Final Drive oil specs - is one of these better?

[Johnny248]

I have a bike with a separate final drive which consits of gears and bearings. There are no clutches. The gears have been changed from 12.1:1 to 8.4:1 ratio, and the bike has been pretty heavily modified. It originaly went 25mph, now it does a little over 70mph.

The factory manual calls for 10w40 motor oil. I am looking at two different oils, and trying to decide if one would be better than the other based on specs. I want to use something better suited for gears than a standard motor oil. Of course I want the best protection, bur at the same time dont want something that is so heavy that it could decrease efficiency. I have found these two oils which look like good candidates. The first oil is labeled as a gearbox oil good for use with wet clutches. The second oil is labeled as a gearbox and differential lubricant.

Oil 1

Density @ 20°C - .874
Vis @ 40°C - 108.8
Vis @ 100°C - 15.4
VI - 149
Flash Point - 230°C
Pour Point - -30°C

Oil 2

Density @ 20°C - .897
Vis @ 40°C - 72.6
Vis @ 100°C - 15.2
VI - 222
Flash Point - 200°C
Pour Point - -60°C

 

[spasm3]

Since no clutches, i'd use the second. The first one is really heavy when cold. Thats more drag on a small 72cc engine.

 

[tdi-rick]

I can say instantly that #2 is Motul Gear 300, nothing else I know has that VI and those specs.
Not sure what the first one is, but I wouldn't hesitate using Gear 300.

 

[Johnny248]

You are correct! Guy knows his stuft lol It is Motul Gear 300. That is what I am going with. Looks like some excellent oil. The fact that I dont have clutches or anything probably makes this a better option. From what I've read, it is an excellent Ester based oil, and the viscoity numbers look good as a 10w40 replacement.

The first one is Motul TransOil Expert 10w40. This one is one of their Technosynthese ester blend oils. It is also supposed to be excellent, but I think it is a little more suited for a gear box for a dirt bike or something with gear changes and clutches.