Automatic transmission fluid in 911 2.2 engine oil?

[924CarreraGTP]

I have what appears to be a slight rear main seal leak in my 2.2 liter 911 engine. Someone told me to put a small amount of Dexron automatic transmission fluid in the engine oil to lubricate and swell up the seals. Any ideas on this being a good or bad idea? The leak is not bad at all. It's maybe a few drops every week or so. I've even heard of old drag racers using it as an oil additive as well.

[M.D. Holloway]

I have heard the same - I don't think I would recommend it. It swells due to the esters in the oil but you run the risk of establishing an imbalance of the additive chemistry in the two oils.

Will it mess it up? Maybe or maybe not - it's a gamble.

[Steve@Rennsport]

JMHO, but never put any ATF in the engine oil,..........no exceptions.

If its dripping enough to contaminate the clutch disc, replace the seal (and oil pressure sender).

[LM3929]

ATF will not swell up your seals but it will clean the inside of the engine.

we use to use (in the real old days) and put one quart in when the engine was low or just before an oil change or for a Ford or AMC engine (see real old) to keep the hydraulic lifters quiet.


Lorne M.

[tctnd]

In the best case, which is highly unlikely, this would only be a short term band-aid. In the worst case serious problems could result. Don't do it.
regards,
Phil