If you want to take a chance of self-combusting then yes you can put petrol on your body however, I do not recommend you putting any gasoline on your body. Instead, why don't you try the lotions at your local drugstore which gradually darken your skin. These are not self-tanning products.
Petrol, or gas, put on the skin will dry out the skin. It takes all the natural oils out of the skin. This can lead to skin problems, sometimes even cancer when the sun hits it. Try some of the cans of "tanning" lotions, etc.....not gas.