I had an exhaust leak on my wagon that got sucked into the car everytime I opened a window or the sunroof. It was the same location, front of the front muffler. The smell though was exhaust, not burning oil. You may also have a drip from the tranny or turbo that is hitting the exhaust and burning so it's not oily looking. You can usually see the residue of burned oil if you look carefully enough.

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LRG
1987 300D Turbo 175K
2006 Toyota Prius, efficent but no soul
1985 300 TDT(130K miles of trouble free motoring)now sold