Hooniverse Asks- What Mileage/Performance Legends Do You Believe?

Nitrogen in your tires, driving with the windows up for better mileage, and even attempts to defeat daytime running lights to recapture the incremental alternator load- there’s tons of myths and legends out there about ways to improve your car’s performance and mileage. Some of them seem pretty reasonable at first glance- buying gas in the cool of the morning so you’ll get a more dense – and hence more fuller – tank. But when held under the cold hard light of critical examination, most of these prove fruitless wastes of both time and money. But are there any to which you ascribe?
I was talking to a guy yesterday who religiously uses only nitrogen in his tires, and Evans Waterless coolant in his radiators. He believes that the absence of water in the cooling system will prevent engine degradation  from galvanic corrosion. Maybe he’s right, maybe not, but as all the major manufacturers recommend a mix, I think I’ll demur to the $30-$40 per gallon cost of the Evans.
Other performance and mileage tricks are a little more of head scratchers. There’s the air cleaner flip, the vortex intake discombobulater, and the magnet on the fuel line to de-cluster your hydrocarbons. Adding all of these to your car would conceivably make your car Veyron-fast and cause it to generate fuel rather than consuming it.
Of course, many of these gadgets have been tested and proven not to work, but that doesn’t stop thousands of them from still being sold each year. That’s because everyone wants to get better performance -whether of the tire-chirping or fuel-sipping variety – and they want to be able to one-up the neighbors.
So, what’s the sage-recommended trick that you swear by in getting the most out of your ride? Does it involve add-on parts with some sort of voodoo magic? Or is it a driving style that make you faster or able to go longer between gas stations?
Whatever the trick, does it work?
Image source: [GlobalUnlimited,  TornadoAvalanche]