Experiment shows how much petrol evaporates from the fuel tank when bike’s parked in the hot sun [Video]

Petrol is an extremely volatile fuel. It evaporates quickly but have you ever wondered if fuel from your tank evaporates when you park it under the sun? Well, here is an experiment that shows if the fuel can escape the fuel tank at all.

The video by Mechanical Tech Hindi shows the experiment. In the video, they fill a measuring cup with petrol. According to the marking, there is about 910 ml of petrol in the cup. With an ambient temperature of 33 Celsius, the vlogger starts his stopwatch. After waiting for two hours, The conclusion is that the rate of evaporation of the fuel was much higher in the first hour compared to the second hour.

The timelapse video shows how the level of fuel goes down with time. After keeping the cup in open for two hours, we can see that about 560 ml of fuel is left in it. Well, any kind of volatile liquid will evaporate if left open. The vlogger does not show how much fuel would have evaporated from a fuel tank.

Experiment shows how much petrol evaporates from the fuel tank when bike’s parked in the hot sun [Video]

An experiment that uses a closed tumbler would have recreated the scenario much better instead of using an open cup. Fuel tanks of vehicles are completely sealed off and fumes do not escape the tank.

Fuel tanks used to have vents

Decades ago, fuel tanks used to have vents to ensure that the fumes do not build up inside the tank. This caused partial evaporation of the fuel. As manufacturers started using advanced technology and modern engineers, manufacturers started installing evaporative emissions recovery or evap systems for short.

With the modern system in place, the vapours that form inside the fuel tank run through a canister with charcoal. The charcoal absorbs hydrocarbons or many other systems have an overflow line that safely disposes the fuel to the ground.

On older fuel systems, the engine would draw those vapours in with a vacuum. But modern engines use engine control modules that typically control a small electric solenoid that opens and allows the engine to draw these vapours into the engine and burn them.

So if you park your vehicle in the sun for extended periods, do not worry about losing fuel. There will be a negligible amount that will evaporate, if at all.

However, you should not park your vehicle for too long with fuel in it. If you plan to park your petrol vehicle for a few months, be advised that the petrol does have a shelf life. After the petrol comes in contact with air, the shelf life is about 6 months. There are additives available in the market, that can increase the shelf life of the fuel inside a tank.

Shantonil Nag

Shantonil brings a refined blend of expertise and enthusiasm to motoring journalism at With a career spanning over 11 years, he anchors Cartoq's insightful car reviews and test drives. His journalistic journey began as a correspondent at, where he honed his skills in content writing and scripting car reviews. Later, as Senior Editor for, his expanded role included curating and structuring web content. At, his expanded role includes assisting the video team to create high-quality car reviews. (Full bio)