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#2332426 - 07/30/11 01:23 PM Does synthetic oil get "old"?
makiman Offline

Registered: 11/28/09
Posts: 3
Loc: Illinois
I use synthetics (Amsoil) in my cars and small engines but some of these motors do not get a lot of use. Oil manufacturer's typically state xxx miles/x months as oil change interval. If the motor is not close to the mileage recommended change interval does the oil really need to be changed based on time elapsed between oil changes alone?

Does synthetic oil "age" (deteriorate) without use?
Do the impurities trapped in the oil deteriorate the oil without running the motor?
Is it a moisture problem?

Curious about this as between autos and small engine equipment I have 6 crankcases to feed and I would hate to waste money on excessive synthetic oil changes due to time intervals alone.

#2332451 - 07/30/11 01:57 PM Re: Does synthetic oil get "old"? [Re: makiman]
cancov Offline

Registered: 06/13/11
Posts: 738
Loc: North Carolina
It depends on every application. For example, our small engines get changed once a year, in the fall before the winter set-up. We don't put synthetic in these engines because they do just fine with conventional for this OCI(oil change interval) and synthetic would just be overkill. Remember, extended OCIs are only beneficial if they save money by not having to change oil as often.

In passenger cars and trucks, again it varies on driving conditions. A good "rule of thumb" is to stick closely to the manufactures recommendation. Synthetic oil is capable of longer OCIs but more information about your application and driving conditions is needed.

To your questions:
Synthetic does "age" but not to the degree that conventional breaks down.
Impurities are suspended in the oil. Oil does neutralize acids in the sump, but it sounds like your asking in regards to an engine that sits up and doesn't get ran. If you search around, you'll see that the consensus on vehicles that sit up is to change the oil before the vehicle is scheduled to hibernate.
Moisture is a problem and can only be rectafide by running the engine on trips at operating temperatures of 10 miles or more. This burns off that moisture.

Welcome to BITOG, cafeful, you'll have a stash of oil and be telling your friends about oil and they'll look at you like your a huge dork.
'11 Toyota Corolla, Corolla MPG
'86 Mazda B-2000

#2332489 - 07/30/11 02:41 PM Re: Does synthetic oil get "old"? [Re: makiman]
chubbs1 Offline

Registered: 06/09/10
Posts: 4574
Loc: Merritt Island FL, USA
Oil breaks down and deteriorates at different rates as stated above. In your situation it is better to have synthetic over conventional. Those are not ideal conditions and both will break down so don't leave any oil in an engine too long. To all of those questions.
1. Does syn age without use? Yes it does, the more it was used before "dormant periods also applies. ie. more use = more blowby = faster deterioration.
2.most impurities/insolubles are just held in suspension until the next change.
3.Moisture IS a problem more-so affecting gasoline with ethanol, most moisture will burn off with heating the oil up to proper running temp. (ester oils are more prone to moisture retention over LONG periods of inactivity).

What options. Keep on using PAO syn like Amsoil or using conventional oil. Personally I would use conventional and change more often. That is a personal opinion placing myself in your situation. Amsoil will be better for very cold temps. if that is an issue. My lawn equip runs better on QSUD than AMSOIL.
'12 Charger SXT
QSUD 5w30 OEM filter

'12 Charger SXT
Edge FST EP 5w30 OEM (Mine;)

'11 Hyundai Sonata GLS
QSUD 5w20 OEM Filter

#2332497 - 07/30/11 02:48 PM Re: Does synthetic oil get "old"? [Re: makiman]
mechtech2 Offline

Registered: 09/05/06
Posts: 19479
Loc: Chicago Area
I'd use dino. They are very good now.

Also consider the option that you can change the oil twice as often, still save money, and have fresh oil .

#2332543 - 07/30/11 03:34 PM Re: Does synthetic oil get "old"? [Re: makiman]
makiman Offline

Registered: 11/28/09
Posts: 3
Loc: Illinois
Thanks all.
All good advice to help with the OCI for my various applications.

The motor that concerns me the most is the Kawasaki 290D in a Deere Gator. 290d's are good industrial quality motors and it has the optional oil filter kit which extends the OIC. Even though it's used in the winter to plow and the summer for all kinds of stuff I won't exceed the hour OIC recommendation in a year (takes about 1 1/2 years to hit the hour OIC limit). But when it is used it is used enough to heat the oil to operating maybe I won't worry. I have a jeep that's similar- used regularly but less than 8,000 miles/year.

#2332550 - 07/30/11 03:43 PM Re: Does synthetic oil get "old"? [Re: makiman]
cancov Offline

Registered: 06/13/11
Posts: 738
Loc: North Carolina
A quality conventional oil in the Gator changed in yearly intervals(Fall) should serve you just fine.

In the Jeep, in Illinois, bi-annual oil changes should work out fine, late fall just before winter and late spring/early summer.
'11 Toyota Corolla, Corolla MPG
'86 Mazda B-2000