Wrong gearbox oil, will I have done any harm?

[Tom W]

I decided to change the gearbox oil in my S2 yesterday. It has the standard Jag synchro gearbox. The chassis plate said 20w50, the workshop manual said EP90. I remember reading on here a reference to the manual being incorrect, so I used 20w50.

Now, problem is my car has had a replacement chassis plate at some point. Presumably because the original was corroded. I have the original in the history file, so for piece of mind I checked what that said when I got back from the workshop. That says EP90!

So clearly, I’ve used the wrong oil and will now change it. Question is, will I have done any harm in the 25miles I drove back home from the workshop? For what it’s worth, the gearchange change felt the same as normal, and if anything the box was a bit quieter in neutral (less layshaft rattle), though that might be down to the correct quantity of oil, rather than the grade.

This is doubly frustrating as I’ve now used up some of my spare engine oil which I would have undoubtedly had to tip into the engine at some point and I have to repeat the job. Anyway, off to the motor factors to buy some gearbox oil....

[johnetype]

No, you will not have done any harm and nor would you have done if you'd driven 2,500 miles.

The different possible gear oil options for putting in this gearbox will affect noise, synchro effectiveness, mpg and the service life of the oil itself but none of them would make a significant difference to the amount of wear to the gearbox. The one thing that significantly affects the amount of wear in a gearbox is no oil.