Picked up a 05 Sportsman 90. I bought the Polaris synthetic VS oil for the injection system.
I'm a believer in the synthetic oils... the kid keep the 90's throttle pushed to the bar most of the time. I would reather spend the money on the oil vs on parts. I have read the issues on the little bores and stuck rings or just plain wear.
I'm just curious on what oil are you running in the 50's and 90's out there?

 

Mine still has the original oil in it. I'll go to the Polaris Gold synthetic when its time to add.... If your going to switch, drain out all the old before adding the new. Its not good to mix.

 

When I looked at the dealers oil selection the two synthetic oils Polaris VS and Gold. The price was the same for the VS and the Gold. VS is for the power valve type engines... I know the little 90 does not have power valves in the engine. But I thought on it and the detergent in the VS will keep the carbon deposits from forming.... Gold does not have the same additive package. I take it either one would be just fine... Me being thirfty...get the improved additive for the same price.

 

I use Blenzoil. It is clear and does not have the odor of other oils. That plays a big part with us because if my wife or myself are behind my 7 yr old, it makes it a whole lot better ride not smelling that crap. It is pricey...but worth it.

 

I was going to use Klotz. Heard it has a great smell. Posted something here once on it (klotz) and took alot of heat for wanting to use something just because it smelt good.

 

Forget that heat....they arent the ones riding behind one of these smokers. Let them say what they will.....you cant see the smoke and hardly smell it with Blenzoil

 

Try Spectro Oils. They are well known and have been around awhile.