Differential Gear Oil- Synth or Dino

[BillyG]

I have searched the forum here as well as Bob is the oil guy and still do not have a clear answer if I should use synthetic or conventional/dino gear oil.

I am leaning towards conventional because I hear that it seems to stick to the gears better than synthetic. Is that really true?

My Subaru WRX used synthetic in the diffs. Everything that I currently use is synthetic- crankcase, transfer case and power steering- because I was told that synthetic is the best or required.

:help:

 

[wlfpck]

I think synthetic is better overall as it is more heat resistant and some synthetics have more/better additives.

If you use a synthetic that meets the recommended Jeep specifications, I don't see how it would be worse. I have limited knowledge about Jeeps though.

 

[Aceofspades]

I plan on changing mine regularly so 80/90w regular valvoline is fine for me. I don’t tow yet and I don’t have anything special in the rear dif
In a Subaru or anything “performance” I would be all over synthetic.
You’re right. The info posted about oil type is really conflicting. Both points made , one sticks better and one is recommended by the OEM.

 

[HoosierJeeper]

I run conventional, 85w140. Sticks to the gears better and therefore keeps temps lower. I change it every other year/ 20-30k.

 

[BillyG]

I run conventional, 85w140. Sticks to the gears better and therefore keeps temps lower. I change it every other year/ 20-30k.

I see that my local O'Reilly's carries Valvoline 85w140 conventional so I will go with that.

Will I need the limited slip additive for the rear diff as well? That seems to be something I cannot find a clear answer on as well.

 

[Aceofspades]

So do you have a limited slip?

 

[HoosierJeeper]

07 wouldn't unless someone added one aftermarket.

 

[BillyG]

Okay, good to know that I do not have limited slip. For some reason I thought I did. I must have been thinking of a different model.

Thanks for the help!

 

[LibertyTC]

I made a semi-synthetic blend of my own with Lucas, which is good stick to gears stuff.
Freezer proof tested LOL !!
Link: http://www.jeepkj.com/forum/f196/rear-differential-gear-lube-61689/

 

[u2slow]

Basic 80W90 for me.

Pains me too much to dump $$$ oil when some issue comes up that needs the diff to be drained again.

 

[Damotee]

I use synthetic, 80W 140. I replace it about twice a year on average as I drive through water quite a bit where I live.

 

[Aceofspades]

Basic 80W90 for me.

Pains me too much to dump $$$ oil when some issue comes up that needs the diff to be drained again.

I hear ya. It wasn’t even broken in and I had to dump it to knock out the speed sensor... stupid thing

 

[duderz7]

I see that my local O'Reilly's carries Valvoline 85w140 conventional so I will go with that.

Will I need the limited slip additive for the rear diff as well? That seems to be something I cannot find a clear answer on as well.

If I remember correctly the Valvoline has a limited slip additive already in it, say it right on the front of the bottle. It won't hurt if you don't need lady, and works out great if you do.

 

[ltd02]

I used the Valvoline synthetic with the additive in it a couple times in my 02 with the trac lok but then switched to dino. Now I use dino in the 05 KJ, 98 Ranger and my 01 Outback. They all get the same 80w90 so I just buy it by the gallon. I don't know for a fact that the dino is any better but there is enough anecdotal evidence to go with the flow. I have to admit I'm a bit skeptical since if the dino sticks twice as well, but the synthetic is 5x better at fighting wear then who wins. I've never found any real data. I need some numbers :gr_grin:

"Lies, damned lies and statistics" - Mark Twain or Benjamin Disraeli you decide...

 

[tjkj2002]

I used the Valvoline synthetic with the additive in it a couple times in my 02 with the trac lok but then switched to dino. Now I use dino in the 05 KJ, 98 Ranger and my 01 Outback. They all get the same 80w90 so I just buy it by the gallon. I don't know for a fact that the dino is any better but there is enough anecdotal evidence to go with the flow. I have to admit I'm a bit skeptical since if the dino sticks twice as well, but the synthetic is 5x better at fighting wear then who wins. I've never found any real data. I need some numbers :gr_grin:

"Lies, damned lies and statistics" - Mark Twain or Benjamin Disraeli you decide...

