I read of a case where this guys wife was adding petrol to the wash so that he would get used to the smell and then when she later dowsed him she could strike a match without him wondering why. He was pondering the smell one day and was deep in thought when a friend said "a penny for your thoughts".
I would second that. Perceiving a burning rubber smell can be a symptom of a certain kind of brain tumour. I don't know if a petrol smell can be indicative of a similar condition, but would want to find out if it were me.