Gear Oil Question

[Larry Davis]

At 58,000 miles I'm ready to change the front and rear gear
oil in my 2003 Forester XS (Auto).
The book specifies 75W-90 for the rear diff, and 80W-90 in
the front. I'd like to go synthetic with Mobil 1, but it's only
available in 75W-90.

My question: Would it be OK to use the Mobil 1 75W-90 in the
front diff ?? I'm thinking that it's so close it should be OK, but
Subaru's recommending a different weight makes me wonder...

I'd appreciate any thoughts/advice on this.

TIA

 

[AS]

I would not have doubts in using the mobil one, that is what i use with
no problems so far.

 

[Edward Hayes]

I've been using it for 102,000 miles without an issue. ed

 

[Carl 1 Lucky Texan]

At 58,000 miles I'm ready to change the front and rear gear
oil in my 2003 Forester XS (Auto).
The book specifies 75W-90 for the rear diff, and 80W-90 in
the front. I'd like to go synthetic with Mobil 1, but it's only
available in 75W-90.

My question: Would it be OK to use the Mobil 1 75W-90 in the
front diff ?? I'm thinking that it's so close it should be OK, but
Subaru's recommending a different weight makes me wonder...

I'd appreciate any thoughts/advice on this.

TIA

As others say, I don't think there would be an issue. I'm just writing
to say a lot of people also like Redline's products. I'm sure there are
several other brands that would be adequate.
http://www.redlineoil.com/

Carl

 

[MN]

At 58,000 miles I'm ready to change the front and rear gear
oil in my 2003 Forester XS (Auto).
The book specifies 75W-90 for the rear diff, and 80W-90 in
the front. I'd like to go synthetic with Mobil 1, but it's only
available in 75W-90.

My question: Would it be OK to use the Mobil 1 75W-90 in the
front diff ?? I'm thinking that it's so close it should be OK, but
Subaru's recommending a different weight makes me wonder...

I think you'll have a hard time finding a synthetic 80w-90 gear
oil. The properties of synthetic lube give it a wider spread,
"naturally" so to speak.

I've been using Mobil1 in both differentials of my Impreza
with no problems and highly recommend it. By the way,
Mobil (Exxon-Mobil, that is) is a great company. Yeah, they
do rip us off on gasoline, all energy companies do nowadays,
but Mobil has well tested quality products and a great customer
service.

I remember once buying a sealed case of their synthetic oil,
off the shelf at Walmart, only to find that it contains regular
non-synthetic oil :-O After some investigation by Mobil
I was refunded all my money, plus I got the case of
regular oil for free, and I also got an apology from them.
I thought the 20 or so dollars I spent were a goner.

MN

 

[Larry Davis]

Thanks to all for your advice - I'm going to do it....

 

[Body Roll]

How can you tell? Did your inner child tell you to do the oil analysis?

 

[MN]

How can you tell? Did your inner child tell you to do the oil analysis?

No, the sealed case of presumed synthetic actually contained
six blue bottles of regular dino Mobil oil. What kind of oil was
in those? I have no idea, maybe synthetic but I doubt it.

Anyway, Mobil was very helpful in a difficult and suspicious
situation. They conducted an investigation and refunded me
my money with an apology- supposedly they had a mess-up
at their facilities.

MN

 

[Body Roll]

No, the sealed case of presumed synthetic actually contained
six blue bottles of regular dino Mobil oil. What kind of oil was
in those? I have no idea, maybe synthetic but I doubt it.

Anyway, Mobil was very helpful in a difficult and suspicious
situation. They conducted an investigation and refunded me
my money with an apology- supposedly they had a mess-up
at their facilities.

Oh, I saw 5 qt. jugs which were about 2/3 the price of the boxed oil
and thought you went for those. I guess I'll just go for the jugs and
hope they poured the right stuff in.

I wonder if Cosco sells motor oil by the barrel...

 

[MN]

Oh, I saw 5 qt. jugs which were about 2/3 the price of the boxed oil
and thought you went for those. I guess I'll just go for the jugs and
hope they poured the right stuff in.

The mixup happened in 1997. As I recall the 5qt jugs were
not widely available then. I have learned from the experience
to always check the contents of any larger case, and also
to inspect the caps on jugs and individual bottles for signs
of tampering. Synthetic is expensive.

MN

 

[Edward Hayes]

I now check every oil container to see if its been opened. I was about
to buy 3 quarts of Mobil 1 gear oil and noticed that one of the little
1/4 inch long caps was a different color. I smelled all bottles and
there was a big difference. I suspected some jerk used the Mobil and
replaced it with motor oil or? I contacted Mobil and never heard
anything again. This was at Advanced Auto.

 

[S]

Hi Larry!

At 58,000 miles I'm ready to change the front and rear gear
oil in my 2003 Forester XS (Auto).

I don't know if the Forester XS is so equipped, but if it has an LSD
in the rear, that may require a different fluid. Something to do with
friction modifiers (or the lack thereof).
As such, it is probably worth doing a little additional research
before diving in.
I have zero experience with the Mobil 1 product, but I _have_ used
RedLine fluids, and have found their technical support guys to be
knowledgable and helpful. If you give them a call, they can probably
give you an authoritative answer re. the additive requirements; maybe
even tell you if the Mobil 1 product will be acceptable for your
application.
Hope this is helpful.

ByeBye! S.

Steve Jernigan KG0MB
Laboratory Manager
Microelectronics Research
University of Colorado
(719) 262-3101

 

[Edward Hayes]

The Forester "S" does have a rear LSD. Since it is self contained you
need no special gear oil other than a standard GL5. I use Mobil 1 in
my 2000 Forester S. I have about 90,000 miles out of 105,000 on the
Mobil 1 75/90 GL5.