Piston Slap: Engine Cleaner Edition

Sajeev Mehta
by Sajeev Mehta

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]

Sajeev Mehta
Sajeev Mehta

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4 of 21 comments
  • PrincipalDan PrincipalDan on Jul 22, 2009

    I did use Marvel Mystery Oil in my old Oldsmobile with the 307 4B when it started to use oil around the 100,000 mile mark. It was burning a quart every 3000 miles and the Marvel stopped it. Kept it till 150,000 miles, but switched to Valvoline High Mileage Engine Oil when it came on the market.

  • ChuckR ChuckR on Jul 22, 2009

    1988.911.Carrera Look at that LN Engineering website oil discussion. They review why they prefer some oils that meet an older API spec and discuss additives to bring up the ZDDP (Zn and P)levels. IIRC, they prefer finding an oil that has the proper ZDDP levels rather than an additive. ZDDP has been reduced in newer formulations because it fouls the catalytic converters. News to me - my 1991 C4 always blew nearly zeros on the emissions check even in 2008. FWIW, their observations may apply equally to other high performance engines.

  • Andy D Andy D on Jul 22, 2009

    Some engines are more prone to collecting sludge than others. Short trips will also gunk up an engine. I favor 3-5 kmile OCIs I use the cheapest oil I can find. Current fav is Walmart Supertech 20w50 dino. At 330k miles , I pulled the valve cover on my 88 528e and found less than 1/4 cup of accumulated sludge. So I'm not buying into the hype about thin synthetic oils.

  • AuricTech AuricTech on Jul 22, 2009

    ~tongue-in-cheek~ Has anyone considered using KaleCoAuto's Engine Scrub? ~/tongue-in-cheek~