cam87

hi guys,


i want to change my rear diff oil to something better than the factory stuff. I will be using Millers fully synthetic nano 75w90 and on my previous cars i used a LS spec oil on my blob/hawkeye but the manual just says to use GL5 75W90 in the new car. Do i stick with the LS or do i need the standard 75W90 oil?




thanks for any help

drummog

I'm afraid you seem to have some problem with the factory fill. Can you provide a used oil analysis of previous STI diffs with the oil used to allow a judgement to be made on what issue you have with the standard fill.

I have to as yet see the results form a diff oil change that has reduced iron wear deposited in the oil or that shows the diff oil staying in spec for a longer mileage or time.

There are not better oils there are oils that have a specific feature changed but as always that will also change various other performance features of the oil and certain of these features will be reduced in efficiency. There is no action without a reaction.

The changing of the diff oil for one of the more expensive oils for a well now supplier on this forum may well give you a good feeling for doing it but unless you can advise the problem with the existing oil then what is the point.

cam87

Thanks for the detailed reply!


Well i dont have an issue with the factory oil exactly its more what i have planned for the car. The car will be remapped by the end of the month and the warranty for the egine/drivetrain will be out the window. I know with manufacturing costs etc they will put in an oil that is up to the job but wont account for trackdays as these will void the warranty anyway and this can be checked in the ECU. So my plan was to uprate the diff/gearbox oils in order to give the components the best possible chance i can as the car will be tracked.




Thanks

hedgecutter

iTrader: (5)

I found the Millers really noisy in my lsd rear diff on my hatch spec c, and oilman suggested Motul or Redline , as he had heard this from other customers

cam87

thank you for the advice

drummog

The standard cars has a torsen LSD that is basically a road car diff that has the a sealed limited slip capules that works by paddles moving in the viscous liquid in the sealed container, the liquid gets sticky when the driveshafts are going at different speeds ie when one wheel is spinning.

That causes the drive shafts to have less of a speed difference therefore the possibly spinning wheel comes under control. As the capsule is sealed it does not share the diff oil and these capsules are quiet and tend not to ******. Therefore there is no reason what so ever to change the stock oil as it is getting no wear from the LSD capsule.

The type C has a clutch type of LSD as it is a competition vehicle or has competition parts. These diffs are noted for their harshness at the limit and their they have different characteristics some chatter more than others. That requires a specific oil additive that reduces the chattering but is different for each diff. some need it others do not. It is basically not suitable for a car that is a road car that does the odd track day, they are added for those that want "The Best" when it is not better unless in real competition driving but people want to treat themselves to a fancy car! .

The oil you mentioned Millers is a very low friction oil and this is not always best for clutch type diffs and that may cause more chattering as you mentioned.

Sorry but the simplified nonsence the Oilman produces that A oil is better than B oil that is better than D oil that are all better than a cheaper oil they sell. is jut silly.

When I have challenged then to provide used oil analysises to prove their point they never produce the facts.

Further there are not realy better oils. There are oil that contain different base stock oils and different additive packages. Each one of these oils may well have an advantage in say better low temperature gear change but it may well then have more of probability of going out of grade sooner due to its make up or the additive package may well stop being as efficient later in it's life.

In the case the original poster appears to have a standard road car with a sealed LSD capsule, therefore apart from changing the fluids every one or two track days if that is needed as this is a similar price to doing a used oil analysis. I can see no advantage to getting a "better" oil as there is no published data to back up the "better" rather than "different" claim for the oil.

hedgecutter

iTrader: (5)

What exactly is wrong with treating yourself to a fancy car? Btw, the Millers was suggested by Ayln at ASPerformance,; you sound like PS Lewis_ but thanks anyway

drummog

Grow up Hedgecutter and do not quote me out of context!

I never said there is anything wrong with treating yourself to a "fancy car" so wind your neck back in.

The fact that someone recommended the wrong oil for a car as that specific oil does not have the necessary "clutch" type LSD specific friction modifier additives just shows it is difficult to find the correct oil for that specific application.

Don't shoot the messenger!

hedgecutter

iTrader: (5)

Ooh er, get you. Hatch specC has a different rear lsd from previous specC, and takes 75w90. That's what the jap handbook states, and that's what Alyn correctly recommended.

hedgecutter

iTrader: (5)

I must have misunderstood your fancy car comment, as you have misunderstood my attempt at humour! Nor do I doubt your knowledge of the workings of lsd's. But I can't grow up anymore, I'm too close to the grave section of life!!