Does oil have a shelf life?
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DailyDrifter
The Slow and the Curious
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I dont think it does unless its left open or something, its been in the ground for millions of years.
A co worker says that's why they tell you to change your oil every 3000 miles or 3 months whichever comes first.
Quite honestly I couldn't see how oil would go bad from sitting. I always thought the 3 months was an estimated amount of time it would take to acquire 3000 miles.
Quite honestly I couldn't see how oil would go bad from sitting. I always thought the 3 months was an estimated amount of time it would take to acquire 3000 miles.
there are several facets to the question of oil life and in a short post i really can't begin to cover it all but i'll get you on the right track------oil designed for cars like most things except for rocks really can't really last forever but the conditions it is stored in can make a lot of difference------lets start with the base oil-------base oil types 1 and 2 (conventional) cannot last as long as type 3 (severely hydrocracked conventional sometimes marketed as "synthetic") and type 3 cannot last as long as type 4 synthetic------all base oil has somewhat lighter components that tend to evaporate before the heaver components and when that happens the base oil quality is compromised-------what causes evaporation????? heat and or storage in open containers would be the worst offenders------storage in lower temps and good quality sealed containers would surely make most BASE oils outlast you and your car-------HOWEVER motor oils are not just base oils and the better ones contain up to as much as 20% additives------addditives are another issue entirely-------while most additives are relatively stable it is probably safe to say that they would interact or breakdown much faster than any base oil------just how quick that might be still seems to be a pretty long time as long as the storage conditions are reasonable-------i have tested sealed cans of oil that are in excess of 10, 20 and even 30 years old and they seem to meet specs current at the time of their manufacture for additive percentages and viscosity--------there could be certain combinations of additives that could result in chemical instability but i personally haven't come across any in a lot of testing--------since motor oil these days is better overall than it has ever been there seems to be no reason to doubt that it will not have a rather long shelf life---------now what about "less than ideal storage"??????-------as soon as you open the bottle the degradation begins but its really slow-----pour it in your engine and time speeds up like you can't believe------interaction of the additives with different metals in your engine and even minute gasoline blowby remnants make the old "once a year" whether you drive it or not really good advice-------drive it once or twice for a short trip where it doesn't warm up completely and a destructive unstoppable chain reaction starts to degrade your oil and creat rust and deposits inside your engine-------byproducts of combustion create acids that really degrade your oil-------good grade oil can last a really long time if the engine is always brought to temperature and used regularly-------this of course is tempered by the condition of the engine-------oil lasts much longer in good engines as opposed to worn or poorly tuned ones--------short story???don't worry about oil on the shelf------its just fine------its the oil in your engine that is going bad--------of course you could always consider that the oil companies are changing their specifications every couple years-------current is SM-------GN's came out under SF--------technically that would make all your old oil "no longer current" -------does that make it "no good"-----not unless you have a new car-------i for one sure wish i had salted away a couple dozen barrels of old SG oil when it was available and cheap................RC
good quality oils contain additives that are in what is know as "chemical suspension"-------a rather complex condition to descibe but similar to salt in seawater or flavor in a pepsi-------below a certain percentage it takes quite a bit of "processing" to remove it from the base liquid-------i would NEVER consider any motor oil that required "shaking" before use after any amount of sitting on a shelf--------it will surely seperate under elevated temperatures and pressure creating sludge and/or clog your filter--------it would be a BAD choice--------if you have reason to suspect this of your oil (i don't think its possible with a quality brand name API rated oil) you should put some of it in a clear container and let it set for a while-------if it seperates at all you should seperate it forever from your car...............RC
Donniejr81
New Member
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If there is ever any doubt to oil not being up to par, I'd play it safe and just get some new stuff. A $40 oil change is better than sludging a $4000 engine. Old oil would make good lawnmower oil though...just my .02.
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I have read a LOT of your posts RC, could I please ask what oil you use? Not a flame at all! Just a simple question.
I respect all you have done for our TB community and hope to make it to an open house of yours some day soon.
Thanks
Ty
If you have a New bottle of oil and it sits on the shelf for 3 or 4 years the Additives in that oil WILL settle to the bottom. I have seen in several quality brands of oil. I doesn't mean the oil has gone bad, it's just settled! The additives will eventually fall out of suspension, its a fact. So to be safe i shake the oil a few times before put the oil in the engine. I prefer shaken not stirred. lol
sorry spooln------i didn't know if i should respond to this so i gave it a few days of thought------just because you didn't enjoy or fell asleep in chemistry class is no reason for everyone to accept bad advice------this shaking oil is total nonsense if you are considering quality oil--------how did you actually see this?????-------VERY few oil cans and or bottles are clear and allow inspection of the undisturbed bottom------if you don't understand the remainder of this post (i will keep it simple but scientifically factual) i suggest you pour some of your oil in a clear glass jar where you can put it in a safe place to observe it and check it in a few years------you will see that physics and chemistry are really fascinating and helpful when they are understood------the chemicals used in modern engine oil additives are not in particulate form------consider the well known metals such as zinc and phosphorous that make up the common additive everyone knows as ZDDP------when blended into oil these metals are atomically bound to other atoms in a specific molecular arrangement called zincdialkyldithiophosphate--------this chemical actually has 1 zinc, 2 phosphorous and 4 sulfur atoms bonded to each other along with multiple strings of alcohols-------each molecule of ZDDP has these individual atoms held in a bonded arrangement and none of the atoms are free to separate from the others nor can they bond to other like atoms and form particulates------ All other true PCEO (passenger car engine oil) additives incorporate organic chemicals----these additives will dissolve and bond to oil molecules which are also organic molecules------this is a characteristic known as oleophilic meaning "oil attracting"-------formulated PCEO is a homogenous liquid solution------this means that differing fractions cannot settle out-----in order to seperate any constituent substances out of PCEO you would have to perform a chemical or physical alteration to the oils structure-----such a process would be to lower its temp below its precipitation point in which case you could filter out any precipitated waxes or you could boil the oil and capture different distillate fractions-----it would also be possible to chemically process the oil to cause precipitation of certain substances---------but sitting undisturbed on a shelf??????------not a chance!!!!!!-------thats why you are never gonna find "shake before using" on any quality engine oil bottle-------there are a couple exceptions-------there is a certain chemical known by several names one of which starts with "T" that some folks just love to put in oil and sell on TV infomercials-------the company that invented this marvelous chemical actually lost a law suit to prevent its use in PCEO since it is generally bad for use in a car engine------but that doesn't stop markineers (my term for marketing types that think they are engineers) from making and selling it------- the folks that aren't technically educated are their victims--------this stuff is actually ground up solid particles and they form what is technically a "suspension" meaning they will eventually settle out because they are NOT miscibile in oil------most of this stuff (sold under several names) actually states on the bottle to "shake before use" but i am sure you don't use this stuff...........RC
