If you were to fill a junk car or a semi full with an even mixture of gasoline and thermite and set it on fire would it melt the car down to nothing? What would happen?
((Assuming that the vehicle is filled to the brim with the even mixture of gasoline and thermite))
The gasoline would ignite, and burn until the thermite got hot enough to ignite, at which point the car would melt into a bright, glowing mass.
Why bother with the gasoline?
You get a long lecture from Smokey The Bear.
I don’t know whether a gasoline fire would get hot enough to ignite the thermite. Wikipedia says “These temperatures cannot be reached with conventional black powder fuses, nitrocellulose rods, detonators, pyrotechnic initiators, or other common igniting substances.”
I’m not sure gasoline would burn hot enough to ignite the thermite. If it did then yes, the car would wind up as a puddle of liquid steel. It all depend on which flavor of thermite you use. Duct tape a chunk of magnesium to the thermite, let us know what happens …
Use a road flare to ignite the thermite and skip the gasoline entirely.
If the car has any alloy wheels or engine components, the gasoline fire may well set fire to the magnesium/aluminium alloy and that then sets fire to the thermite.
A sparkler does a fine job igniting a flower pot full of thermite… Or so I’ve been led to believe. 
The gasoline is a waste and totally unnecessary.
Unnecessary, sure. But a waste? It makes the fire bigger, if not brighter.
Waste not, want not. George H Goble was ahead of his time when he cooked his hamburgers on the charcoal grill using only a smouldering cigarette and LOX. He was awarded the 1996 Ig Nobel Prize (Chemistry) for this.
Assuming something gets hot enough to ignite the thermite there might be an explosion as a result of pre-heating a large portion of it to high temperatures with gasoline. It doesn’t seem likely that the thermite will ignite with just gasoline and air to heat it though. If there was thermite in the engine compartment along with a charged battery it’s possible that a short close to the battery could ignite the thermite mixture under some ideal circumstances.
Ok, the gasoline is utterly gratuitous, but does make a pretty fireflower. Happy now? 