So many weights and don't know which one to buy. Why so many weights and what is the difference?
Rustler VXL Emaxx 3906 E-Revo Dewalt
The thicker the oil, the more dampening you get (slower the piston travels in the body).
If the oil was like water, the travel would not be dampened at all, and the truck would just bounce like crazy, since there would be nothing to slow the bounce.
If the oil was like thick grease, the travel would pretty much not exist, since it would take a ton of pressure and a ton of time to push the piston through the oil.
You have to understand that shock oil is there to dampen the suspension movement, to set the speed at which the shock compresses and then rebounds.
Project: BL Revo Race Quad & BL G-Maxx G3R CF Revo
Depending on what you want to do with your truck, you'll need different weights of shock oil. If you jump a lot or race, you probably want to go thicker...like a 60 or 70 weight in front and back. If you run on flat ground or pavement a lot, the stock (40wt, I think) shock oil is fine. Like REVO said...the pistons have different sizes and numbers of holes in them to let more or less shock oil pass through them...so they're just another way to change your shock compression.
I'm going to be racing my E-Revo, so I put 70 wt shock oil and #3 pistons all the way around (to make it stiffer for the jumps).