So far, we filled 4 times before we used the cells and used 208 gallons over 770 miles which calculates to 8.50 MPG. All of this was in the lower 48 on both flat and mountainous terrains and driving both 65 on the interstate and about 50-55 elsewhere. I believe it represents a pretty good baseline. We began using the cells when we left Washington State and entered into Canada, and since that time we have filled 7 times, used 308 gallons of fuel and covered 2941 miles, which equals 9.53 MPG, or 1.02 MPG better for an improvent of 11.96% While there has not been any interstate driveing using the cells, we have covered mostly mountainous terrain at relatively low speeds with frequent slow downs and start ups on rough roads. My sense is that we have clearly seen an improvement using the cells at least equivalent to the above stats.