Riesling is often described as "racy." The term usually refers to its high acidity but is even more apt when the same wines have that slight whiff of racing fuel. What causes this? Bottle aging and warm weather are two reasons most often given, but it's more complicated than that. Isn't it always? If you're curious, Tom Stevenson has an fascinating article at the Wine-Pages that goes into detail on how Riesling takes on diesel or petrol flavors. One excellent Australian Riesling that has a nice touch of diesel fuel running through it is the Petaluma Hanlin Hill Riesling. I recently had the 2006 which had wonderful notes of lime and honey with a nice light whiff of fuel on a lithe frame of racy acidity.