M1 5W-30 or 10W30 for warm weather only vehicle?

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Apr 27, 2009
Since I am not an expert in oil I was curious if there would be any benifit to running a 10W-30 oil vs. 5W-30 for a vehicle that is only driven in the spring and summer where the temperature is above 40F.

The vehicle asks for a 5W-30 but 10W-30 is listed ok in the owners manual. This is for the 5.7 LS1 engine (04 GTO).

Would I gain any benifit or would I actually be better sticking with a 5W-30 or 0W-30. I am currently using the 5W-30. I am more concerned with HP and/or wear protection gain/lose between grades.

The oil would be M1. $22 @ WM
I only suggested the 10w because it may be a bit less volatile. Otherwise, it really does not matter.
It's my understanding that the LS1 community loves German Castrol 0w30. IIRC, the 5.7 is the same engine in the Vette. Patman really liked GC. My nephew has a goat, he runs GC. Are you subscribed over at http://www.ls2.com ? Seems like a lot of GTO owners post there... For your question, I think either is fine, but I always lean toward the smallest spread between numbers myself, so I would go for the 10-30. I see this is your first post....Welcome
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Originally Posted By: Eddie
Go with the factory recomendation. Even 100 F. is considered a cold engine when normal operating temp is 190-210F
M1 10-30 will work great in summer or winter. I use it in my Merc here in Illinois and have no problems even when it's -10F.
I live just across the river from you, 20 miles from the arch.
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