Oil

[akarpf]

I need to find out whats the best oil to use in my 84 6.2liter ( c )? I was thinking Shell Rotella 10W-40 Oil but i'm not sure if thats ok to use. And I live in North Louisiana. Where the coldest temp gets in the 30's maybe for one or two days ( we may see 20's in a blue moon ) and the hottest is around 110+ ( aka HELL ).

[DmaxMaverick]

DO NOT use 10w-40. The Rotella you are looking at is likely 15w-40, and rated for late model Diesel use. A recent standard, is 15w-40, API CI-4+, for example. You can use any 15w-40 with an API rating of CG-4 or later (the "G" part is the package index, and is the progressive rating indicator, higher letters are later formulations). Many "S" rated oils (S = Spark ignition, C = Compression ignition) also carry a C rating, but most often is not adequate for automotive (1978+) Diesel engines. A CF rated oil may be fine in an old tractor, but not good in automotive Diesels.

For colder climates, other viscosities are available, in dino or synthetic, but the requirement is the same for the API rating. For the South, any 15w-40 with the correct API rating is recommended. Shell Rotella 15w-40 is very popular with commercial fleets.

[WyoDutch]

Back in the summer of 1984, I bought my GMC High Sierra diesel 4by4.

The owners manual specified a CF/CD 15-40 oil. Pennzoil was one of the few companies marketing such an oil back then. I used Pennzoil in my 3,000 mile oil changes for the next 20 years.

Five years ago, I had a glow plug explode in one of the cylinders and wound-up doing a rebuild. After the rebuild, I put 10K miles on it and installed an Amzoil dual filtration system and switched to Red Line synthetic diesel motor oil.

Now... I change the filters and the oil once a year.

I've come to the conclusion that it isn't the oil you use.. but rather.. how you use it. My old pickup never goes into gear... winter or summer until the cold start circuit switches off... letting me know the engine is warm enough to go. I use quality (air, oil, fuel) filters and change them regularly.

I look under the hood of my 84 and the compare it to what I see when I view the engine well of my 2009 Duramax. My old 1984 is simple and clean, while the 2009 DMax looks like a plumbers nightmare. 25 years of government regulations makes the difference.

[rustyk]

DO NOT use 10w-40. The Rotella you are looking at is likely 15w-40, and rated for late model Diesel use. A recent standard, is 15w-40, API CI-4+, for example. You can use any 15w-40 with an API rating of CG-4 or later (the "G" part is the package index, and is the progressive rating indicator, higher letters are later formulations). Many "S" rated oils (S = Spark ignition, C = Compression ignition) also carry a C rating, but most often is not adequate for automotive (1978+) Diesel engines. A CF rated oil may be fine in an old tractor, but not good in automotive Diesels.

I'm a former field engineer for Shell. Rotella (for NA engines) is slightly different in formulation from Rotella T (for turbocharged engines). Actually, the rule-of-thumb recommendation for engines of the OP's era is a straight-grade (i.e. SAE 30) unless cold-weather starting issues appear. However, "straight" Rotella is hard to find, and Rotella T 15W-40 is fine to use...but let's keep the record straight. :) BTW, "S" is for "Service" and "C" is "Commercial" under the API (American Petroleum Institute) - but I like your definitions, although wrong, better!