Does oil really go bad after 1 year if it was previously opened? i see online that its 1 year once opened, and 5+ depending on the type if sealed. for example I buy 1qt oil for small engines that need 1/2qt, so from what I've read here id wait 2 years to change the oil since it won't hit the hours, but if the oil is going bad in a year should I just do a change in 1 year to use it up?
Does oil really go bad after 1 year if it was previously opened?
- Thread starter Ang
- Start date
no
Not if you the cap back on the bottle and close it. I also store mine in my basement, which pretty much stays close to the same temperature all year. That hedges the bet a little.
Olive oil does.
What are the small engines for? If they are lawn mower engines, you should change oil out at the end of the season anyway, in spite of lower hours. That way it only takes you 2 seasons to use it up. And no, it won't go "bad" if closed up. FWIW, I use the same oil for my Euro cars in the mower and pressure washer so always have fresh stuff on hand.
Here is a previous thread where I linked a list of other previous threads on this popular topic:
https://bobistheoilguy.com/forums/threads/does-oil-go-bad-after-time.379209/
https://bobistheoilguy.com/forums/threads/does-oil-go-bad-after-time.379209/
4wd
$50 site donor 2026
^^ This ^^ … and in the south where my lawn is still green -
(Soon full of leaves) - I change spring/fall … 15W40/10W30
(Oil filter yearly) …
Right now its just a generator that I'm talking about for the 1/2 quart per oil change. its a portable generator, I never need to use it, so it will never hit 50 hours. so I planned to do it every 2 years instead of 1 from what I read here.
Thats talking about 5 year old oil, not brand new oil thats just been opened.
Oil is not hygroscopic like brake fluid. It’ll be fine in the reclosed container setting on a shelf in the garage for a year.
Also I think you saying you go 2 years on oil changes but you’re worried about the remaining unused oil gong bad. Wouldn’t logic dictate that if the unused oil in the bottle is bad within a year then same used oil in the motor would also be bad?
Also I think you saying you go 2 years on oil changes but you’re worried about the remaining unused oil gong bad. Wouldn’t logic dictate that if the unused oil in the bottle is bad within a year then same used oil in the motor would also be bad?
The oil in my seldom used Peterbilt was still good after 3 years in the engine.
Nope. I Had a box I had forgotten about when we moved 5 years ago. Had a few quart bottles half full that were probably 7-8 years old. Perfect, needed to change oil in lawn mower anyway! Shook them up and in they went.
People aren’t using crude oil though. It’s the additives that would be the issue over time.
Sure so what additive in oil goes bad? Most additives like the crude are naturally occurring minerals and chemicals. I don’t think calcium, boron, zinc etc. go bad.
This is a marketing gimmick so you buy new oil. Like I said in my original post, shake the bottle and pour it in.
Just my $0.02
The oil in your generator isn't going to go bad, either, unless you run it. Even test running for ten minutes every week, your oil will last a couple of years. It's the combustion byproducts that wear it out.
If you want to over-maintain that gen, pay attention to its fuel system and keep mice out of it. Those are the two biggest problems with OPE.
If you want to over-maintain that gen, pay attention to its fuel system and keep mice out of it. Those are the two biggest problems with OPE.
The additives will separate from the oil. Going bad is just an over simplified way of describing that the fully formulated product is no longer the same and may not be suitable for use. Not that the base modules have rotted away like a banana or something. But if you’re good with it - go forth.
I was thinking a change at hours or a year, like a car, but everyone was saying 2 years is fine, so I planned to do that. What do you think?
It's a small 1800W portable generator that stays inside, and I try to give it like 20 minutes every few months.
