Ok.. I went to my local shop the other day because I was changing out my derby cover on my bike.. btw its the 98 custom.. I walk i and ask one of the people behind the counter at the service/parts department.. where the primary oil was.. and they asked me if I was running conv. or synthetic.. and I told them synthetic. they said OK.. and handed me the a quart of the SE Synthetic motor oil.. I looked at them kinda funny and said you do realize that this is motor oil right.. and they said yeah.. they said that recently they "Which I don't know who THEY are.. " suggested using this instead of 75w-90 or whatever they suggest.. my question is.. has anyone else been told this .. and way the hell should I or should I not do this..

thanks
J

 

They must be smokin crack....stay with the 75w-90. I run the synthetic.

 

go read up on the oil threads in the self help section.

 

Why do you need fluid to change out the derby cover? Please don't think I'm being an a-hole...just curious.

 

Just changing out the derby cover you don't need the gear oil but while you're in make sure its a the proper level. I have heard of people doing this but i wouldn't do it but thats is just me. also buy your oils at the auto parts stores and save a little money.

 

There are quite a few people who run 20/50 in both holes.

Me personaly.........I'll stick to the 75w-90 in my gear case.

I use mobil 1 in both holes.

 

+1 - Motor Oil has an additive package designed to deal with the byproducts of the combustion process. You don't need this in the gear box.

Gear Oil is formulated with an additive package to deal with shearing which occurs in the tranny.

While the MoCo for several years was recommending Motor oil in "all the holes", that is no longer the case. Their recommended choice for the Primary/Tranny is now Formula+, which is a Gear Oil.

My choice is Mobil-1 15w-50 in the motor, and Mobil-1 75-90 Gear Oil in the primary/tranny.

 

Thanks guys that's kinda what I thought but I figured I'd ask around...



that's cool I'll answer it.. 2 reasons.. one is because when I pulled the derby cover I was alone and the bike was on its stand and some leaked out..

and second being that the bike as 26,000 miles on it and figured its about time.. because I don't think the previous owner ever did.. and I would rather be safe than sorry..

 

I'm currently using Amsoil 20W-50 for both the engine and tranny, but I think I'm going to look for 75W-90 for the next change.

 

With you doing that does it seem to run differently?