I think it is more the casing - Torsens work in part by pushing outward against the case, and this is what seems to crack, more than the gearsets. But they will wear out, and heat up, and the thin gear oils will thin out. No 75w90 is close to the viscosity of a 90w at 100degC. None.

topcat7111 - your opinions notwithstanding, the facts about the actual viscosities levels of multi vis and straight weights have been measured, discussed, and analyzed ad nauseum in "the truth about 90w...". Quo vide.

What Honda does and what Ferrari does are completely irrelevant: it is illogical to attempt to infer anything, one to the other. You also should understand that what Ferrari supplies to street cars, and what they use to race are different.

many cars mfr's, esp gas hogs, use lighter weight synoils as factory fill so they can get the best benefit in the EPA economy and emissions testing.

 

I doubt this applies to Ferrari.....One of local member has a friends that owns a '97 F355...i was there when he open his hood and right there on the engine bay, to use 5w40 Shell syn engine oil and 75w90 shell syn differential oil.

 

the answer is evident...s2000 needs 90w, whereas ferrari only needs 75w because...

...the s2000 is a BETTER car. TAKE THAT.

 

[QUOTE]Originally posted by Road Rage
I think it is more the casing - Torsens work in part

 

What Honda does and what Ferrari does are completely irrelevant: it is illogical to attempt to infer anything, one to the other.

Why so??? They both have Torsen type limited-slip differential. They require GL-5 hypoid gear oil. They have more HP than torque. They both have high rpm. They're high performance sports car, except the price difference.

Now back to the weight of the gear oil...If a differential is not design to handle high amount of HP or torque, the best lubricant in the world can't save this inferior differential unit!!

This just my assumption, Honda on there part didn't do enough R/D on this little (mazda/kia) differential unit. Maybe this little differential unit just can't handle the power coming from the F20c, when driven too aggressively!! So, i doubt it has anything to do with the weight of the gear oil, we might just have a inferior differential unit!!

 

Having just changed the diff fluid to 75W90 Mobil 1 synthetic gear oil, should I drop that out and put a single weight 90W hypoid gear oil in there?

 

Sorry to bring this thread up again. I just went to Weseloh Honda down in South Orange County, CA and they only had the drum of the diff oil for their tech's to do service with. They offered to order the part, but why go through the wait when you can visit a local Honda Motorcycle Dealership? So I drove literally 20 seconds down the street to the Honda Bike Dealership and got myself a quart of 80W90 Gear Oil. Good stuff.

 

Take a look at RRs earlier posts (links at the top of the "Under the Hood" board). Oil serves more than one purpose in a gearset, and it's important to look at those factors.
Personally I use Amsoil Series 2000 75W90 in this car and the oil comes out clean after more than 7500 mi of hard driving.

 

I understand that, my point in making my comment was to say there are more than one ways of obtaining the OE gear oil. I generally assumed most people thought the oil was only obtainable through the dealership, but Honda motorcycyle dealerships have teh SAME EXACT oil available.

 

The OE gear oil is not the motorcycle oil. (That was a "lame" Honda response for Canada's cold climate in my opinion, and they never changed the Owner's manual specs either). I analyzed the OE fill, and it was a straight weight 90w gear oil of average quality. That is why i sought to locate, test, and make available the knowledge of research I did on oils that meet Honda's expressed spec oils for the diff: 90w GL-5.