With respect, that's not a very good test with fudging numbers and guessing. I'm just saying that on mine, I haven't scientifically tested it, but I *definitely* would have noticed a 20% drop in mileage and that hasn't happened, I would often reset the mileage meter on my way home with my bike on the rack and I'd still get the same numbers as usual. There's a certain margin of error in there...but not 20%, I undoubtedly would have noticed that.