I’m watching ABC news coverage of the LA Fires.
They reported from a street where drivers were stuck in traffic, fleeing the advancing fire. Drivers had to abandoned the cars and run for their lives.
The cars were badly charred and burned.
No indication that the gas tank exploded?
Wouldn’t explosions be expected as the tank temperatures rapidly increased?
I know this from my tenure – decades ago – as a volunteer firefighter. I saw lots of car fires, but none exploded:
That is very interesting. Thanks.
I was always warned to watch my torch when heating rusty bolts (helps remove with a wrench) under a car. Didn’t want to accidentally set off the gas tank.
I’d still watch where my torch is aimed. But it’s reassuring gas tanks aren’t bombs.
‘Exploding’ cars are a Hollywood trope that basically doesn’t exist in real life. I’ve seen cars violently burning from an engine fire, and if it propagates to the gas tank you can get a big ‘whoosh’ from volatized gas suddenly combusting but the car explosions you see in movies with the hero being flung backwards are nonsense, notwithstanding that any blast wave energetic enough to propel someone many feet backwards is going to turn their insides into jelly.
Stranger
Some might be diesels.
Also … vented gas caps 
While you can find diesel passenger cars in the United States if you look hard enough, they are far less common than in Europe. Diesel full sized trucks and utility vehicles are more likely but most gas stations only have a couple of diesel pumps unless they serve fleet vehicles or tractor-trailers.
Stranger
I would guess most gas tanks today are made of plastic. The plastic will start to melt and the gas comes out. The fire may get hotter/bigger for a short time as the gas pours on the ground and gets burned.
Now with older cars, much older cars, with metal gas tanks if the gas inside the tank gets hot enough to ignite it may explode (probably not blowing the whole car apart) as the tank’s vent system us overwhelmed.
Nope. The explosively stoichiometric mixture is a couple of teaspoons of fuel in a 20 gallon tank. Any plausible amount of fuel in the tank means the airspace above, “ullage”, is vastly too rich to ignite, much less explode.
As it gets hot the fuel & air will escape out the vents, be diluted by the larger atmosphere and eventuly ignite if dilute enough. Yhereby fuelling the larger conflagration.
Bottom line: the fuel tank is an accelerant and a sustainer for a vehicle fire; it’s not a bomb. Except on TV shows.
Well these fires are pretty close to Hollywood though.
An explosion from liquid in a closed container with no escape is a BLEVE, boiling liquid expanding vapour explosion. It doesn’t involve chemical reactions. But you need a proper pressure vessel to hold the liquid within which you boil the liquid. Otherwise you won’t get much pressure buildup before it just goes pop. Which is what will happen with a car fuel tank.
A bleve is an extremely dangerous event. In times of old think steam boiler explosions, either stationary engines or steam locomotives. In the modern world there have been breves involving lpg tankers. The destructive power comes from the boiling liquid transiting into gas. A large fireball just adds to the drama. It doesn’t add much to the explosion. Just water is just as, if not more, destructive. No combustion needed.
The energy that a large vessel full of water can contain when under pressure is extraordinary. The temperature doesn’t rise much as you continue to pump energy in. The latent heat of evaporation of water is huge, and the water ceases to be a simple liquid. All that energy gets turned into the kinetic energy of the blast if the vessel ruptures.
This is a key reason why your BBQ gas cylinder has a safety valve. A cylinder caught in a house fire or wild fire must safely vent. You get an impressive jet of flame shooting upwards until the cylinder empties. But that is much preferred to a bleve that can level the house. Sometimes the safety valve isn’t enough and a cylinder weakened by the fire may eventually rupture anyway. Albeit at a lower pressure than would have occurred with no safety valve and thus less destructive. Bad enough to kill people however.
The effort Hollywood goes to make a car explosion is ridiculous. Plastic bottles of petrol jammed into corners of the car, all with detonators to rupture the containers and spray the contents around at the right moment, along with actual explosives to make the bang. Cars just don’t want to do this in real life.
Thank you for the detailed explanation.
A intense fuel fire could burn down a garage. But thankfully it’s not likely to explode.
Ref @Francis_Vaughan this is a decent explanation & sample:
Pilot; are you flying a stealth plane, you damn ninja!
Blue Rhino (propane filling) plant explosion in FL 11 years ago. I’ve keyed it up to where a single standard 4 gal backyard BBQ propane take cooks off from out of a tractor trailer here
I was living in this city, but not nearby, when this fun event cooked off:
Off topic: what area was that?
Most notable expamples were Sunset Boulevard and Palisades Drive. People ditch their cars and locked them. The firefighters had to go in with bulldozers to clear safe passage for their trucks.
An unintentionally humorous part of an otherwise dark moment is where a tv reporter was talking to a volunteer that was trying to move cars and didn’t realize it was the actor Steve Guttenberg.
Apparently, the only real Hollywood car “explosion” was in American Graffiti when Harrison Ford up-ends his jalopy and it burns but don’t go BOOM.
Having been the witness to dozens and dozens of car fires over the last 43 years as a LEO I’ll tell you the thing that goes Ka-f*cking-boom is the tires. Sometimes it’s a disappointment and sometimes it is spectacular! Semi-truck tires burning you want to be very clear of.
Funny you mention that; I saw a YouTube clip the other day where a car carrier had a tire blow while in transit and it completely creamed the entire driver side of one of the cars being transported.
I don’t get how they put tires on rims by spraying some flammable stuff on the tire and touching it off — FOOM! and it’s seated.