Probably wasn't a great idea 75w140 gear oil

[Christos Adam]

So... I changed my broken transmission with another low mileage 5 speed during the weekend and since I couldn't find the NEO fluids that I wanted to get I went to Pep Boys and got their best gear oil.

I ended up paying $40 to get 2 liters of Royal Purple but the problem is that I got the 75w140 :ibrightdea:
When I realized my mistake , I was already under the car and it was too late to change it

Now the funny part is that since then I feel that there is an extra drag in the car when I drive it around... is this possible due to the thickness of the oil or it's just the placebo effect? Can the 75w140 be bad for the tranny?

[Q V]

I personally don't know, but some forum discussion (though it is about using 75w140 instead of 75w90 in a differential, not a transmission):

http://www.bobistheoilguy.com/forums/ub ... 887&page=1

It's Royal Purple, how bad can it be? ;)

If it feels draggy, just spend another $40 and put in the correct viscosity one - then you don't have to worry about it.

[Mako Koiwai]

A lot of folks like Redline MT-90 in their Miata Tranny's

It transformed Karen's. A couple of years ago we thought we were going to have to replace Karen's tranny. Switched to MT-90 and it's been like a new box.