Propane smell????

[Bondage]

After having a full service done a couple of weeks or so ago on my '03 H2, I began to notice a strange odor - kinda like propane or natural gas - while driving with the windows down. I asked the tech about it, and he said it was just diff fluid that probably spilled a little when they were filling it. He seemed to know exactly what I was talking about and I bought the explanation. BUT - it has been a couple of weeks now, and the smell is stil present. Does this sound familiar or right to you guys? There is nothing leaking - at least not to the point of dripping in the driveway or being noticeable when I get down and look under the rig. With the recent rains, anything there should have been power washed away! So why the hell does my sweet looking rig smell so sour???
Anybody?

Sean