I know this is an old post, but...

ORANGE DEGREASER!!!

I found a product at the Home Depot called Nature's Orange. The label said it was OK for treating laundry stains and for using as a laundry booster. I poured about a cup into the wash and nothing else. I did that about 3 times and the gas smell is gone. To get rid of the orange degreaser smell, I did a few plain white vinegar washes, then regular detergent & fabric softener.

NOTE: This was AFTER I tried detergent, white vinegar and baking soda (and various combinations thereof) in about 7 washes, all to no avail. The orange degreaser came to me as an inspiration after I read that since gasoline (petrol) is an oil-based product, I should try an oil-based solution. I was about to use baby oil (which I read about) when I thought about the orange degreaser idea.

Anyway, if you want to try this, I just recommend reading the label of whichever orange degreaser you find & err on the safe side - make sure it's OK for laundry use.

OH - remember, if you think your clothes may still smell a little of gasoline (like you're not quite sure) just DON'T put them in the dryer as the dryer may spark a fire. Line dry and air them, and then do a sniff test after.

GOOD LUCK to anyone else who may need this in the future!