Originally posted by pym-ftw
Gasoline fire burns around 1k F
Diesel burns at about 300F2500c is around 4500F
Your argument is invalid
If Marvel comic writers thought the flame from gasoline tanks and vehicle explosions and the like made for low temperature fires you'd still have the concussive force of those things to deal with, and Petey's been knocked out by things as low level as Sebastian Shaw slamming him into the wooden walls of the Hellfire Club.
Moreover, such is hardly the only method Batman has for producing heat. More than that, there's no reason the process has to be hot then cold. The reverse should work just as well and Batman actually seems to carry a pen laser around with him as fairly standard equipment as well. You can see it at work in the aforementioned Hush skirmish, and you can also see it in Supergirl #5.
As it is Marvel comic writers treat gasoline fire as a very hot fire indeed. In Marvel Team Up #150, for instance, it is actually hot enough for the half-powered Juggernaut to feel, even as the flame from another gasoline explosion, a tanker truck, was enough for Cain to feel, though just barely, at FULL power, when taking on Spider-man the first time around. Even a million volts of electricity didn't seem enough for the author to say Juggernaut was registering before that point.
Again, though, it's the combination of hot and cold that must be stressed. Neither alone is expected to do the job -- and neither needs to.