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Engine vs Gear Oil

glider

Veteran Member
Viscosity is measured by different scales for engine oil and gear oil. The two systems aren't directly comparable, number-for-number. Here's a reasonably accurate comparison between the two systems. Please remember that I said "reasonably accurate", as there is some overlap.

SAE Engine Oil ........ SAE Gear Oil

10w thru mid range of 20w = 75w

Mid 20w thru mid 30w = 80w

Mid 30w thru low 40w = 85w

Low 40w thru 50w = 90w

60w up = 140w


Looking at these ranges we notice that 50w engine oil is the same "real" viscosity as 90w gear oil. So it stands to reason that they might be substituted for each other. But remember that there are other factors involved than just viscosity. The ability to withstand shear, and additives designed for a particular end use are also important.
 
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Using engine oil in place of gear lube may have other draw backs besides missing additives.
Some of the additives in the engine may not be the best for parts in a gear box.
I know in a lot of equipment today they do use lubes that go in everything but I still wonder about it.
Till I see a real reason to change OIL in the engine, gear lube in gear box for me
 
Maybe, keeping the chart in mind is how Harley can say syn3 will work in all oil fills which we know is not the best for our bikes.
 
The Syn3 was a poor attempt first off as calling it a synthetic when it is a blend and not a synthetic at all but the lawyers argued the point backed by the $$$ from HD and won the case so it's referred to as a synthetic "blend" :D, the second poor attempt was using it as a gear oil just so the dealers could stock ONE product for all three compartments in big twins.

If Syn3 is so good to use in the trans (according to HD) why then did they come out with the Formula+ ?

Makes a person go Hmmmm!
 
The Syn3 was a poor attempt first off as calling it a synthetic when it is a blend and not a synthetic at all but the lawyers argued the point backed by the $$$ from HD and won the case so it's referred to as a synthetic "blend" :D, the second poor attempt was using it as a gear oil just so the dealers could stock ONE product for all three compartments in big twins.

If Syn3 is so good to use in the trans (according to HD) why then did they come out with the Formula+ ?

Makes a person go Hmmmm!

And now The MOCO is telling the dealers to get that junk out of the trannys and use a gear oil HMMMMM:p
 
The Syn3 was a poor attempt first off as calling it a synthetic when it is a blend and not a synthetic at all but the lawyers argued the point backed by the $$$ from HD and won the case so it's referred to as a synthetic "blend" :D, the second poor attempt was using it as a gear oil just so the dealers could stock ONE product for all three compartments in big twins.

If Syn3 is so good to use in the trans (according to HD) why then did they come out with the Formula+ ?

Makes a person go Hmmmm!

That can of worms was opened years ago by Castrol when Mobil 1 took them to court for calling their SynTec a full synthetic. The courts sided with Castrol since up till then noone had properly defined what a full synthetic was. Harley just pried open the can a little more:lolrolling.

I agree with many others here: engine oil in the motor, gear oil in the tranny.:s
 
ok I agree engine oil in the engine and gear oil in the gearbox,
i would like to do my own service to the bike, for the engine i like to use a multigrade oil 15w-40w (mobil, use it for my other bikes and cars also) but what kind i should use for the tranny and for the primairy chaincase and for the fork? can somebody help me out? because in the manual of HD they say lubricant part no98853-96 for tranny, but they do not say what kind it is
 
ok I agree engine oil in the engine and gear oil in the gearbox,
i would like to do my own service to the bike, for the engine i like to use a multigrade oil 15w-40w (mobil, use it for my other bikes and cars also) but what kind i should use for the tranny and for the primairy chaincase and for the fork? can somebody help me out? because in the manual of HD they say lubricant part no98853-96 for tranny, but they do not say what kind it is

Check here:

Oil Suggestions For Harleys - Harley Davidson Community

TQ
 
ok I agree engine oil in the engine and gear oil in the gearbox,
i would like to do my own service to the bike, for the engine i like to use a multigrade oil 15w-40w (mobil, use it for my other bikes and cars also) but what kind i should use for the tranny and for the primairy chaincase and for the fork? can somebody help me out? because in the manual of HD they say lubricant part no98853-96 for tranny, but they do not say what kind it is

From what I can find doing an internet search that pt # is a (75W-90) Trans Fluid
 
Mobile 1 75-90w in the tranny... The Best for everything duration...clean running...and stays quite the longest even in that HD stock 4th Gear ! Amsoil 20-50w in the Motor - there is no question...its the best. Put the Amsoil in the Primary too.
 
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