Originally Posted by stanw909
Will try that but evry radar sign since I bought the van can't be wrong in exactly the same way can they?
The radar sign will give you the speed accuracy, but it is not necessarily related the odometer. So if you want to confirm your gas mileage, you have to check the odometer. You can use gps, or the mile markers others have suggested. If you use the mile markers, be aware that many of them, especially older ones before gps positioning, may be a bit off location. We always will us a minimum of a 30 mile test, and then check every mile for 10 miles to see if they match the same amount off. If they do you are good, if not, try the next 10 miles again.