Quote:
Originally Posted by Varn
I buy into the cold weather viscosity as being a drag but once the engine gets up to temperature having too thin of oil may increase metal to metal contact.
I normally run 15w-40 in the summer and 5w-40 in the winter. The 15w40 is cheaper. I have tried thinner oils in my fords and never noticed any change in economy. I would rather have the increased protection of the 40 weight equivalent.
All of my driving is at least 6 miles with at least one long trip on a tank.
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BUT, thicker oil runs hotter than thin oil, which means you loose most of the supposed 'protection' benefit a thicker oil might give because it runs hotter, which means thinner.
A 40 is thicker than a 20 at all similar temps, but if 20 runs cooler by about 25-30f, then the viscosity and protection will be very much the same.