Hey guys, what do ya'll think about runnin 15w40 in my engine? I live in San Antonio and the heats been in the 105's + lately so I heard its alright to run from a few guys but I wanted to see what ya'll think. I have access to Mobil Delvac 15w40, so it should be decent stuff if it passes with you guys

 

Its been getting up to 100 here in South carolina. I run 20-50 in my dodge ram,and i still have 5-30 in my blazer. Ive always ran heavier oil in the summer months (except this time in the blazer,oil was given to me). Just remember to change it out once temps start falling again. But then again ha your in texas.

 

Depends. You do realize your oil temp/viscosity reflects coolant temp more than outside ambient, right? Only the first number {15} really applies to ambient.

As long as you do the recommended maintenance, diesel oil is probably better than the highly advertised dino crap, anyway. That long block may outlast your truck even in the no-rust belt.

Actually you should be worrying more about your transmission lubrication/heat than the engine's.

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As for me, I run only Mobil 1... screw the change interval do it when I get around to it.. because almost all my driving is longer trips.

Before you start in on me I have 20 years and over 300,000 miles doing that without so much as startup lifter clack.

 

I don't think that running a 40 weight oil would hurt anything, but it may cause slightly lower mileage given that it is thicker. I would run 10w30 for your climate as the owners manual states.

 

Well, the reason I ask about the engine oil and nothing else is I've aquired three 5-quart bottles of it, so I wanted to make sure it's safe to use first.

 

You gotta watch how you say things.. on the OP I flashed on 'it fell off some truck' and that last didnt help the image.

'a friend gave me.. ' is the protocol.

 

lol well yea-that would be correct as well....a friend gave me some that he had laying around

 

The way I see it, GM spent $$$ in R&D on what kind of oil to use in their engines. The manual states 5W30 in most environmental conditions and 10W30 in higher temps.

I'll go with what the engineers say rather than to take the word of a few buddies who say 15W40 should be okay during the hot summer months.

 

I've been running 20W-50 in my old beaters for decades, seems to work just fine.

edit: Hmm, just looked at the Amsoil sponsor link, and here is what they recommend for my Blazer:

Engine Oil
Grade 1......API*
Maximum Performance Signature Series 100% Synthetic 0W-30 Motor Oil (AZOQT)
Maximum Performance SAE 5W-30 Synthetic Motor Oil (ASLQT)
Performance Plus XL 5W-30 Synthetic Motor Oil (XLFQT)
Performance Synthetic 5W30 OE Motor Oil (OEFQT)
Above 0 F......10W-30

 

I live in Arkansas and most Chevy's around here have whatever you can find laying around the shop in them, lol. But I run 15w 40 Rotella in mine.