As of 2007 federal law passed new legislation to have all new model engines to pass stricter emissions. With ULSD(Ultra low sulfur diesel) you have what it says lower sulfur count which is around 10 to 15 ppm against 50ppm in LSD(Low sulfur diesel). I think its great to have this so we can move towards a cleaner fuel. At least we can take the steps to a cleaner tomorrow. I believe i get better fuel mileage in my truck anyway burning ULSD. Which is a good thing consider i have a high horsepower motor which gets around 5.5 miles to a gallon of diesel.