Different Viscosities During Different Seasons

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Apr 3, 2006
Morrow, Georgia
Can someone explain a real reason to use thicker oils in hotter climates if the manufacturer makes no mention of it? From all the information I have read on BITOG, it seems that thicker oils actually cause more drag and therefore cause engines to run hotter, so why would a thicker oil, that would cause an engine to run hotter, be necessary in a hotter climate? I run 0/5w-30 Amsoil all year round and have no problems at all.
Maybe you're looking at it from the wrong end (not really - but it wouldn't be so odd if you did). Suppose they're using the correct weight in the warm weather and are just compensating for the severe shift in "starting temp" in an attempt to offset the parasitic losses [I dont know]
Maybe I should have added in some more wording. If the manufacturer recommends one weight for all temps, as with mine a 5w-30 is recommended above 0 F (basically all year round in my area). However there are some people who would run a 5w-30 in the winter and then a 10w-40 or 20w-50 in the summer. I just don't see how, or why, that is necessary if the engine is spec'd for a 5/10w-30.
I think most premature engine deaths today occur from neglect and owner modifications, not the incorrect viscosity or brand of oil. I'm also guessing most sludge prone engines would be fine on 3000 mile OCI with the cheapest of 5w30 dinos. Most sludged engines i've read about seem to be a result of extended OCI's. I live in Texas and the mazda dealer here uses motorcraft 5w20 and 5w30 in everything they service year-round and there does not seem to be any rash of engine failures because of it. Older engines may indeed benefit from heavier viscosities in the summer due to severe wear, leaking seals, etc. but in newer and healthy engines, 5w30's seem to be excellent.
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