Remember you will be putting an additional 25 - 30 amp draw on your electrical system - at idle, which could necessitate an alternator change. If you have to run the fan with the engine off because of an over heat, you got "other" cooling system problems that you sure don't want to deal with on the street. Some of the HP losses quoted with a mechanical fan are way on the high side (IMO) and usually don't take in to consideration the HP loss caused by the additional 25-30 amp draw that the alternator has to supply. Due to clearance issues with my street rod, I have to run a 16" electrical fan. Draws 24 amps and I can actually watch the rpm drop when it kicks on. Unless it has been damaged, Flex fans are as reliable as any metal fans. Mine sees 7K at the track all the time.