how long can used oil be 'shelved' and then evaluated?

[MattBrew]

Hi all. I love the site, it's extremely informative but maybe a little bit too much for me. I feel a bit overwhelmed with all the abbreviations and I still don't understand the differences between 5w-30 & 15w-40 and how to know which is which...

anyway, I changed my oil in my 02 TJ back in '03 @ ~ 20k miles and planned to due an analysis. I put some in a jar, sealed it up and I found it cleaning out the garage today. I marked the mileage and oil used (M1 10w-30 & M1-301 filter) Can this oil still be tested accurately? My mileage is now at ~ 36k and I'd like to run two tests to see a history. I really didn't believe that synthetic could be run longer than dino so I would like to see how many miles I can go.

 

[MattBrew]

just wanted to add that I am looking to go long changes 10k+ if possible. It get's 95+ here in the summer but rarely drops below 30 in the winter. Other possibly pertinent info; The Jeep sees a lot of off roading and has a 3 Speed auto tranny, so it runs 3000 RPMs at 70mph when on the freeway. 90% of my driving is below 60 though.

 

[MattBrew]

I do realize that. I changed the factory fill @ 1k with mobil1 and a regular size M1 filter and again @ 3k with a regular M1 then it's been every 3k since then with an M1-301

 

[Curious Kid]

Welcome aboard MattBrew.

As far as getting to comprehend all this interesting stuff, sit back and relax. For any new comer, myself included, it's like trying to comprehend a foreign language of sorts. Let your interests and curiosities guide you...possibly with a cup of coffee in hand.

Others will respond with knowledge concerning sample shelf life and OCI (oil change interval) potential...but I don't think 10K should be much of a problem with synthetics, however a UOA (use oil analysis) will be a more concrete guide.

Good luck and enjoy your time spent her at the BITOG!

 

[Curious Kid]

"See a lot of off-roading."

As far as reaching 10k OCI's with such operating conditions, you will have to managae air filtration as well as oil filtration, esspecially if things get dusty. Though not all the ingested dust deposits itself in the engine and oil, any that does is a mechanism for increased wear. Higher operating temps also lead to increased oxidation potential for the oil (causing the oil to thicken and favoring deposit formation), as well as the shear potential of the oil's viscosity index improvers which translates to the oil thinning out of grade.

From what little I know, I still think a synthetic oil would help you no matter, being that it is said and seeming evident to be naturally more resistant to oxidation and can be blended to not require viscosity index improvers, thus being more shear stable.

 

[1maniac]

Off roading = synthetic lubes IMO

 

[bighead]

3K would be no problem even under your conditions, but I'd do a few UOA's at 5K, just to be safe. With the offroading and high rpms due to the tranny, I think 5K would be ok....10K might be out of reach.