I'm just wondering if the gearbox oil temperature increases much during use, I'm guessing it shouldn't increase much as there shouldn't be anything in there generating heat.

The reason for asking this is that it was a hot day yesterday and my car was parked in the sun for the working day. When I left work the car was very warm but more noticably the gearbox was much nicer to use. This makes me think it could be better with lower viscosity oil.

Anyone care to comment?

It will warm up Eddy, it has to. I wouldn't drop the viscosity to much though, not with what you are running. How many miles has it done on the oil that is in there already? I noticed that after a change at 40k the box felt much smoother.

They do get hot inside, friction between certian components (even when oiled) will lead he heat as will transfer from the engine and its surroundings.

I usually fill boxes up with 10w40 engine oil if they are a bit sticky, makes the world of difference.

Wow! That is one hell of a change from the standard 75W-90!

Thinking some more about that drop, surely if you lower the viscosity, there'll be more wear occuring? I didn't think it would have the film strength required both at start up and more importantly when up to operating temp..... :confused:

The current oil has been in around 10k and is whatever the standard VAG stuff is.

Even after a long run the gearbox doesn't feel as good as it did yesterday.

This morning it was back to it's normal self.

I frequently get gear grind doing 2nd-3rd high rev changes and gearchanges take a little more effort than I think they should. However yesterday it felt great and even when I tried to provoke it I didn't get any gear grind.

Recommendations on specific oil to use would be much appreciated.

I'd personally go for something like Helix Racing 75W90, Millers 80W-140 (or 75W-90 if you aren't really pushing the gearbox to the limits of destruction), Mobil 1 SHC or the Motul Gear300

I've just filled the enquiry form in on Opie Oils website so I'll see what they have to say.

I bet they laugh out loud at someone claiming to have a 500bhp Octavia!!!

Just had a reply from Guy at Opie oils, I'm sure he won't mind me posting it and it may be useful for others. BTW can someone tell me how much I need?

The standard stuff from VAG is a 75w-90 synthetic of average quality. I had a look at the thread on Briskoda and looking at the power of the car something a bit stronger may be a better bet to cope with all the extra stresses and temps etc. No need to change to a thinner oil to get a smoother change, just improve the quality. I would have a look at the Silkolene Syn5 75w-90 ester based gear oil, very strong, very stable and also very fluid accross the temp range so should hopefully give you that easy gearchange you are looking for.

That's good of them. I've used the Syn 5 and it is good - got it filled with that at the 'Ring.

IIRC it's 2 litres for an 02J box

Opie have just advised I need 2.6 litres. So I'm looking at

It sounds very reasonable compared with the price of a gearbox rebuild! Just one word of caution; I've seen the gearbox oil capacity quoted as anything from 2.4 to 2.7l by various sources, so I'd go to 2 and bit l, then check for exactly how much more is needed.

Rover spec 10W40 oil for thier gearboxes as do quite a few others.

However I have only used 10w40 as a running in oil and never leave it in there fo rthat long (sorry I didnt mak ethat clear). However the chap that rebuilds our boxes for us swears by using regular semi synth motor oil and fully synthetic 75w90 is a waste of time but thats his personal opinion.

My Octy has done 100k and I doubt it have ever had an oil change. Would a flush help to remove the goo, and with what? Dave

Some good advice there

My Octy has done 100k and I doubt it have ever had an oil change. Would a flush help to remove the goo, and with what? Dave

I'd recommend changing the oil, not flushing it, just changing it. benefits are likely to include easier shifting, fewer missed shifts, and maybe even better fuel economy!

When I had the Z, the gearbox would get noticably lighter as it got hot and you could hear it turning when driving with the window open/roof down.

It had 2 gearbox rebuilds and eventually a new gearbox under warranty.

So I think its safe to say you shouldnt find a noticable difference in noise/feel - if you do, you're in for problems IMHO.