Has anybody tried either of the Amsoil shock oils either in a sled or a motorcycle application? I'm wondering which is better for aggressive trail riding in a snowmobile application; light or heavy fluid. I haven't used them yet and would like to try them out to see if there is any difference between the weights or any difference between the Amsoil and other fluids. Thanks.

Give you an example

The stock oil is #4 weight in the 440 rev.
Changing the oil weight by increasing the number does a few things to calibration.
The low speed valve stack is usually affected the most and can be felt the best by seat-of-the-pants.
Depending on the weight number you will find that with a higher number the nice plush ride that you had will not be there any more. The oil has to be forced harder thru the valves to pass, so it would require you hit bumps harder to achieve that plush ride you once had. Drivers will come back and mention "spooky" because the sled will skip along the top of shallow bumps and the rear of the sled may even feel like it's swapping side-to-side.
The rebound will be slowed down now too. The suspension will be slower to cycle back to original position. If you were to put a very high # of oil in the shocks, depending on the frequency of cycles, the shocks may start to compact and you lose suspension travel. When the rebound is too slow you tend to get arm pump.
The high-speed valve stack action will slow down also and the results will you being able to pound in deep bumps pretty good.

Bomber recommends to use a #4 oil and if needed at the most a #5 oil because of calibration. I talk with Sebastian [Bomber shock guy] about the oils and he recommends to stay away from bike oils because most will not handle the change of operating temperature to cold in a more aggressive driving environments.
He admit there are some good bike shock oils, but very few.

I think regardless of brand, the capacity of the shock oil inside is determined by the patience of the tuner with their task of removing as much air as possible.

You can use amsoil till the cows come home, but if it is the wrong viscosity and is not designed for such temperature variance, then you wasted your time and money.

http://www.amsoil.com/products/stl.html

Make of it what you want. Looking at the numbers should tell you a little bit.

Thanks. I have the spec info but was unsure which would be better for the sleds in the cold temps. I don't have any experience with the shock oil and didn't know the specs related to real world use. Looking at those specs does the heavy oil look too heavy for sleds?

The light is actually pretty light fluid, and the medium is fairly heavy as far as shock fluids go. If I was you, I would work with the Light first. However, you do have the option of blending of them and your viscosity would then be a average of the 2.

Example:
Light
Kinematic of 4.33 @ 100 deg C
Medium
Kinematic of 7.33 @ 100 deg C
Blend
Kinematic of 5.85 @100 deg C

Talking about comparing shock fluid viscosities is kind of worthless without these specs. Everybody's specs differ and in my opinion nobody should be referring to any hydrualic fluids as "weights". Either the kinematic viscosity numbers or the SUS ratings are more referenceable. Personally, I just look at the Kinematic viscosity values. Companies use the "wt" designations though because it is easier for the average guy to grasp.

One thing on fluid fade. The spec that relates to that is the VI (viscosity index). The higher the VI the more temp stable the fluid is. 200 VI is only average. 300+ is good. But regardless you WILL have fluid fade involved. This is not a result of breakdown, it's simply the viscosity change is unavoidable. I don't care what you have for fluid in your sled shocks...it WILL fade as it heats. You can't stop that from happening you can only hope to minimize it in our enviroments. When you take a shock with a ambient temp of say Zero Deg and through normal use heat it to an operating temp of 100 deg that fluid is going to change viscosity, period. At some point that viscosity is going to begin to stabilize and as your shock heats further the amount of fade will be a lot less. In other words your biggest change in viscosity is going to be from ambient to operating temp.

Thanks Springer. It sounds like that was the info I was looking for. Do you know of another brand that has better "specs" than the Amsoil? The Amsoil VI appears to be only average.

http://www.maximausa.com/products/suspension/shockfluid.asp

These are decent fluids but I would say you would be needing to change them more often then you may think.

So how close is the Amsoil lightweight fluid to the recommended Ski Doo brand?

Thanks for all the good input.

The Amsoil is also ment for sled suspension , and light is rated at 5 to 0 or #1 by race tech maxima. It has a well below zero rating. Also on back says is replacement for rydefx oils

I have been messing around with different brands of oil this year and over the weekend I went upstate ny and it was very cold in the am 15 plus below zero. Before I left I decided to take all the brands of oil I had. Amsoil light 3 different weights of redline and a qt of maxim 3wt . the maxim is not synthetic, butthe rest were. So I left them outside in the bed of my pickup and at 8am I went out and shook each bottle . All bottles except the maxim are see thru. The amsoil and maxim were still in a liquid state and were slightly stiffer due to the cold, but the redline was in a solid state! Not frozen, but it acted like it! I had on pt of like water (weight) and 2.5 weight. The lighter weight was stiffer than the 2.5wt. I had a shock to test with the 2.5 redline . I didnt try it. Changed to amsoil today. Hey dynamo- joe what oil do you use and what does sabastian at bomber say to use?

Told ya !! Amsoil won't fail you !! I use the stuff in everything I own truck , snowmobile injector and chaincase awesome stuff. I use it in my crf 450 , they even have a light oil for winter time so it is easy to start my bike when I go out on the ice .