(No longer as of March 2017)***************************************************I was excited to receive this and immediately set my marine battery into it. Ive only had these for one day and used them for about 6 hours, will continue to update as I use them more. It took about a week or so to do so. I do it every night to wireless charge it. If I remember anything else I put it here. 5 bzw 10. Now, at three pairs later, she is still excited for pajama time every night. Great mic for audio book recording Other than that, good for the price and much better than some of the other spice racks I ordered. Gas mileage? I dont feel gas mileage should be a consideration since its a aftermarket product.