I've got a methanol/water mix in my tires, it came that way from the dealer and was inexpensive. I would prefer to have rimguard however as I believe it is heavier than methanol and more environmentally friendly in the event of a leak.
As far as weight per volume, Rimguard is heavier. Rimguard is also more expensive. I have read (on TBN, no personal experience) that Rimguard can cause tire slippage on the rim, so you'll want tubes in those tires.
Methanol...well, I doubt you'd use methanol. It would be a product such as winterized windshield washer fluid with a small percentage of methanol for lowering the freeze point. There have been folks stating windshield washer fluid containing methanol is flammable. Guess it is, but I've never heard or read of a tractor catching fire due to it's tire ballast.
Bottomline is you'll get more ballast (weight) from Rimguard, but you'll pay for that extra weight per volume.
It cost me 71.55 to fill both tires on mine with rimguard. But with my pond, and flower garden, I wanted to stay 'non-toxic'(just in case).
I'm using turfs on mine, so far no slippage on the rims.
I had washer fluid in my old Cub Cadet for 14 years, never had a leak til 2 weeks before I bought the Massey.
Edit: I should add that the charge for the Rimguard was 2.50 per gallon@17 gallons, plus 26.50 labor, plus tax.
If you go with Rimguard, and no tubes......be sure to replace the valve stems with metal ones. The rimguard has been eating the glue in the rubber stems.( according to Rimguard Co.)
Mines filled with water/methinal,and it was methinal,saw the barrel it came in,stinky stuff,,its been in for couple years now.They got about a 30 percent methinal to water ratio[more or less],should be good to about 0 f,at least? No tubes,run air pressure on the low side,have done a good bit of spinning in past couple of years,no slippage that I can tell anyways
My Tc34 rear tires were filled with a mix of methanol (from a barrel that was labeled methanol) and water with a ratio of I believe 1 gallon of methanol to 3 gallons of water. Running tubeless tire and have never noticed any slippage of the rim.
rimguard is about 25% heavier than water. I think it's 11lb/gal.
Regardless of what you choose, it's fairly easy to fill your own tires and that can save some $$.
I have tubes and rimguard. I bought 100 gal at $3.00 gal a few years back. Brought it home and put in the tires. Took about 2 hours. I think I got about 45 gal/tire in mine.
I put Rimguard in my rears this past spring. If I remember correctly, I paid just under $5 a gallon to have them come out and install it. I used the nearest dealer, but they still had to travel about 140 miles round trip, so I thought the cost was fair.
I have been very happy with it. I added over 1000 pounds, and it made a world of difference, obviously. I do not have tubes, and so far have not experienced any slippage in about 70 hours of mowing and loader work. The dealer did change out my stems.
I opted for the RV anti-freeze. I thought about the windshield washer fluid, but decided against it as the methanol is poison if ingested(so dont drink it!) and the air in the tire will have methanol vapor in it which is flameable or so I have read. I have no first hand experience with the methanol mixes. But it is cheaper than the RV antifreeze or the Rimguard. I could not find a rimguard dealer or source around here. So I put the RV anti-freeze in myself. actually almost a fun job. The RV antifreeze (polyethelene glycol) is supposed to be safe if ingested, (I did not drink any but it looked yummy!) and not supposed to rust your rims. ( I guess time will tell on that one). Of course like everyone says. your tractor is much more stable on hills, and will pull/push more. I guess Tract-ion is what Tract-ors are all about!