Piston Slap: Engine Cleaner Edition

Brad writes:

Some years ago in an effort to quiet hydraulic lifters, I ran a quart of ATF in my Isuzu Trooper for 500 miles before I changed the oil. ATF supposedly has a bunch of detergents and this would clean out all the oil passages. I can tell you, the drained oil was the blackest I’d ever seen come out of one of my cars. It also seemed to help with the valve clatter, but didn’t completely cure it.

So here is my question . . . I’m getting close to an oil change in my 1988 911 Carrera, I was thinking of doing the same thing to it, to really clean out the engine. What do you think?

Sajeev replies:

Yup, ATF kicks serious sludge from an engine. The same is true for the famous Marvel Mystery Oil and a host of comparable engine cleaners. But that doesn’t mean I go out of my way to recommend them. Because I won’t.

I am wary of any high detergent “scrub,” mostly because the cleaning/desludging can create oil leaks around worn gaskets; or, it might dislodge a chunk o’ gunk which makes a new home on a crankshaft bearing. Worst of all, the increased friction of detergents means you run the risk of damaging your motor while the ATF circulates. Is it worth freeing a sticky lifter for this?

Of course, this is speaking in generalities. But using ATF on a fine running Porsche can be a serious financial burden on your wallet. Keep in mind that the motor in a Porsche is no (Isuzu) Trooper, and should be treated accordingly.

More to the point, you shouldn’t worry if you change oil on a regular basis: the motor will be tidy enough for decades to come.

[Send your technical queries to mehta@ttac.com]