It sounds like you've got more of a problem than just a fuel filter if you're only getting 10 mpg. You need to get all your maintenance items taken care of if they haven't been - ignition components, fluids, filters, timing adjustment, etc., then look at it further if it's still getting poor mileage.

Going to an electric fan isn't going to give you any better mileage or more power than a correctly functioning mechanical fan and fan clutch - any mechanical resistance you may lose will be more or less be made up for by the additional drag from your alternator as it powers your electric fan.

Your time and money will be far better spent by getting your engine running properly than on installing an electric fan.