I am just getting ready to change my oil on my kfx400. I went to get some oil and I was told to use 20w 50 instead of the recommended 10w 40 since it's getting ready to be summer. Should I use it or stick with the 10w-40? All help is appreciated. (I am heading to Little Sahara sand dunes next weekend if that makes a difference)

 

I wouldnt see any benefit to using an oil weight not reccomended by the owners manual. If you think youd like more protection, than whats reccomended, try a synthetic 10w 40.

 

No reason to use a 20w-50 in a watercooled bike unless it needs rings and burns thinner oil.

 

10w40 cools faster that 20w50 too

 

I wouldn't use 20w50 in a KFX. I think it's a bit heavy for that engine. Thicker is not always better, that's an "old racers" tale for the most part.

I use Amsoil 10w40 and have had no problems this summer. And last week I raced a Hare Scramble and it was over 90 degrees.

If anything I'd go with a 15w40 over a 20w50.

 

My ds Manual recomends 10w40. I use bel ray thumper 20 w50 semi senthetic, and it lowered my operating temps atleast 5 degrees. It's good stuff. I use it year round, even when it's 5 degrees above zero. Thin enough for winter, unbeatable for summer.

 

The difference between 10W-40 and a 20W 50 as far as operating temperature recomendations are negligable during the summer. The thing you are benefiting from with a 20W 50 is less viscosity breakdown. The thicker the oil, the more you can run the **** out of the engine and not experience oil degredation. And lets face it, we all run the **** out of our quads, don't we? [img]i/expressions/face-icon-small-wink.gif[/img]

 

I dont know about that. Thicker oil absorbs more heat, that is a fact. So what your saying is the only difference between 10w40, and 20w50, is 10w40 will need to be changed sooner than 20w50???

 

No not at all. And you are definately right about heat absorbtion. Good call. That is more what I was getting at. Since it can absorb more heat, it will not lose its ability to lubricate efficiently as quickly.

 

The thing about the 20w50 is that while you are sitting at idle your engine will retain more heat compared to 10w40.

If you race MX where your RPMs are high all the time you will benefit from 20w50. If you are in the traills putting at low RPMs the 10w40 will actually stay cooler.

And as far as viscosity goes, if you use a good synthetic thermal breakdown should not be an issue with 10w40 at all. In the old days with the old oils it made a bigger difference, you needed 20w50 if you were going to pound on your machine. Today's synthetics are so good, breakdown should not be an issue.

On the flip side, it takes your engine more energy to push through a heavier oil. Heavier oils can actually rob power in some instances, especially at cold temperatures. However again the new 20w50s aren't likely to make a difference that one will notice.

It's really a matter of what you have been told over the years it seems. But if you notice the thicker oils are getting fewer and farther between for modern engines. The tolerances are getting so small that thicker oils can't even push through the systems. Ford is using 5w20 in everything now and they are working with ZERO weight oils now, that stuff is like pure water.