I was told not to use 10w-40 in my Raptor. Here is the reason I was given:

Multi-viscosity oils contain a large amount of polymers in it. This is what gives it the variable range of viscosities (10-40). 10w-40 and 5w-30 contain the most amount of polymers of any motor oil. As oil gets used in your engine, these polymers decompose, and your oil eventually needs changed because of this. The problem with 10w-40 (and 5w-30), is that because of the large amounts of polymers, it leaves more of a residue in your engine, which, over time, could cause problems.

I dunno how much truth there is in this, but this is what I was told...

 

That's interesting. When I purchased my Raptor I asked my dealer if Amoco 10w-40 oil was OK to use and they said yes. Chet read this about The Great Oil Debate

 

From the oil page I posted ealier:
Multi viscosity oils work like this: Polymers are added to a light base
(5W, 10W, 20W), which prevent the oil from thinning as much as it warms
up. At cold temperatures the polymers are coiled up and allow the oil to
flow as their low numbers indicate. As the oil warms up the polymers begin
to unwind into long chains that prevent the oil from thinning as much as
it normally would. The result is that at 100 degrees C the oil has thinned
only as much as the higher viscosity number indicates. Another way of
looking at multi-vis oils is to think of a 20W-50 as a 20 weight oil that
will not thin more than a 50 weight would when hot.
Multi viscosity oils are one of the great improvements in oils, but they
should be chosen wisely. Always use a multi grade with the narrowest span
of viscosity that is appropriate for the temperatures you are going to
encounter. In the winter base your decision on the lowest temperature you
will encounter, in the summer, the highest temperature you expect. The
polymers can shear and burn forming deposits that can cause ring sticking
and other problems. 10W-40 and 5W-30 require a lot of polymers (synthetics
excluded) to achieve that range. This has caused problems in diesel
engines, but fewer polymers are better for all engines. The wide viscosity
range oils, in general, are more prone to viscosity and thermal breakdown
due to the high polymer content. It is the oil that lubricates, not the
additives. Oils that can do their job with the fewest additives are thebest.
Very few manufactures recommend 10W-40 any more, and some threaten to void
warranties if it is used.

I don't use 10w-40 in my cars, motorcycle, or ATV. And, I try to avoid asking dealers anything other than, is my part in.

 

I don't have my owners manuals from my Recon and 300 4 Trax in front of me but I believe that is what Honda recommends 10w-40.
Chet

 

I have only one piece of advice when it comes to oil. Use oil certified for use in motorcycles or ATVs only, especially specific for you application. I only run the Yamalube 20-40 in my Raptor. I build a lot of ATV motors within a year, and you can buy a crank now, or you can buy a crank later it is totally up to you. Some guys that are running any old 10-30 such as Quaker, Valvoline, Penzoil or any other automotive oil will definately see increased wear and tear over the life of their machine. I see it all the time. I just finished a Suzuki LTF 250 that was run with any old 10-30 and the top end was fried. The cam was killed not to mention the rocker arms finished. It was all due to overheating and using cheap oil. I was once told this many years ago buy a 20 year Yamaha mechanic who taught me how to rebuild these engines, i did'nt believe him either. My old Warrior which was a 1997 blew the bottom bearing all because i was running Quaker 10-30. I have seen it so many times over this past year, and have passed along his knowledge. When you have to rebuild a Raptor motor, you will pay somewhere in the $500-1300 CDN range(depending on parts), and you will wish you spent the extra $2-5 per oil change. If anyone tells you it is okay to run automotive oil in a Raptor engine, they are not doing you any favors. Remember you can buy a crank now, or a crank later !

 

I run Amsoil in everything I own. In my LT I used to run their two stroke oil at 67 to 1. Engine was great. My 400EX has run flawlessly for 3 years. My CBR totally quieted down when I switched from the breakin oil to Amsoil. My YZ 426 (known weak clutch for that year) ran perfect. My raptor runs like a dream and I also ride it very hard.

Every machine that runs it, never has engine problems. In fact, it makes them run better. Especially the small import cars like Hondas that get their power at the top.

Can't say enough about it. Never let me down.

RM