Club 80-90 Forums

Time to change the oils in the Syncro.

Have read the Wiki on this. There seems to be so many different recommended viscosity ratings quoted in the Wiki that i'm now not sure which to go for.

The redline stuff is too expensive for me so i'm going to be using Comma oil probably.

Will Comma's 75w90 GL4 or 75w90 GL5 be best?

Does the diff and gearbox take the same oil? Again the Wiki quotes a number of options.

Can of worms again...

Aidan might be along with something he has found... but we have yet to test it..

I have used the comma GL5 75w90 in my 2wd for 6 years... its covered 200k+ km in that time... it is showing its age, but I think thats mileage rather than the oil...

I have tried a GL4 and GL5 rated oil.. so assuming its ok for GL4 use as its duel rated.. but cant get confirmation on it... it worked well...
I have also seen a GL4+ I could use... and that prob meets the requirements quite well...

Comma semi-synth GL75-90W, especially in winter for slightly better gearchange. Worth reading the 'slow-into-2nd' Wiki article too... think its actually called.. Gearchange Reluctance

Ah! Here 'tis

--Its worth pointing out the best oil in the world (that'll be Redline MT90 then)--wont put back worn metal-- if yoove got crunching gears synthetic oil will make it change better but if yer box is on the way out I doubt if it'll make it last much longer--

About to try Millers racing oil, fully synth 75w90, half the price of Redline.
Millers reckon their oil can be used front and back, whereas Redline go MT90 rear and 75W90 front.
I figure you can use GL4 in the rear and front as there's nothing in the front that has a problem with GL4, whereas the special brass syncro rings don't like GL5 apparently.
I don't know anything though, all supposition.
I run cheap comma GL4 with a shot of Molyslip in one rear box, Redline in another, both work, both whine a bit, both weep a bit, both over 100k miles, both rebuilt in past one by persons unknown, one by Dave at Shiplake.
Might know a bit more when finished building this box and fitted it and run it for a few years.

Millers reckon their oil can be used front and back, whereas Redline go MT90 rear and 75W90 front.

Think MT90 is used extensively in the US and recommended for the transaxle, MTL is a bit thin, though I've used it.

I really think that synthetic GL-5 would be OK for the transaxle...

Interested to see how the Millers pans out though

GL5 that has been formulated specifically to avoid the "corrosion" problem that is supposed to happen.. is thin on the ground, I know of only 1 manufacturer that actually states that in there literature.. and I have not been able to get any so far!!!!!!!

I have a feeling thats what the dual rating GL 4/GL 5 is about, but cannot confirm..

Like I said before.. I have been using the comma SX75w90 GL5 in my 2wd for the last 6 years and the box has spent a lot of time at hight speeds.. (70-80mph for literally hours) in hot weather.. so when the box comes out, we shall see whats been eaten and if its a real problem..

I have a feeling that the addatives were not understood as well 20 years ago when the oils were specified for the syncro.. things have moved on!!
I shall be with Aidan on the Millers oil... They have a good reputation.. in fact, got a spare 5L? we'll do an oil change on the Audi!! it could do with fresh oil... 18 year and 265,000km.....!!!!