add more mile to my car?

Don't waste your time or money on any "device" that claims it will increase your fuel economy.

Good luck getting more miles per gallon in your F-250 Super Duty pickup. We have a 2001 Ford F-150 Supercrew 4x4 (average 16 miles per gallon due to mostly city driving) and a 2006 Ford Escape Hybrid (average 31+ miles per gallon).

Your best ways improve your fuel economy in any motorized vehicle are to --

• Reduce Power Demand:

• slow down

• drive at a smooth, constant speed; avoid jackrabbit starts (you'll just get to the next light/stop sign a couple seconds faster than the other guy...)
• accelerate and brake moderately

• use cruise control in flat areas

• Reduce Loads & Losses:

• combine errands/trips

• don't carry unnecessary weight
• avoid extra drag
• minimize temperature extremes when vehicle's parked (tint windows; get & use a sunshade; if safe, leave windows cracked in hot weather; air out vehicle when you return before starting AC so you don't have to blare it on high for ages)
• check tire pressures often to maintain optimal pressure; too low & you'll have lower fuel economy & risk of puncture/blowout
• perform all regularly scheduled maintenance items
• limit accessory usage (AC/defroster/seat warmers/etc. if not needed)

Source: personal knowledge & a little laminated "How to improve your fuel economy" card that I received when we bought our Escape Hybrid.