Old diff oil

[DragonZ4]

Planning to change the diff oil on my 2005 e85. Pretty sure its not been done so its going to be 17 year old oil in there.

Found some unused and factory sealed Castrol axle oil in the back of my garage dated 2014 which is suitable for the diff.

I never got round to using on a previous BMW. Just wondering if this is good to use or would it be passed its best as its so old?

No oil expert but I would have thought it can't be any worse than the old oil that's in the diff already?

Happy to buy new oil if that's the consensus, just seems a shame to have to chuck the unused stuff in the oil recycling down the tip if its still going to be ok!

 

[DMike]

An amateur opinion mostly echoing your reasoning... Several vendors often quote five years shelf life for unopened oils but there probably isn’t an absolute best before date when the oils go bad. I agree with your reasoning that the diff has older oil anyhow. Did my 2005 recently and old oil didn’t look that awful.

 

[Nick W]

For the small cost involved, take it to the tip and put new oil in. There is doubt in your mind so if it goes in your diff you'll be waiting for it to explode every time you hit the noise pedal.

 

[warmasice]

If it's mineral oil, I'd bin it. If synthetic which it probably is, then should be fine. BMW class diff oils as 'lifetime' so it's going to be better than the 17 year old oil you've already got.

 

[Zulu4]

I'd use it.
But then, I do eat out of date yoghurt 8)

 

[dtrandall]

I wouldn’t use 8 year old oil. The whole point is to replace the old fluid with fresh so do that. spend $20 and put in some redline diff oil. You’ll be glad you did,

 

[Thrustyjust]

Use it as a flush oil. Drain out the old, pump in the new and then a hundred miles later fit some new stuff.

 

[kis]

Use it as a flush oil. Drain out the old, pump in the new and then a hundred miles later fit some new stuff.

I like that
That way you can still make some use out of it

 

[SonnyA85]

I wouldn’t use 8 year old oil. The whole point is to replace the old fluid with fresh so do that. spend $20 and put in some redline diff oil. You’ll be glad you did,

It's not old oil though. it's just unused oil. i would say it's fine so long as it's been in a sealed container.

 

[enuff_zed]

I wouldn’t use 8 year old oil. The whole point is to replace the old fluid with fresh so do that. spend $20 and put in some redline diff oil. You’ll be glad you did,

It's not old oil though. it's just unused oil. i would say it's fine so long as it's been in a sealed container.

If it were simple oil maybe. But all the additives will degrade over time.

 

[SonnyA85]

I wouldn’t use 8 year old oil. The whole point is to replace the old fluid with fresh so do that. spend $20 and put in some redline diff oil. You’ll be glad you did,

It's not old oil though. it's just unused oil. i would say it's fine so long as it's been in a sealed container.

If it were simple oil maybe. But all the additives will degrade over time.

even if it's sat unused in a sealed container in a cool dark place? i have some that's 6 years old i was planning on using as a backup and i ordered a new one as well for the mechanic to use and whatever is leftover would be lumped together to use in future so I don't need to buy any more on the next change.

 

[Gregory_tolson]

Id buy new stuff. Diff oil is super cheap.

 

[B21]

Looks like Mobil and other oil manufacturers recommend 5 years maximum , if stored in correct conditions +10c to +25c…

https://www.mobil.com/lubricants/-/media/files/global/us/industrial/tech-topics/tt-lubricating-oils-greases-shelf-life-recommendations.pdf

 

[AveZ4coop]

6 year old oil is better than 17 year old oil. Oil companies suggest you bin any oil after 5 years, I wonder why that is???? The shearing action of the gears, and also heat generated, has far more effect on the oil viscosity than age.

In a nutshell, use the 6 year old oil.

 

[warmasice]

6 year old oil is better than 17 year old oil. Oil companies suggest you bin any oil after 5 years, I wonder why that is???? The shearing action of the gears, and also heat generated, has far more effect on the oil viscosity than age.

In a nutshell, use the 6 year old oil.

This.

 

[B21]

6 year old oil is better than 17 year old oil. Oil companies suggest you bin any oil after 5 years, I wonder why that is???? The shearing action of the gears, and also heat generated, has far more effect on the oil viscosity than age.

In a nutshell, use the 6 year old oil.

If you read the Mobil data sheet you would see that they differentiate between oil in storage and oil in use..

Oil in use plays to the oil’s formulation and help it’s life..in contrast to being locked up maybe in less than perfect conditions doesn’t help…

Clearly 5 vs 6 years is not going to cause a massive deterioration at that point…

But to come back to the point..you are only going to do it once ..

If you want to get some bale out of the oil..as others have suggested..if you drain the oil oil out then stick the 6 year old one in for a rinse then do the descent thing..

 

[DragonZ4]

Thanks for the replies, I'm going to use the oil, even if its just as a flush for a few 100 miles as suggested.

This is nothing to do with cost, just seems such a waste to bin good oil (If it was engine oil I would get some new oil without question).

Lets just hope the diff doesn't explode

 

[enuff_zed]

FWIW, if it were me I'd spend the few quid on new oil, then pour the old oil into my can of black waxoyl and paint it onto every exposed metal surface whenever I did any work on the car.

 

[Jellyfishfields]

FWIW, if it were me I'd spend the few quid on new oil, then pour the old oil into my can of black waxoyl and paint it onto every exposed metal surface whenever I did any work on the car.

I wouldn't be doing that with gear oil, it stinks.

 

[enuff_zed]

FWIW, if it were me I'd spend the few quid on new oil, then pour the old oil into my can of black waxoyl and paint it onto every exposed metal surface whenever I did any work on the car.

I wouldn't be doing that with gear oil, it stinks.

Seriously?
I sit on the inside and that's on the outside. No problem.