Engine Oil Additives

[Kent C.]

Any comments or suggestions with respect to using engine oil additives such as "Slick 50,", etc? Currently have 77K on engine.

6.5TD, K&N Filter, straight exhaust, turbo-Master.

Appreciate any input on additives--not only for engine, but also for diff(s), etc.

Thanks Much.

[CleviteKid]

Stay away from Slick 50, Duralube, and any such "miracle-in-a-bottle" oil additives for your diesel engine. The additives may gum up at the temperatures and pressures in the piston ring belt on a diesel, and screw up oil consumption, compression, and wear of the cylinder.

In my own engine, I use 1/2 bottle of STP red-bottle "Four Cylinder Formula" because it adds back the zinc dithiophosphate (ZDP) that has been taken out to meet emissions requirements. ZDP is sort of the miracle drug of oil additives - it is the best anti-wear additive known, and it also helps stabilize the base oil against oxidation and thermal breakdown. The disadvantage is you get some polymer viscosity index improvers that we don't need, but you get less of these in the red bottle than in the traditional STP blue bottle.

If you are using high quality synthetic transmission and differential lubes, you won't need anything in the tranny. If you have a limited slip differential, like my Auburn, you MAY need the GM "Limited Slip Axle Lubricant Additive", GM part number 1052358, available from your Chevy or GMC dealer. This will stop the clunking and popping noise and feel in your limited slip differential, if you have that symptom. If you don't have the symptom, you don't need the additive.

Dr. Lee

[Spindrift]

Doc,

Can I assume you're using dino oil in your truck's engine and that's why you add the ZDP? Or, put another way, If you're using a synthetic engine oil, is ZDP necessary?

[Kent C.]

Thanks Doc.

I'll be looking for the STP Red-Bottle as you suggest.

[CleviteKid]

Yes, you need more ZDP (IMHO) even with synthetic engine oil. Only the base oil is synthetic - it is the proper additive package that makes the oil work as an engine lubricant, and the government, in its infinite wisdom, has forced the oil companies to reduce the amount of ZDP they are putting in the oil. So far the PC Police are not taking oil samples to inspect for "excessive" (i.e. proper) zinc levels .

Dr. Lee