Depends on the oil. If its cheap shit like you buy at Walmart, toss it out. If its decent like Amsoil, Redline, Mobil 1, etc, then they usually last about 5 to ten years, as long as it has been out of the sun and hasnt seen too much climate change. Oil's biggest enemy is water, and drastic climate change will cause condensation in some oils. The higher end companies nitrogen purge their bottles to prevent this.
You should be good to go unless it was opened and exposed to high humidity or something like that for a period of time after being open. Brake and automatic transmission fluids are a different story with moisture have a major effect on them, especially brake fluid. Oil is very stable and homogeneous. That is why it does so well as a friction reducer in your engine under high temperatures and pressures over long periods of time.
There are what is the term, keystones or something in petroleum based oils that will evaporate, IF it is not sealed.
I have not seen a cardboard tube can of oil since 1982 or 1983 so I doubt it's that old - meaning it's in a plastic bottle and was sealed - should be good for about hmmmm maybe another 1000 years or so...
If it was opened then check it for moisture, grab a mason jar and let it sit for a day.
When in doubt, recycle it...a tablespoon of water in a $1.50 worth of oil is not worth the long term damage it could cause inside an engine..
Many motor oils have a shelf life of about 5 years as long as it is sealed. Oils have some acidity and its biggest failure is moisture as previously stated by in da weeds. Usually the cheaper the oil the more likely it is to break down. Paraffin in the old motor oils would sometimes separate out. I will find out why. Like stated above the synthetics should last years and years.
Sean the bazillion year old stuff is crude not refined yet into the bazillion different things that can be made with crude.
Hell Yeah! A simple filtration an that stuff is all good to go! That is of course if you like Dinosaur oils. Me, I am pretty exclusive with my Redline for teh bike's, use the occasional Amsoil, and leave the Durablend from Valvoline for the truck's engine as all it's other oil using component's use Redline religiously(5 Speed, 3.92 Rear end, Transfer Case, Front Gear set). The radiator's use Redline Water Wetter as well.
Operating temperature for motor oils is well above the boiling point of water. Any moisture present would be purged the first time the motor warms up completely. More water vapor/moisture is normally present within a crankcase than is likely to ever be present in freshly decanted motor oil.
This is one of the reasons a mothballed vehicle's engine needs to be started up and run up to full temp periodically.
Filtration? Motors have oil filters. Happens anyway. Once a motor is run to the point where it needs its first oil change, it thereafter recontaminates the new oil with more particulate matter then you're likely to ever find in any fresh oil.
Filtration is key. As oil comes out of the ground after being there for millions of years,it has all the "goodies" in it and then some. Its all under pressure as we have seen an example off shore in the Gulf of Mexico. The crude oil is taken to the refinery where it is "fract" or cook. From this crude oil comes propane,natural gas,white gas,kersonse,avg gas,jet fuel,gasoline,diesel,motor oils,addivites,gear oils,waxes,road tar and burner,I problary miss a few. We go out to the oil patch and as drivers ,we tested the oil for purity and purchase it by writing out a bill of sale.If the oil has "free" water it will be at the bottom of the tank as water is heavier than oil. However,water can be mixed or homogus with oil. This takes a disperant to break down the oil/water molcules.Sometimes the water will fall or pecicapate to the bottom of the tank where it can be pull off with a pump.Other times it takes heat. This is what they are doing on the "Big" oil spill,to disperperse the oil.which in my humble opoion is wrong,oil is more collectable when bunch up. Yesterday I went to a self contained oil well site,when a large compressor motor has run ten,yes ,ten years with out a oil change. By pulling oil samples form the motor and changing oil filters on a regular basics,this was acheived. By the way,I got an idea as to pluggging the run away oil well,any takers?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ArcticLight</div><div class="ubbcode-body">There are what is the term, keystones or something in petroleum based oils that will evaporate, IF it is not sealed.
I believe the word you're looking for is ketone. You may also come accross the term in diet books; your body breaks fats down into ketones in the absence of available glucose as insulin drops and glucagon rises. And knowing is half the battle.
Wow, you guys are duly misinformed...
Has anyone ever blown a head gasket or cracked a block, where coolant has leaked into the oil. You think that coolant just boils right out of the oil? WRONG! Once water hits oil, it starts to break down the detergents and dispersants in the oil. Thats why when you blow a head gasket, your oil turns to milk. Yes, it is true, if you kept oil in a totally sealed environment and filtered it constantly, you would not need to change it for a very long time. It would need to be changed eventually however, because its chemical structure begins to break down after repeated heat cycles. As for your engine, the crankcase is not totally sealed. Old oil being cleaner than new oil is a crock of shit. Why do you think your oil turns black? Thats superfine carbon particulate that is less than .01 microns thick.