Shelf life of Oil

SS MAYFLOAT

Admiral
Joined
May 17, 2001
Messages
6,372
My friends and I can't come up with an answer to this. Most vehicles require changing at regular intervals between milage or time, which ever comes first.<br /><br />If your vehicle doesn't get the miles put on, but time expires, why does this oil need to be changed? Does the oil that sits on the shelf at the store have an expiration date? How long has that oil been sitting there? Is it still good or has its time expired? <br /><br />Or is this a way to sell more oil? <br /><br />Thanks, I'm curious to know.
 

beniam

Petty Officer 2nd Class
Joined
Feb 2, 2005
Messages
113
Re: Shelf life of Oil

SS Mayfloat<br />Oil oxydizes when exposed to air, not when in a sealed container. In your engine, oil is exposed to air,and nasty byproducts from combustion, i.e. acids, water, and goodness knows what else. Running the motor long enough at operating temp helps to evoporate the nasty combustion byproducts. Oil additives do get used up in time,so they cannot neutralize the nasties, and will then start eating up your motor. <br />By the way, those oil change people have boat payments too. Be happy, enjoy life. Batavier
 

BoatBuoy

Rear Admiral
Joined
May 29, 2004
Messages
4,856
Re: Shelf life of Oil

Oil itself apparently doesn't go bad. It's the additives and contaminants that cause problems. I've been told that some naval vessels have oil in them that is decades old. They occasionally remove it and use on-board processes such as filtering and centrifuging, then replace additives, and put it back in the engine.
 

JB

Honorary Moderator Emeritus
Joined
Mar 25, 2001
Messages
45,907
Re: Shelf life of Oil

Vehicles that pass the time without making the mileage are usually short-trip and city used. If the oil stayed at operating temp, 180-200*, all the time it could go a looooong way between changes.<br /><br />Example: My MLs have oil condition (electrical conductivity) monitoring as well as mileage and temp monitoring. It's not quite real-time oil analysis but it goes a long way in that direction. Every time I crank up the 'puter tells me briefly how many miles it calculates I can go before I need to change the Mobil 1 and the filter.<br /><br />When I am making a lot of short (under around 30 miles) runs I usually get 5,000-7,000 miles on an oil change and filter. If I am traveling and keeping the engine at operating temp for 800-1,000 miles at a time I have gone as far as 14,000-15,000 miles before it asks for a change. In reality, I always change early, when there is still 1,000-2,000 forecast miles to go.<br /><br />Caution: This is Mobil 1 full synthetic oil, required by Mercedes Benz. Do not use my experience as a model of what to do with any other vehicle or any other oil.
 

LubeDude

Admiral
Joined
Oct 8, 2003
Messages
6,945
Re: Shelf life of Oil

If for no other reason, its acid buildup, (Another reason to run a synthetic) Synthetics have no sulfer content so they do not build up acids redily.
 

TheOilDoc

Petty Officer 1st Class
Joined
Sep 26, 2004
Messages
233
Re: Shelf life of Oil

By SSMayfloat:<br /><br />If your vehicle doesn't get the miles put on, but time expires, why does this oil need to be changed? Does the oil that sits on the shelf at the store have an expiration date? How long has that oil been sitting there? Is it still good or has its time expired?
The "time" portion of the change interval is intended for normal usage throughout that time period. It would not include an unused oil just sitting there. <br /><br />The "whichever comes first" part takes into consideration engines that might be used a great deal during the time period. In that case, mileage takes preference (and likewise). <br /><br />With the exception of automobiles, most engines base their change intervals on time. Acid build-up in oils is proportional to how long it has been used, and the conditions under which it was used. Most modern oils have reduced the effects of acid build up in oil.
 

one more cast

Captain
Joined
May 6, 2002
Messages
3,143
Re: Shelf life of Oil

I have a case or so of oil that my dad bought years ago. They are in cardboard cans and when opened have a milky white slime on the bottom.Is this the additives that have settled? I don't even dare use it in my old push mower.
 

LubeDude

Admiral
Joined
Oct 8, 2003
Messages
6,945
Re: Shelf life of Oil

Originally posted by One More Cast:<br /> I have a case or so of oil that my dad bought years ago. They are in cardboard cans and when opened have a milky white slime on the bottom.Is this the additives that have settled? I don't even dare use it in my old push mower.
Ebay it per can, there are collecors out there that will pick it up in a heartbeat. What brand is it?
 
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