Does motor oil have an expiration date?

October 10, 2011 2:49 PM

Does motor oil decay/degrade in a previously-opened plastic quart bottle?

Found an old quart bottle of motor oil, half-filled in my car while cleaning it out. It's been more than a year since I opened the bottle. Will the oil still be effective to use in my engine?

If it matters, it's synthetic oil.

posted by honey badger to Travel & Transportation (4 answers total)

The oil is fine, as long as it doesn't have water in it or something, you can use it.
posted by tylerkaraszewski at 2:56 PM on October 10, 2011

Best answer: Oil is exposed to air, heat, agitation, etc., in your car's engine for months at a time. So no.
posted by weapons-grade pandemonium at 3:16 PM on October 10, 2011

Response by poster: Thanks for the (in hindsight) obvious answer.
posted by honey badger at 3:42 PM on October 10, 2011

You might have been thinking about brake fluid, which is hygroscopic and does not keep once the bottle is opened. Motor oil should be fine, unless (as noted above) it's been contaminated with something. If there's water in the oil, it'll appear milky.
posted by workerant at 6:24 PM on October 10, 2011