2020 GMC 2500 - Is 10-30 OK?

can I use 10-30 oil in my 6.2 liter diesel engine? I have always used straight 30 wt. but am finding it harder to obtain.

What does GMC say should be in this engine? I am willing to bet GMC never specified straight 30 wt oil for this engine. My research say it should run 15W40 diesel spec oil

I guess you would lose that bet. They say sae 30 sf/cc or sf/cd.

I should have added that this is a 1982 GMC.

Then, why are you trying to second-guess the people who designed and manufactured your engine in 1982?

I would think that the oil performance has improved in 27 years and remember the Car Talk guys mentioned something about that.

Yes, you should have added that if you want accurate answers. Your post says 2020 GMC.


Sorry to upset you about this. Didn’t seem like that big of a deal. I didn’t list my vehicle as 2020.

The tile shows up as 2020 GMC 2500.

“2020 GMC 2500 - Is 10-30 OK?”

I just quoted the title of the post

So . . . yes, you did list your vehicle as a model year 2020 GMC

O.K. Let’s start over. My truck is a 1982 GMC Sierra C2500 3/4 ton pickup with a 6.2 Diesel engine. Does anyone know of 10/30 diesel rated oil is appropriate?

Should be fine, considering the only difference from the 30 weight that’s recommended is the 10w30 flows better when cold. 15w40 would be my choice if you’re in a warm climate.

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Frankly if it was my 1982 diesel I would just use a brand name oils for diesels and be done with it . I might call a dealer parts department , contact Rotella or go by a diesel truck repair place.

I would buy 15w40, when it’s on sale next time at Costco


Thanks John. I live in Northern California so temp shouldn’t be an issue.

I don’t have information for 1982 but for the 1985 6.2 L diesel engine 10W30 is the only oil listed.

I would use modern 15W40 oil made for diesel engines, the common 10W30 found today oil will not have the amount of zinc necessary for flat tappet engines unless it is diesel specific motor oil.

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No need to apologize to me. You were looking for advice and didn’t supply the information so you got the best info I could give based on that.

My advice stands, 15W40 diesel spec oil.


I see Rotella and Delo on Amazon for what I think is a reasonable price. I also see that our local tractor and farm supply store carries Rotella, so check one of those stores if you have one nearby and if you didn’t think of that already.