Synthetic manual transmission fluid


Is there a synthetic manual trans fluid available that I can use in a '98 Civic. Increasing MPG is the only reason.


There is probably synthetic gear lube somewnere. If not at X mart then at a parts store.


Yes, there certainly is a synthetic available for manual transmissions. I’ve read of Royal Purple, which is really expensive synthetic, and it certainly improves mileage. It’s so expensive, though, that any savings in money may be a wash.

But if you’re interested purely in improving mileage, this stuff is probably a good bet. It’s also a pretty safe bet there are other, less expensive synthetics available.


Synthetic motor oil usually is a good choice for most manual transmissions…


Gear oil has an insignificant effect on a car’s performance, probably too small to be measured. We’re not talking about motor oil. Even the manufacturers of Royal Purple make no claims about increased mpg for their transmission product.

But go ahead if it pleases you. Probably can’t hurt. As for me, I’ll just stick to the stuff the car’s manufacturer recommends.


I know mobil 1 makes synthetic gear oil, it’s available in different weights. Check your owners manual (or with the dealer) to determine the correct weight.


I have switched to Mobil 1 synthetic gear lube in my last couple of manual transmission vehicles.

I think the difference in mileage would be too small to be easily measured.

Switching to a synthetic does make a very noticable difference in how smoothly the transmission shifts before it is warmed up, especially if it is cold outside.

The 75w-90 that my car requires sells for about $11/quart.


I would add that the OP should check the owner’s manual for any special requirements for this lube and make sure anything put in there meets or exceeds those specifications.

I also have noticed improvement in the feel of my transmissions when switching to synthetic. It is especially evident in the winter when the temps go sub zero.


Most big trucks today use synthetic transmission and differential oils. Lots of it. It costs 2-3 times what non-synthetic costs, but it has at least 3 times the life–around 500,000 miles. I wouldn’t use anything else in my manual transmission or differential, but I wouldn’t assume that it would affect mileage.


Check your owner’s manual to see if you are already using automatic transmission fluid in your manual trans. Auto trans fluid is quite thin and watery. If auto trans fluid is specified, then I seriously doubt that a synthetic will make any difference in mileage. If your trans uses 90 weight gear lube, then maybe.


Yes, tons, Amsoil, RedLine, Mobil 1, Royal Purple. Highly recommend for better MPG and wear