More Oil...

[Richard B.]

I hate to belabor this subject once again, but I have a question on Shell Rotella or similar vs regular automotive oils. I have an 82, and after reading discussions on low usage/mileage, put Rotella in last fall. Annual mileage is 3-4k. Then I heard this may cause problems with the cat converter.

What's the opinion on deisel oils in an 82, and what, if any problems can I expect with the cat converter? And should I really care, since the car will not likely ever see a sniff test in Montana? Can I leave the oil in there till the fall? Continue to use it? Or change it in the morning, and save my dollars for a new cat converter?

Thanks in advance for any advise.

Regards,
Rich #36956

[Duke W.]

Re: More Oil...

Certain motor oil additives have been reduced over the years in spark ignition motor oils because their combustion byproducts are thought to add to normal catalyst aging, which is due to a number of causes.

That said, I would recommend using spark ignition oils in catalyst equipped daily drivers, especially if they must be periodically emission tested. For a vintage car with a catalyst that sees relatively low mileage accumulation and does not have high oil consumption I think the benefits of using CI-4 oils outweigh any possible increased degradation to catalyst performance, since catalysts are a lot cheaper than engine overhauls; and if the catalyst equipped car is old enough or otherwise exempt from emission testing you will never know the effects of catalyst degradation for any cause unless it disintegrates mechanically, which eventually can happen due to the effects of thermal cycling and corrosion.

Duke

[Dick W.]

Re: More Oil...

Rich, I ran an 1989 Chevrolet P/U with a 5.7 V-8 179,000 miles using Rotella 15-40 from the first change until I sold it. Had NO converter problems. Valve seals twice is all the repairs done to the engine.

[Joe L.]

Re: More Oil...

Richard-----

The engine oils primarily formulated for diesel engine service (like Shell Rotella and Chevron Delo) also have an API rating for gasoline engine service. The last time I checked, it was "SL" but I expect that the "SM" rating will appear soon. Whether it does or not doesn't matter since the "SL" rating makes it completely acceptable for use in your engine.

The only thing regarding the Rotella or Delo that is contrary to GM's recommendations for your engine is the viscosity rating. Since your engine is no longer under warranty, I don't think that this is really any issue. It's got nothing to do with catalytic converter longevity, anyway.

[Richard B.]

More Oil...

Thank you all VERY much for the excellent advise! I'll continue to use the diesel oil in the future. Now off to Bowling Green next week for the Regional, might as well "blow the carbon out" on the way!

Regards,

Rich #36956.....

[Jason B.]

Re: More Oil...

Rich,

Glad to see another Montanan here in this excellent forum. Have a great trip to Bowling Green.

Jason B.
(MIssoula)