I became an anorak when I decided to change my gearbox and diff oil recently! The recommendation for the diff (on this forum and elsewhere) without a LSD, is fully synthetic 75W/90. My 1.9 fits this category and I used 1 litre of the Carlube brand from GSF. However, I noticed that on the container it stated that it could also be used for cars with a LSD??
The recommendation for Z3s with a LSD (both on this forum and by Castrol) is fully synthetic 75W/140. Castrol seem to play a dominant role in terms of choosing BMW lubricants which means they are either the leading experts or have very good marketing managers. My understanding is that the 2.8 has a LSD but you need to check your original vehicle specification to be sure. For the larger engine Z3s I’ve seen diff oil capacities of 1.25 – 1.75 litres mentioned on this forum.
Choosing the right diff oil was simple compared with getting the right gearbox oil! My local Bristol BMW main dealer told me it is essential to check the label near the gearbox filler plug. According to Castrol it seems you can have an orange label (ATF oil), green (special oil?), two variants of yellow (MTF-LT-1 or MTF-LT-2) or no label (I’m not sure what oil that requires). There is more information on this forum about this topic from Mike Fishwick. The 2.8 gearbox is different from the smaller engine 1.9s such as mine. Research I did, suggested that BMW kept changing the oil specification for the 2.8 gearbox as some customers in cooler parts of the world found the gear change a bit stiff – I don’t know if that’s totally true or not but I do know that ATF fluid is recommended for some of the gearboxes. I’ve also seen some of this forum say they just stick in 75W/90 and all works fine.
Clear (as mud) now?