Since new mine has used about 1/4 of a gallon of coolant, and I suspect it has been lost through the drain tube on the reservoir bottle during trail runs. Mine has had a sticking radiator cap, where I open the hood and the upper radiator hose is collapsed. Releasing the cap vents the system and all is ok. In recent months that has stopped and at one point the coolant was at the "min" mark. I have a gallon of the factory coolant, mixed a 50/50 spritz and put just a bit in there to get the level in the reservoir just a bit below the "max" mark when fully warmed up. I have read that some guys had head gaskets replaced for this issue, time will tell I guess. I'm at 48k miles now and this doesn't seem like a lot of coolant loss to me. No running problems that would indicate a bad head gasket.
'09 JKRU. 4" Teraflex long arm, Teraflex R44 housing, Teraflex / Fox Resis, Poly Performance skids, Nemesis Billy Rockers, Nemesis flares, 37" ATZ P3s on 17" 5x5.5" Trailready HDs, Spyntec hubs, Teraflex BBK, Mopar BBK master/booster, Superior front & Alloy USA rear axle shafts, CTMs, Reids, Synergy drag link & tie rod, WTOR hydro-boosted steering, 5.38s, TF Dual Rate front bar, TF bumpers, Warn Powerplant, Tom Woods shafts, AA xfer case cable, Kilby canister relo, RH4x4 cage.