And, it will be less weight per gallon than water, RV anti-freeze, or WW fluid.
I too would be afraid of the rubber breaking down from the oil.
Water is 8.34 pounds per gallon.
Mineral oil is 7 pounds per gallon....But hey, its free!
Yeah I know. Real rimguard weights around 12lbs/gallon; 30% above what water/calcium weights (as "advertised" though)
I already have a 2¼"x14"x11" metal plate (100±lbs) bolted on the back of my old LT1100(±?±?) 11hp 6speed Craftsman II. But, even though it is effective, I don't mindfully truly enjoy having this weight (+my own 170lbs) supported by its aluminium housing-trans. It is set on Duro Mud ATV tires 22x11-8 tires (instead of the original Turf tires 18"x10"x8" it had). I have not yet found a way to calculate what they can hold (If anyone has found a quick math formula for this, please tell me lol;) But my guess is they can hold around 6 to 7 gallons per tires.
I yet have to make some good pics of my "now" range of 4 "given/free" lawn/garden tractors (one working) and explain their use (as each their turn comes into work lol ;) (the 4th one was even delivered free yesterday. Best of all, I don't even search for them except for the one that's working everyday; such as hauling/delivering door-to-door flyers once every week)