PS - couldn't get the drain plug out with the correct sized tool - someone else had previously rounded the star hole. The filler took a lot of force, but the tool fitted the plug properly. So all I could do was top up.

The holes in the plugs on mine were for an allen key.

Came out very easily. Haynes manual says fill till the oil is just about to run out of the filler hole.

The reason I was curious was because, with the car on level ground, I got best part of two litres into mine.---Very strange.---:eek:

Hmm...have read conflicting views on the gearbox oil change. Some say DO NOT do if you're not having any problems; that's the advice my local mechanic gave me too, when I enquired about having it done this week.

I still haven't done it, although I bought 4 or 5 litres of the oil last month! I know I will only need 2 litres, but the bigger container was a bargain price! :)

So, what to do? My car has done 150,000 miles, and the previous owner did not change it, don't know before that. What is the downside to not doing it? I think, but cannot find it now, the gearbox oil should be changed every 90,000 miles...anyone care to enlighten me with their opinion/knowledge?

An oil change prevents problems from occurring. If problems become noticeable on a manual box, it is usually too late to correct them with an oil change.

Even with auto boxes, where the advice is often to leave well alone, the manufacturers now include an oil change at a certain mileage e.g. Mercedes. Also, the best practice adopted by the likes of Jaguar specialists on ZF autos is to use a machine that replenishes the oil with the gearbox being operated in order to remove all traces of the old oil from the torque converter.

I would always go with the view that one should do gearbox oil changes but only if it is going to be done properly and with the correct oil. Otherwise, take the risk of not doing it. If a mechanic advises not to change the oil on a gearbox, I would look to change the mechanic!

I think the general rule that not to change it unless you're having trouble isn't the best, and not the first time I've heard it.
Personally I'd say if you're having problems it's probably to late!
BMW Automatics a case in point, they were sealed! No drain plug fitted.
Sorry, but no oil lasts forever

Mines had it's changed every 4 years since it was new, so it's another job I need to add to the sunny-day list ;)

Thanks for the replies - I will go ahead as planned, and have it changed. Makes sense.

Normally when they say not to change the oil, they're referrring to a flush. But even then, that too could only cause problems on gearboxes/transmissions that already have problems by flushing out debris that was masking the issue already present. Changing the oil on a good gearbox will never hurt.

I have changed the oil in the gearbox and found (subjectively) that the shift was smoother.

Follow the official MGR service schedule and you won't go far wrong. ;)

Earlier schedule states to replace the manual gearbox oil at 90k miles or 6 years, whichever comes first, and the later schedule extends that to 105k miles or 7 years.

I use the earlier schedule, but each to their own. :}