ATF in the oil


This is one of those times when it really is a friend who has a problem (no, really! I wouldn’t ever even have a reason to own ATF!)

I have a friend who has made a mistake an accidentally poured about half a quart of ATF in her oil filler. She asked me for advice, and I really had relatively little to offer, short of “you shouldn’t have done that”

I understand ATF is essentially oil based with higher viscosity and detergents, but what sort of problem can this pose for her? One step farther, she is about to drive through the nevada desert in the summer, so a breakdown could be much more serious than usual.

She has not started the car since the ATF went in. What would you all recommend?




No harm really, just change the oil if it bothers the owner to have that ATF in there. You could probably drive it that way forever or until the next oil change and not worry. A lot of people used to use some ATF in their engines on every oil change.


A lot of folks are near-paranoid about having anything added to the oil that isn’t supposed to be there. You may get plenty of advice recommending a complete and immediate oil change.

I think this is hardly necessary. Your friend can continue to drive as-is with little worry. But since an oil change is done regularly anyway, and it is not expensive, it is in her best interest to get her next oil change ahead of schedule. Advice her to do so when next convenient. Maybe in a week or so.


Thank you all! I’ll be passing this info along to her!


Some people actually put a half quart of ATF in there oil on purpose. It helps clean out the engine. I personally don’t recommend it, unless I’m trying to desludge and engine, but a one time accidental addition shouldn’t do any measurable damage.

If she hasn’t started it, then the ATF will still be in the oil filter. She could just take the filter off, drain it and refill it with motor oil. The residual ATF will not hurt anything.


The ATF is in the pan Keith not the filter. Tell your friend not to worry.


It probably won’t do any damage in the short term. Personally, I would change the oil again, but that’s just me.


It will be fine, Marvel Mystery Oil (a cousin to ATF) was once a popular additive at oil changes. A 1/2 qt. isn’t going to bother anything. It will slightly thin the oil assuming a 4-5 qt. capacity.


Oil filler not oil filter.
I think the OP’s post was misread in this case.