Quote:
Originally Posted by Pnut
So while DT40 helps more with metal wear in the motor, at the same time it's killing the cats faster? Would it not be more prudent to simply use a good full synthetic and be vigilant about short interval oil changes? Four cats x $xxx ea. = ouchy.
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Exactly how much ZDDP contributes to early cat failure is a matter of conjecture. If you blow ZDDP in quantities into cats, they do become poisoned and fail; that is a matter of fact. Unfortunately, the cats also fail, in large numbers, on cars that use oil with little or no ZDDP in them, implying that there is another element at work here.
By far, the biggest contributor to cat failures is thought by many to be cheap gasoline additives, which also contain levels of metal salts. Add in the fact that your car would have to be consuming a lot of oil over a prolonged period to get to the level of ZDDP that kills the cats, some very interesting questions arise; like is it the ZDDP from the oil, or is it coming from the fuels, which are blowing burnt additives into the cats constantly? Obviously, the gas additives would answer the how cars using oil without ZDDP ended up with dead cats, but the OEM's lobbied the EPA for relief on having to replace failed cats, pointing the finger at ZDDP instead, and the EPA bought their questionable logic.
In any case, replacing your cats is far cheaper than replacing your engine; believe me, I have had to do both for customers on a regular basis. Used cats out of wrecks are readily available and actually fairly cheap. And they can be changed in a driveway with simple hand tools. Swapping out an engine is entirely another story, particularly with crate short blocks costing more than most of these cars are worth.