Castrol Gearbox Oil in Citroen box

[dan chambers]

🖐️ It`s that time again to change the gear oil in my Esprit S3 and Turbo HC.  I have read a couple of older threads of what official oil to use in the Esprit and what type a specialists recommend.  Castrol have updated their range within the last year or two and have several to choose from.  The most important in my opinion is firstly the words Transaxle and Manual.  Maybe I`m reading too much into it but hopefully my mind can be put at rest so I can sleep easy tonight!

The same official recommendations used to appear for the Citroen and Renault boxes to use Castrol Manual TAF-X oil.  This is SAE75W-90, API GL4/5, VW 501 50 (as written on the bottle I still have).  The recommendation by Lotus circa 2012 (from another thread) was that Syntrans Transaxle 75W-90 oil could be used as the TAF-X was discontinued.  I`m not sure if this was a GL5 or GL4 or GL4+.  When TAF-X ran out of stock Opie Oils stated on their website that Syntrans Transaxle replaced this.  It now states that their Transmax Manual Transaxle 75W-90 GL4+ replaces the Syntrans.  The Transmax Manual is specified as a GL4+ and EP (extreme pressure) performance.  It is also to VW 501 50 as per the TAF-X.  The service manual and booklet recommends API GL5 however.  I imagine this is because there are EP requirements for harder metal parts mixed with softer metal components.  I have not had any problems for the last 15-20 years or so using TAF-X or Syntrans, so I must be doing something right!  When I do a search on Opie for my car it comes up with Transmax Universal LL 75W-90 GL4/GL5, though not the same VW approval.  Not sure what LL means.  Long life maybe.  Another thing I have noticed is that these oils are about twice the price they used to be, but these days you can`t do much about that. 

There are recommendations to overfill the gearbox to 3L for better lubrication for the synchro and needle bearing 5th gear on the primary shaft, rather than 2.25L, though I have never done this, I have read this can cause the oil to foam creating oil starvation.  I have gone a bit over the norm bolt hole level in the past, nothing too much.  I have also been told in the past that the gearbox doesn`t need that much oil to run, so not to worry if it leaks slightly from the rear plate.  I am open to doing whatever is best for my gearbox.    I may be reading too much into this and may have answered my own question by now.

I know there are different additives for a GL5 that can affect the softer metal parts causing potential corrosion, and going the other way with GL4 may wear out other parts faster.  This is all speculation from my point of view and I`m just a user of the product. The GL4+ seems like the right compromise? I was going to buy the Transmax Manual Transaxle stuff and be done with.

Cheers, Dan

 

[LOTUSMAN33]

I have used Redline MT90 in the past adding 3 quarts but find it really thin so want to try something else this time (Building two gearboxes currently).

I’m happy to try Castrol as like their engine oil if it works well?

 

[drdoom]

All Redline oils are leak prone due to the synthetic ester molecules' tiny size. 

[peteyg]

I've used Redline EP90 for the last 96k miles in my S2 and always filled to the level according to the manual.

Pete

[rgh0]

I dont believe the Polyol Ester molecular size is significantly different to any other lubrication oils. In any case fluid leakage does not really relate directly to molecular size but more to bulk properties of the fluid such as viscosity. 

In my experience with MT90 in my S1 esprit at least its leakage rate is similar to other modern synthetic oils.  If leakage is a problem then you have something  wrong that needs fixing. The common leak point in the Citroen boxes is the gear change shaft. You put up with it normally as its small or you fix it if you really want a totally oil dry rear of your transaxle.

The advantages of polyol ester base oil are huge in terms of thermal stability and lubricating properties so even if they did leak a little more they are worth it in my personal opinion but from my experience they dont. i will stick with MT90

 

cheers

Rohan

 

[jonwat]

I read many years ago that the chemicals in synthetic oil causes the rubber oil seals to swell so reducing leakage. Certainly when I first put Mobil synthetic in the Renault box of my Stevens' Esprit the drip that had always been underneath disappeared. 

[rgh0]

Most synthetic and mineral base oils actually tend to cause rubber seals to shrink so appropriate rubber swell additives are added as part of the formulation in quality oils to counteract this.  "High mileage" engine oils or supplementary lubricant additives have additional swell additives to help counter wear on seals by additional swell to minimise leakage from places like the rear main seal 

 

cheers

Rohan

[ekwan]

What lubricant does Citroen recommend? After all, they designed and manufactured the gearbox 

[jonwat]

5 hours ago, ekwan said:

After all, they designed and manufactured the gearbox 

That was fifty years ago. Even if the Citroen  recommended oil is still available oil technology has moved on a long way since then. 

[910Esprit]

The contemporary Lotus handbook (1984) recommended something called Valvoline X-18 MD SAE 80 GL5 (apparently X-18 was invented in 1939!)   I would imagine Citroen probably specified some 'ELF' product

Edited July 12, 2022 by 910Esprit