What are your thoughts on useing 5w40 oil for 100 degree plus temperatures in the summer desert heat. I bought a new 2005 sportsman 500 which the owners manual states you must use 0w40 no matter how hot or cold the temperature conditions are outside! I have never seen a manufacturer before that didn't reccommend matching the oil weight with the anticipated upcoming weather conditions. My concern is will this engine pump zero weight oil at idling conditions in this severe heat? I don't see how they expect the same weight oil to perform equally well at 110 degrees above zero as at 40 degrees below zero? Polaris says warranty is void if you use anything else. I have a 2002 yamaha grizzly with over 12,000 miles on it and always run heavier oil in the summer time. What gives here???

 

The 0w40 oil will handle the full temperature range you operate in. The quad engines normal operating temp is well above 100 degrees so the temps you speak of don't affect your quad as much as they do you physically. 0w40 will give the same protection as 5w40 in hot temps, the 40 being the key in both.....

 

I have been using 5W50 for the last 2000 miles with no proublems

 

The whole idea of multi range oil's is that they cover a wide range of temps. Running 5 w40 compared to 0w40 is going to be no different in the heat as the max temp viscosity is going to be 40 for both oils. The only difference here is going to be when its real cold out...like below freezing. A 0 w40 oil will turn over easier then a 5w 40 oil .

 

Viscosity refers to how "thick" or "thin" a liquid is, or how easily it pours. Viscosity also is commonly referred to as "weight," as in a light-weight or heavy-weight oil. Viscosity is really a bit more complicated than simply "thick" or "thin" or "weight," but the Society of Automotive Engineers has organized viscosity ratings in a series of numbers that is easy to understand.

Oil viscosity is affected by temperature. A heavy oil that stays relatively thick at high temperatures would have a high-viscosity rating of 30, 40, or 50. A thin oil that flows freely at low temperatures would have a lower number. Because temperature affects how well any liquid flows, motor oil viscosity is rated at both high and low temperatures. The lower viscosity numbers of 20, 15, 10, and 5 are accompanied by a "W" for "winter." Some motor oils today have a single viscosity rating, such as SAE 30, but many are designed to work in a wide range of temperatures. Such oils have a dual viscosity rating, such as 5W-20 or 15W-30.
When an oil is cold its viscosity increases, and it does not flow easily. If you use high-viscosity oil in low-temperature weather, heavily loaded engine parts will not receive oil until the engine warms and the oil thins. Hot oil, on the other hand, is thin and flows easily. Low-viscosity oil in an engine running at very high temperature may break down and allow moving parts to rub against each other. This can cause rapid engine wear and possible damage.

VISCOSITY COMPARISON CHART

Material - Viscosity (centipoises)
Water @ 70o F - 1-5
Blood or Kerosene - 10
Anti-Freeze or Ethylene Glycol - 15
Motor Oil SAE 10 or Corn Syrup - 50-100
Motor Oil SAE 30 or Maple Syrup - 150-200
Motor Oil SAE 40 or Castor Oil - 250-500
Motor Oil SAE 60 or Glycerin - 1,000-2,000
Karo Corn Syrup or Honey - 2,000-3,000
Blackstrap Molasses - 5,000-10,000
Hershey Chocolate Syrup - 10,000-25,000
Heinz Ketchup or French’s Mustard* - 50,000-70,000
Tomato Paste or Peanut Butter - 150,000-200,000
Crisco Shortening or Lard - 1,000,000-2,000,000
Caulking Compound - 5,000,000-10,000,000
Window Putty - 100,000,000

Hope this helps. There is supposed to be space between the Material listed and the Viscosity value but it gets taken out when posted, sorry.

 

Thanks for all your help folks. The posts were very informative. I guess my post needs more clarification. It is the first number I was concerned with. It's the 0 in 0w40 I was worried about in severe heat. I felt the 5 in 5w40 would be a better number at temperatures pegging 110 degrees.
Thanks, Jerry