If you have a big, gas hungry truck what can you do to save on gas? Well, one option could be the use of low friction synthetic oils. This video shows a dyno test run with a synthetic oil called Royal Purple. The dyno showed that immediately after replacing the oil with the Royal Purple synthetic the drive train friction was reduced. You might want to try it out too. One thing to keep in mind is that if you are replacing old oil, you could see an improvement without a synthetic. Oil oil is probably going to result in more friction than new oil. So on the dyno, you would really want to empty the old oil, replace it with new oil and then run the numbers. Then replace the oil with the synthetic and see what numbers the dyno posts up. Then you can compare fresh oil to fresh synthetic. The use of a dyno makes this result valuable. Only a dyno can give you a clear number.