and dismissed it, because I couldn't immidiately locate commensurate fuel efficiency metrics; same for Abrams M1-*models, Leopard Leopard 2A-, Challenger 2-. I settled for the "diesel" link, because the informant specifically claims

...Initially refurbished and upgraded [read: "modernized" to your point] T-72B3 tanks were powered by original V-84-1 diesel engine, developing 840 hp. However later production tanks were fitted with a new V-92S2F engine, developing 1 130 hp. This tank is also fitted with new tracks....

along with munition and armor details. However, having earlier qualified optimal range (ergo max fuel capacity, ergo "curb wght"), I'm not pressed to discuss hypothetical, marginal operating efficiency or inefficiency attributable to diesel-substitute "fuel oils".

Additionally, I've come across quite a bit of criticism concerning maintenance hours, replacement parts, and the usefull life of (reported) salvaged equipment shipping to the UAF. Could this "heavy tank" publicity be concealing 5%, 10%, or 20% of late model, "modern" NATO reserve MBTs for field test? Sure: Skunk works enter all manufacturer R&D. But iduno; don't care.
cockroach alert GAO | Weapon System Sustainment

The salient point is, none of them will roll—NATO's "game change" offensive is dead, literally parked—if fuel supply to Ukraine MBT operators is restricted. Do you imagine re-fitted petrol stations across the country? IRCR-flagged liquid cargo trailers, railcars?