# Unused Automotive Fluids: How Long Do They Last? **URL:** \ **Category:** Factual Questions\ **Created:** [February 10, 2015, 8:58pm UTC](https://boards.straightdope.com/t/unused-automotive-fluids-how-long-do-they-last/712331 "2015-02-10T20:58:02Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![PastTense](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pasttense/32/14550_2.png) [@PastTense](https://boards.straightdope.com/u/PastTense)\ **Post date:** [February 10, 2015, 8:58pm UTC](https://boards.straightdope.com/t/unused-automotive-fluids-how-long-do-they-last/712331/1 "2015-02-10T20:58:02Z")
I have a moderately large number of automotive fluids in my basement, most of them not purchased recently and of quite uncertain vintage. By automotive fluids I am talking about things like motor oil, brake fluid, antifreeze, power steering fluid, transmission fluid, windshield wiper fluid, grease, carburetor or fuel injector cleaner, Stabil, gas line antifreeze… Is there any reason these aren’t good anymore? For example one I have heard with a possible problem is brake fluid which can absorb water if the container has been opened. Thanks. ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [February 10, 2015, 9:20pm UTC](https://boards.straightdope.com/t/unused-automotive-fluids-how-long-do-they-last/712331/2 "2015-02-10T21:20:47Z")
Regular motor oil (the non-synthetic type) doesn’t really go bad, at least not for a few decades, although any additives they put into it can start separating out after a while. I think they claim a 3 to 5 year shelf life for unused motor oil and transmission fluid because of the additive issues. Same for power steering fluid. Not sure about synthetic oils. You Joe Average basic antifreeze is 50 percent water and 50 percent ethylene glycol (or may be 100 percent ethylene glycol in the jug), which is pretty stable and again will last decades. There are some antifreezes that contain silicates, and those start to degrade after a few years. Brake fluid will last a long time if the container isn’t open, but, as you noted, if it has been opened then the brake fluid will absorb moisture from the air and will go bad fairly quickly. Your typical windshield wiper fluid will last for years as well, but again there are some fancier formulas out there, like some of the supposed water-shedding ones, that don’t last as long. Stabil has this to say: > [@](#): > > The shelf life of all STA-BIL® brand products is 2 years after the bottle has been opened, provided it has been tightly capped and stored in a cool, dry place. If the product has not yet been opened, you should use the color of the fluid as an indicator. If the product is still bright red, it is fine to use. If the product has turned to a very dark red (or brown) color, we recommend purchasing a new bottle. It will not harm anything if you use an old bottle of STA-BIL® brand, it just may not be as effective. ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [February 10, 2015, 9:26pm UTC](https://boards.straightdope.com/t/unused-automotive-fluids-how-long-do-they-last/712331/3 "2015-02-10T21:26:40Z")
In forty years of fixing cars, I’ve never run across any warning or advisory about the mentioned substances deteriorating in any way just from sitting. I have seen some greases partially separate, with some of the oil coming out of the goo. A recent thread describes an unopened washer fluid jug that had lost about half its contents, with the jug actually collapsing some; the consensus was that the alcohol managed to evaporate through the plastic. You’re right about brake fluid being hygroscopic, if not in a properly sealed container it will absorb moisture from the air. ---
**Author:** ![barbitu8](https://avatars.discourse-cdn.com/v4/letter/b/839c29/32.png) [@barbitu8](https://boards.straightdope.com/u/barbitu8)\ **Post date:** [February 10, 2015, 9:30pm UTC](https://boards.straightdope.com/t/unused-automotive-fluids-how-long-do-they-last/712331/4 "2015-02-10T21:30:42Z")
Good question. I have some unopened cans of oil which I bought in the days I changed my own oil. Don’t do that any more, but I wonder if still good to top off some oil if I ever need to. I haven’t burned any oil or leaked oil in ages, but one day my Honda may start burning some. I also have some unopened brake fluid. ---
**Author:** ![Lightray](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lightray/32/391_2.png) [@Lightray](https://boards.straightdope.com/u/Lightray)\ **Post date:** [February 10, 2015, 9:56pm UTC](https://boards.straightdope.com/t/unused-automotive-fluids-how-long-do-they-last/712331/5 "2015-02-10T21:56:55Z")
Most additive manufacturers do not provide shelf lives for their additives or blend packages. Some of the components – particularly detergents and dispersants – are quite stable, and can last years. Once blended into a finished fluid, however, the blend package isn’t as stable. Things start dropping out of solution. For a motor oil, I’d recommend 2-3 years at most. For transmission fluids, 1-2 years at most. This varies by manufacturer; antifoam, for example, drops out in \< 6 months, so a package high in antifoam will have a very short shelf life. Gas additives have very short shelf lives, less than 1 year. Windshield wiper fluid and antifreeze are pretty darn stable; just take a look and make sure there is no separation into different phases, or that there is no sediment at the bottom of the bottle. If you are storing additive fluids, keep them cool but not freezing, and sealed from exposure to air (or light, for some). ---
**Author:** ![jz78817](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jz78817/32/1028_2.png) [@jz78817](https://boards.straightdope.com/u/jz78817)\ **Post date:** [February 11, 2015, 12:50am UTC](https://boards.straightdope.com/t/unused-automotive-fluids-how-long-do-they-last/712331/6 "2015-02-11T00:50:51Z")
most of it’s been covered already, but I’ll add a warning about the antifreeze. If it’s the green stuff, the anti-corrosion additives are silicate based and shouldn’t be used in a modern car. Almost all newer cars use long life antifreeze which uses organic-acid anticorrosives. If you add the old green stuff to a new car, you’ve rendered the car’s antifreeze no longer “long-life.” ---
**Author:** ![PastTense](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pasttense/32/14550_2.png) [@PastTense](https://boards.straightdope.com/u/PastTense)\ **Post date:** [February 11, 2015, 1:54am UTC](https://boards.straightdope.com/t/unused-automotive-fluids-how-long-do-they-last/712331/7 "2015-02-11T01:54:34Z")
How do you define “modern car”, “newer car”? ---
**Author:** ![jz78817](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jz78817/32/1028_2.png) [@jz78817](https://boards.straightdope.com/u/jz78817)\ **Post date:** [February 11, 2015, 5:51am UTC](https://boards.straightdope.com/t/unused-automotive-fluids-how-long-do-they-last/712331/8 "2015-02-11T05:51:21Z")
> [@PastTense](#): > > How do you define “modern car”, “newer car”? anything post 2000. or, if in doubt, if your car’s factory coolant isn’t green. ---
**Author:** ![Saintly\_Loser](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/saintly_loser/32/4045_2.png) [@Saintly\_Loser](https://boards.straightdope.com/u/Saintly_Loser)\ **Post date:** [February 11, 2015, 2:57pm UTC](https://boards.straightdope.com/t/unused-automotive-fluids-how-long-do-they-last/712331/9 "2015-02-11T14:57:11Z")
> [@barbitu8](#): > > Good question. I have some unopened cans of oil which I bought in the days I changed my own oil. Don’t do that any more, but I wonder if still good to top off some oil if I ever need to. I haven’t burned any oil or leaked oil in ages, but one day my Honda may start burning some. I also have some unopened brake fluid. \*Cans \*of oil? I don’t think I’ve seen oil in a can in more than twenty years. Even if the oil is completely stable, motor oil has improved so much over the past few decades that I wouldn’t use really old oil. The API service classification code for current motor oils is (I think) SN. Anything lower than SH is classified as obsolete, and SE or lower has a big red “CAUTION” next to it on the classification chart (which is [here](http://www.pqiamerica.com/apiserviceclass.htm)).