A friend of mine has ans 06 Jetta and the oil smells strong with diesel fuel. He said it smells like he just pumped it into the crankcase. He said he has not observed any unusual smoke or general running problems. Any insight into this would be appreciated. The car has 1,000 miles.

There's a quick and dirty test to check for that. Get a paper towel and place a drop of the suspected engine oil on the towel. If I recall correctly, the positive test for diesel in the oil is when the drop separates on the paper towel.

Have your friend also check that the engine coolant isn't low as that has been known to leak into the engine oil compartment.