# Can 2 Cycle Oil Go Bad?



## Farmer Jim (May 21, 2004)

I've got several gallons of two cycle oil that is about 5-6 years old. I know gasoline goes bad with time, but what about 2 cycle oil? A couple of the containers have been opened, but had the cap on them and the rest has never been opened.


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## Gary (May 21, 2004)

I just checked my motorcycle 2 stroke oil and had pretrolium distilates in it, so my guess is I dont know. For a chain saw I wouldnt care, but for a boat, I wouldnt try it Jim. Especially the opened bottles.


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## JohnHumbert (May 21, 2004)

*In a word...*

...YES.

Especially if it's been opened.


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## goatchze (Aug 1, 2006)

Jim,

While I'm not 100% certain, I would guess that it should be fine. Lube oil isn't like gasoline; it's composed of heavier compounds that don't really evaporate in storage. Gas needs a very specific "vapor pressure", which means it needs the ligher components in there. Those lighter components will vaporize in storage and leave, making the gas "go bad".

I would guess that the oil should be pretty much the same as when you bought it, esp. the unopened containers.

However, I'm not that familiar with any "additives" that might go into 2 cycle oil and whether they can "go bad" or lose their effectivness (lose whatever properties they were supposed to add to the oil)

A safe course would be to mix the old oil with new when you begin using it.


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## redduck (Jul 26, 2006)

I agree with goat. I think it will be fine. Oil is a lubricant. They put additives in oil (depending upon use) for things like detergent free, rust inhibitor, etc. The basic oil is good. The oil in a 2 cycle is blended with gas to help lubricate during spark plug firing. It does not sit around a bearing for years. It is consumed with the gas.


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## JohnHumbert (May 21, 2004)

*Guys.....*

.... Outboard oil, especially 2-cycle oil, has been blended with additives that react with air and is designed specifically to break down over time. This is environmental stuff that has been added.

Even "old" oil in your reservior ON YOUR MOTOR will begin to break down as soon as it gets in contact with air.

Generally this is not a problem, as your oil gets consumed within a year. However, oil that has been around for several years almost certainly begun to break down.

In addition, each year the 2-cycle "formula" changes somewhat for the model year and gasoline blends that are being manufactored that year. This might not change much in 1 or 2 years, but if the oil is 5 years old - you can garantee it's not the 'optimal' formula for current blends.

I might use a sealed container that is a year - maybe 2 - old in a pinch. But I wouldn't take a chance on anything older and would prefer to use newer oil if it is available.

All that being said, you can greatly reduce the risk by mixing the "old" oil with "fresh" oil - if you don't want to throw the old stuff out, or you have a lot of it that respresents a significant cost.

New oil = $5
Engine Rebuild = $6000
New Engine = $12,000
Peace of mind = PRICELSSS!!


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## BonesNTX (Aug 14, 2006)

Some people use synthetic oil.

If you did have synthetic, age wouldn't be an issue.

I wouldn't use "old" petroleum oil for sure...AND, it would PROBABLY be fine. It's that PROBABLY part that dis-qualifies it for me.


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## Gary (May 21, 2004)

Most 2 stroke oils are a blend of natural and synthetics.

I just wouldnt trust it Jim. Not in an offshore boat, now way!


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## alant (Dec 7, 2006)

I'm not expert in this area, but I don't see how 2-cyle oil would go bad. I would agree some of the additives may not be effective, but I don't understand how they could cause problems. Gasoline goes bad over time because it absorbs water, particularly ethanol gas, and the gas and water separate causing direct injection of water with no gas or oil....not good for your engine I haven't read that oil additives have the same problem. And even if oil did absorb some water, it seems like the ratio of oil to gas would make it realtively insignificant. Oil is stored in an air tight container, unlike gas in a boat, so I don't see how it could absorb water. If you have an older engine and older oil, what's the difference in new oil with ineffective additives compared to the oil we used 15 years ago without modern additives? Am I off base? 

I'd love to see some official information on this issue, other than "buy our new oil to be safe". Anybody got a contact? I'm curious because I found a gallon of old oil in the back of my garage. If we're all keeping our oil that long, then we're probably not going fishing enough!


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## jeff.w (Jan 22, 2006)

This is not the official word by any means, but I asked our lubrication expert here at the plant this question. He is responsible for doing analysis of oil samples to diagnose equipment failures. His response was this:

2 cycle oil has a 5-6 year shelf life if unopened.


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## goatchze (Aug 1, 2006)

jeff.w said:


> This is not the official word by any means, but I asked our lubrication expert here at the plant this question. He is responsible for doing analysis of oil samples to diagnose equipment failures. His response was this:
> 
> 2 cycle oil has a 5-6 year shelf life if unopened.


That's what ExxonMobil says about their motor oil, including synthetic Mobil 1, so it sounds about right.


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