Can 10w-40 oil use as manual transmission oil?

[Yc86]

Why waste the money! True that a 70W80 gear lube is around the viscosity of a 10W30 but with more additives, why go through all that trouble to make gear lube for yourself with gear treatment oil?

 

Just get some decent gear lube lah! Not expensive.

 

mmm... but why are the numbers different? i thought the numbers stand for the viscosity index of the oil?

 

shouldn't 70W80 be much thicker than 10W30?

[Trex101]

Recently, I put in 75W-90 gear oil into my old civic and the synchros crunched like hell. Read the maintenance manual and recommended viscocity of 10W-30 or 10W-40. Drained it off and refill up with motor oil 10W-30. Cruching stops. Shift silky smooth too. Will monitor sometime to see if any problem comes up

 

One problem with using engine oil as MTF are their lack of anti-wear and EP additives. It will increase wear and scuffing on your gear.

[Genie47]

70W80 is around the same viscosity as 10W30. Just look at the chart I linked. Gear oil viscosity need not necessarily be thicker just by looking at the numbers.

[Genie47]

Gear oil is usually not subjected to a lot of stress like engine oil. Pretty much safe in there. No combustion products to defend itself against. It should last as long as 2-3 timing belt changes. Synthetic even better. Some people like to change it yearly, some don't. Up to you.

[Trex101]

This is a good read comparing gear lub & motor oil from redline tech.

http://www.redlineoil.com/whitePaper/13.pdf