Join Date: Mar 2010
Location: Columbus, WI
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EDIT - I WAS WRITING THIS POST THE SAME TIME AS "TPyle"
you are what seems to be putting wayyy to much thought into this. we run 15w40 in equipment all year round and in the winter it can be as cold as like -10 here unless something extreme comes along. i run 5w40 schaffers in my cummins. necessary? probly not. most 5w40's you'll find are a full synthetic, which is supposed to offer easier starting in cold weather, extended oil changes, quicker warm up times. Basically better for cold. now if you look in your book 15w40 might be in the charts to run down to 10 degrees idk idc. depends where you live. but ive always been told once you go to synthetic you really shouldn't switch back and forth. SYNTHETICS are rated for a wider range of temp too!
this kinda got long on me but really it just comes down to your climate? if you live somewhere dont get really hot or really cold dont waist your time with 5w40, but say you live in Alaska then i would without a doubt run it.
Current- 2016 3500 CC SB 6.7 AISIN MAX STEEL LARAMIE
2010 3500 Crew LB Laramie, G56
Last edited by farmin; 12-12-2010 at 11:17 PM.