About 5 years ago we were working at our construction shop. A young Black guy, looked enough like Michael Jordan to be his twin, drove up, flashed his ID, and said "I want to check all your trucks. " He did and found nothing illegal. He was with the IRS, and checked every construction truck in the area. At that time the fine could be up to $25,000. 00 according to him. We have been checked at weigh stations several times. Its too risky to run off road diesel. Our checks always involved a clear plastic tube, inserted into the tank and then withdrawn with several inches of fuel. Back then I used a red fuel supplement, and it did tint the fuel somewhat. We discontinued that pracatice in a hurry after being checked.