Reply #58: I'm sorry but you're mistaken..

[Jonathan50]

"What about modified, or hotter burning spark plugs that decrease the amount of "blow by" (unignited fuel)?"

"Blow by" is the combustion gas which leaks by the piston rings and enters the crankcase, which is why cars have (or had?) PCV or Positive Crankcase Ventilation valves.

<nitpick> Actually it's unignited fuel air mixture, not just fuel, fuel must be mixed with air to burn. </nitpick>

"How about if they replaced the big all terrain tires with a good set of radials? (this improved the mileage on my truck by at least 9 mpg."

Were the replacement tires smaller in diameter than the all terrain tires?

That can fool you into thinking you're getting better gas mileage than you really are. Smaller diameter tires mean you don't go as far on each wheel revolution but your odometer will still read the longer distance unless you have the speedo calibrated.