What kind of oil can i use?

Yamalube 20w40 4-stroke engine oil - I have a sh!tload of this stuff. Will this work? I know its Yamaha but what are the downsides?

I suppose a yamaha Raptor oil filter wont fit.. what oil filter can i get for a 1998 prarie 400

 

I use a Fram 6017a.Thats for my 650 and it also works for a Grizz and a Kodiak.Go to Walmart and look.They have a book to look them up.Some guys say only use the OEM filters.Myself and everyone else that rides with me have been using the Fram and NO ONE has had an engine issue.
As far as Oil that will probably get a million opinions......I personally use Castrol Full Synthetic 5w-50.That covers the whole temp range.With your lower number being 20w I would not use that in colder climates.It will not flow well at low temps.In the summer it should be ok.
I bought an oil filter for a buddies P400 a while back and I am almost sure it called for the 6017a just like my 650 did.
02 650 camo

 

My dad uses Havoline 10W30 in his Twin Peaks, which is basically a prarie.

 

The Yamalube 20w40 4-stroke engine oil will work fine (it's not made by Yamaha, it just has their name on it) Do not just car oil, it has friction inhibitors add and will damage your trans if it shares the same oil as the engine (Don’t know much about belt drives). Just use your favorite 4 stroke motorcycle oil. And everyone has an opinion as to what is best.

 

Auto oil is fine for a Prairie,they do not have an internal clutch.
02 650 camo

 

I used Amsoil Formula 4-Stroke Synthetic 0W-40 Motor Oil.

 

ditto archangel....You might want to go to Amsoil's site and find out about synthetic oil. I use it in all my engines and trannies.

 

I've started using the Amsoil Synthetic Tractor Hydraulic/Transmission Oil
SAE 5W-30 (ATH) in my rear diffs as well.