The jury is no longer out on them.....They HELP big time and the return on investment is very short at todays fuel price. We just did a 1000 mile trip in the toad and I was amazed at the number of OTR trucks that have now installed them. I would say that on our fuel stops and looking at the trucks we passed, at least 30% of the trucks in the had them on the tractor and over 50% on the trailers. Drivers I have talked to are reporting a ½-1½ mpg gain. If you are a full timer and put on 12-15K miles a year, the $220 would return in a hurry.