Can petrol evaporate?

Serious qu. I have spent £40 maybe £50 on petrol. Dad left the non-jeep with abut 1/2 a tank and i took it to my show so say a 45mile round trip and i had to put £10 in about 10miles from home and when i opened it a big huge woosh came out. Not drove it again since, but got in to take my cousin home and it was red light after about a mile.

anyway, put £30 or 40 in my KA and i have literally done about 40 miles in total and its about to go red again.

Whats going on?

It was probably air being sucked in , the tank has a breather up the top somewhere ususally , possibly in the cap so as the petrol goes down it creates a vacuum effect and when you take the cap off the air is being sucked in if it is not breathing properly

There is air pressure in the tank and without some way for the petrol to evaporate (normal conditions = no), so that can explain the whoosh (Drat your quick fingers Dave). The KA issue would be more concerning. Perhaps a bad pump at the station... or a leak somewhere (you did put the cap on right?).

yeah i always put it on and make sure it clicks a few times. Its just been so hot i thought it was maybe gushing out when i open it lol

The price is ricic at the moment so that doesnt help but i have never used so much money on petrol in two weeks and not actually gone anywhere, normally i drive for hours.

Hayley wrote:yeah i always put it on and make sure it clicks a few times. Its just been so hot i thought it was maybe gushing out when i open it lol

Nope. Sounds like something more than heat. Hopefully just a bad pump at that station.

thats a con then! wouldn't put it past them lol

air con on all the time? it zapps around 8-10 mpg off mine when i have it on.
you shouldnt be evaporating that much although some does go by evaporation but my 200 lasted 2 years in the guarage before it lost about 3 litres.
id suspect that you either have a leak or its running very rich and you have a sensor problem. is there alot of soot in your exhaust pipe? a sure sign of running too rich.

Ka doesnt have AC, or soot as far as i know

if you fill up when its colder, like it is mostly in britain, the petrol os more dense, technically you get more petrol for your money, and more miles per tank.

also, petrol engines run a lot more efficiently with colder, dense air. theres not much of it about at the minute, so engines will run less efficiently and less economically.

also, petrol is highly volatile, much like alcohol it does evaporate at relatively low temperatures. possibility that it it's still in your tank, just in a vapourous form as opposed to liquid (and as your level sensor in the tank only measures liquid, it wont measure everything thats in the tank) see what the gauge reads in the morning, after a long cool night, as opposed to what it reads now after a hot day.

*remove sciency hat, put on mechanics hat*

any smell of fuel near the car? old first generation Ka's have a pressed steel tank, the new ones have a moulded platic tank. both have plastic fuel lines, and off the top of my head, the only real leak risk on an onlder one is the fuel filter near the tank, only made of thin aluminium and rot if not changed every couple of years. relativly cheap and easy to replace

No smell no. Very interesting about the temps though! It's a late 05 ka so

My dads a mechanic, he said to get your filters checked too, if they haven't been changed in a while it can eat through fuel quite quickly!