I posted a thread about a year ago concerning this, but came to realize these engines just make noise. Type in a search for "knock" and you come up with a slew of threads. But I noticed mine only did it after warming up. So I figured the oil might have something to do with it. When the engine is warm, the Polaris 0W-40 oil runs off the dip-stick like water. I don't live in an area where it gets too cold, so the 0W-40 really isn't necessary. During this last oil change, I switched to Castrol Syntec 5W-50. The slightly heavier oil quieted things down noticably.

 

Any oil at operating temp is going to look like water. The motor was designed for a 40wt oil and you are using a 50wt. Probably won't hurt anything, but you may get less flow, and probably slightly less horsepower.

 

I would be careful ... they have had the 500HO engine for awhile and i'm sure the 0W-40 oil was designed for that engine.

 

A heavier oil may mask the sound because it it thicker, it has more sound damping, but it may be actually lubricating less. Just because it makes less noise doesn't mean it is working better for your engine. The only way to tell which oil is working better is to do a UOA (used oil analysis) by sending a sample into a lab for testing.

 

When I put my Hot cam in the other day it said not to use synthetic oil to break it in. So I used a good grade of atv oil that was 10w-40 to break it in. I notice when I put it in the engine was quieter and after an hour of break in I dumped it out put the synthetic 0w-40 oil back in and the engine noise was a little louder.

 

Just face it, these machines just make noise and to switch oil isn't something I would recommend doing. lube specs are researched from the factory and if they recommend 0w40 then I am gonna use 0w40

 

just like jimmysp70003, we had a scrammy with a web camshaft and we were told not to run the syn. at all, not the case with yours jim i know. but we did run sae 30w in cold weather, and sae 50w in hot weather. the motor was quieter with these oils until they broke down some. after taking cam out we went back to syn 0-40. with your warmer climate you probably won't have problems, but just keep an eye on things. oh yeah, with the straight weights, we did change the oil alot. usually after every race and about 10hrs on trails.

 

With a straight weight oil you are losing your cold start protection. It will take longer for the thicker oil to flow until it gets to temperature.

 

You could put some fine sawdust in with the oil to quiet it and then trade it(Just kidding). I run Synthetic 5W-50 in my 99 SP 335 for the last 2000 miles with no proublems. Although I try not to use below -15 degrees celcius.

 

i thought my engine was knockin one time and it was my belt fallin apart lol