Hi,
My guess is that the zigzag tape has boosted the FE 1 (and maybe as much as 2) miles per gallon. My previous tank was ~44.5mpg, and currently the
SGII sez ~46.6mpg -- some of that difference was running in the rain for part of the tank.
I don't think that the tape will come off in water -- rain or by washing. It is Gorilla tape, after all.
The other improvement in my driving has been accelerating for 3-5 seconds at the top of a hill, to improve the coasting down the hill. A version of pulse & glide; when it has the best payoff.