It's when I get behind them in traffic. My nose is real sensitive to petroleum products. A vehicle in need of a tune up really gets to me. YUK!! Burning oil or diesel smoke stays with me for awhile, like it gets stuck to the inside of my nose or something.
Back in the good old days I hopped into my buddies car and told him he needed to replace his fuel pump. He asked why. I said it was because it is leaking. When we got to where we were going I opened his hood and showed him the slight "wet" spot where the gas was leaking out. He couldn't smell it.