15w40 for 99 vortec 350 4x4?

[BillyTheKid]

15w40 will work fine, I have done it quite a few times and my 98 still runs fine 185k and counting.

 

[doyall]

Originally Posted by DoubleWasp
... In marine service, millions of them are fed nothing but 25w40 and 15w40. The engine doesn't care. ....


Volvo-Penta specs xW-50 for my marinized GM Vortex 5.0L if their "special" SAE 30 Synthetic is not available. I have many, many hours on 0W/5W/15W/20W-50's with no oil-related issues. It actually has 5W-40 in it for this season.

 

[DoubleWasp]

Indeed. Volvo did have a lot of issues with the SAE30 and valvetrain wear. Most engines have a bulletin superceding a 40 weight diesel oil and knocking down the SAE30 as recommended oil.

Now that they're all emissions catalyzed engines, 5w50 SN oils are the go-to oils to prevent catalyst contamination. Mobil 15w-50 as well, with a Stern warning not to use Mobil motorcycle version. I'm assuming because of phos and zinc levels.

Marine Power has this specific recommendation for their GM based marine engines.

 

[addyguy]

IMO good choice for that engine.

 

[wtd]

I run 5W-30 Castrol HM in my 98 with the 5.7L vortec but it only has 137,000 miles on it.

I do run 10W-40 Castrol HM in my 98 with the 7.4L vortec and it runs fine on it but doesn't start as well in the colder months as it did on 5W-30. This truck has 117,000 miles on it.

I will tell you that when my 98 with the 5.7L was fairly new, I tried Mobil 1 in both 5W-30 and 10W-30 and my engine did not like that oil at all. The engine became noisier and I had increased oil consumption. I finally went back to a conventional oil and both of those things went away.

 

[westcoaster]

I also have a 99 Suburban with 285 Kilometers. Runs excellent. Just fixed a couple of oil leaks. I live in the interior of BC so my temps in the summer average 37 degrees. I also tow my trailer with it and with the high temps, I also run the Rotella 5W-40. No issues. Purrs and runs smooth. The 15W-40 is a touch thicker but will serve you nicely. Might pay about 1/2 MPG but that's minor. I just did an oil change with a franken-brew of Rotella 5w-40 and Mobil High Mileage 5W-30 and topped up the jug with a touch of Pennzoil Platinum 5W-30 just for sweetness!!!!!! I love oil mixology!!!!