I purchased a '92 500SL w/44k this spring which was serviced by dealer who used Pennz 15-40. I was looking at oils and most 15-40 are primarily for diesels. Will I compromise this engine by using a "Diesel" oil? It does have an SL rating. Thanks

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My evolution with Benz's
'77 240D
'87 420SEL
'90 300CE
'92 500SL 43k

No. Diesel engine oils (API service catergory CI-4) have a richer additive package of detergents, dispersants, anti-wear, and anti-corrosion additives, and the additive package is the most important aspect of a motor oil - not the base stock i.e. synthetic versus mineral oil.

Over the years these critical additives have actually been REDUCED in spark ignition engine oils as some of their combustion byproducts are believed to be harmful to catalysts.

I use CI-4 oils in all my cars, except the Merc, because its emissions tend to be high and it consumes about a quart of oil every 2K miles. If your car has low oil consumption and low emissions I would use a mineral base CI-4 oil and change it at the normal recommended interval (or more often if you prefer). For cars with FSS you can use a synthetic base CI-4 oil and go with the extended drain intervals.

Duke

I also use CI-4 oil in almost everything on the place except a few really new vehicles in which I use synthetic gas engine oil.

I drive my vehicles to ultra high mileage and when I take engines apart for any reason they are ALWAYS squeaky clean inside.

Good luck,