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Old 03-02-2013, 03:44 PM   #18 (permalink)
BHarvey
Master EcoModder
 
Join Date: Nov 2010
Location: Atlanta
Posts: 403

Sweetie - '11 Hyundai Sonata GLS
90 day: 39.35 mpg (US)

My Miles - '03 Combo GLS/KLX/Ninja
90 day: 40.49 mpg (US)

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Quote:
Originally Posted by Varn View Post
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.

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.
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