the thicker the fluid the more even the power is going to be distributed between the right and left. In a truggy you use a thicker fluid in front because the front tires tend to unload alot easier but you dont want to go too thick otherwise you loose steering. You still want the steering to pull you around tight corners and not let the rear push you around corners. If you were to use a thicker oil in the rear and thinner in front the rear will tend to push into corners which you dont want for racing. Now this is for truggies and buggies. Monster trucks on the other hand is the opposite. You want thick fluid in the rear and thinner in front. Monster trucks already have a hard enough time turning but you dont need to make such tight turns that truggies would have to make. You can put 60wt or even thicker and get great traction but still not have near the stress on the drivetrain as a spool would have. Go as thick as you want as long as the tires work seperately from each other.