oil" is made up of the viscosity polymers?
AND:
Why is it every quart of oil I have in my garage which are: full synth (10W-30), synth blend (10W-30), Castrol/valvoline conventional oil 10W-40, all have the same API service rating of "SM" which I believe is their highest rating?
Are new car makers actually saying that oils rated at the highest service rating are not good enough?
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