My buddy was changing his oil yesterday and overfilled it when pouring in new oil. So he loosened the drain plug to let some out, no big deal.

Problem is, he let just a bit too much out, and later tried to re-add that same oil using a turkey baster.

Unbeknownst to him, that turkey baster was last used about a week ago to siphon brake fluid from master cylinder, during a brake job.

TL;DR- could that small amount of old brake fluid from the turkey baster, mixed with 4.5 quarts of new engine oil, cause damage? Should my buddy change the oil again or is it fine?

  • Welcome to Motor Vehicle Maintenance & Repair! Commented Mar 2 at 4:34

1 Answer 1


At that amount, there's no chance of harm. Several ounces or more of brake fluid can certainly damage seals by swelling them.

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