Go to truehi9.com and click on "oiling system",then check out the pricing.

Up to $4000 for 1 single 3rd member,this is not the whole diff,just the gears and locker and they state no less then 3 times "85w-140 non-synthetic only".

 

[ltd02]

Where's their data? Maybe the owner owns stock in dinosaur juice. :emotions34:

I'll have to check out the BITOG forum must be some data there. I don't doubt it's possibly better but without data I'm skeptical.

BTW that truehi9 is a really neat website. Some real good gear **** there and they sure do use a huge font for the "85w-140 non-synthetic only".

 

[tjkj2002]

Where's their data? Maybe the owner owns stock in dinosaur juice. :emotions34:

I'll have to check out the BITOG forum must be some data there. I don't doubt it's possibly better but without data I'm skeptical.

BTW that truehi9 is a really neat website. Some real good gear **** there and they sure do use a huge font for the "85w-140 non-synthetic only".

Same thing for my Currie RockJock60 and Currie has been building diffs for longer then most on this forum have been alive.

 

[ltd02]

Same thing for my Currie RockJock60 and Currie has been building diffs for longer then most on this forum have been alive.

It makes perfect sense to me so I'm sure you are probably correct. There is probably data out there, but I'm in the numbers business so unless I see empirical data, I'm cautious.

Hell, even with numbers, a couple years ago eggs and red wine were deadly, coffee was worse than cocaine and salt would kill you instantly. Now all that has changed. Now people want organic foods grown with some ones feces as fertilizer, and prefer something covered in pesticides because they think GMO or gamma irradiated foods are gonna make them spontaneously spout another human out of their armpits. :help: confused2.gif

 

[tjkj2002]

It makes perfect sense to me so I'm sure you are probably correct. There is probably data out there, but I'm in the numbers business so unless I see empirical data, I'm cautious.

Easy way to test yourself,little costly and time consuming but if you want hard facts for yourself worth it.

Works best on a hot day,90+ degrees.

Drain rear diff and put in new dino gear oil(80w-90 or 85w-140,doesn't matter),hook up a 2500lbs trailer and blast down the highway at 75mph for 50-100 miles.Stop and take temp of diff housing(pumpkin and tubes) then pull cover and temp the carrier bearings,record temps.

let completely cool.

Now put in 75w-90 or 75w-140 synthetic gear oil in and make that return trip with trailer at 75mph for 50-100 miles and record temps at same spots as before.


You will see with dino gear oil that the whole rear diff is hotter since the dino gear oil transfers heat better(in a splash oiled system only) thus heating the diff which is exposed to cooling air.The syn oil will read much cooler diff temp readings since it has poor heat transfer in a splash oiled system.The huge difference will be the carrier bearing temps,the dino oiled bearings will be much,much cooler then the synthetic readings.

 

[ltd02]

Easy way to test yourself,little costly and time consuming but if you want hard facts for yourself worth it.

Works best on a hot day,90+ degrees.

Drain rear diff and put in new dino gear oil(80w-90 or 85w-140,doesn't matter),hook up a 2500lbs trailer and blast down the highway at 75mph for 50-100 miles.Stop and take temp of diff housing(pumpkin and tubes) then pull cover and temp the carrier bearings,record temps.

let completely cool.

Now put in 75w-90 or 75w-140 synthetic gear oil in and make that return trip with trailer at 75mph for 50-100 miles and record temps at same spots as before.


You will see with dino gear oil that the whole rear diff is hotter since the dino gear oil transfers heat better(in a splash oiled system only) thus heating the diff which is exposed to cooling air.The syn oil will read much cooler diff temp readings since it has poor heat transfer in a splash oiled system.The huge difference will be the carrier bearing temps,the dino oiled bearings will be much,much cooler then the synthetic readings.

That's a great idea. That would be the test I'd like to see. Heat=Friction=Wear=Bad!!!

I'm thinking someone must have documented something like this on the world wide web. I wouldn't be surprised if they interpreted the heat wrong and would claim the cooler diff temp with synthetic was good. Your interpretation is clearly much better and more relevant to wear. Maybe I'll get a chance to find something this weekend. Maybe some day (if I ever retire) I'd be able to do it myself. :gr_grin: