Originally Posted By: DBMaster
I would like to merely suggest that there are a wide variety of effects that are experienced with intake and exhaust mods. I think it quite plausible that your mods have reduced the car's fuel economy.
The most common effect from said mods is the increased amount of time spent pressing the GO pedal, in order to hear that intake / exhaust ROAR! This obviously results in the MPGs taking a hit.
Having said that, my Mazda 3 returned the same MPG average when it was stock. Nothing changed with the addition of the intake & exhaust modifications during none stop highway trips from Florida to North Carolina (400 miles) which me and the wife take often.
From past experiences, the addition of an aftermarket intake & exhaust resulted in the engine now breathing in air with less restriction and burn exhaust gases now exit with less restriction so in essence, the engine became more efficient vs stock and I saw MPG gain with both vehicles, once modified. My 2007 Civic Si & 2006 Scion tC are those examples. Both cars would EASILY surpass the EPA ratings by 2-3 points during the EXACT SAME FL - NC highway trips, where the car is on cruise control the entire way at the same 76mph.
I expected the same from the Mazda 3, or if the OEM intake & exhaust are too restrictive, the addition of the mods shouldn't have changed the way the engine operates and the gas mileage should be the same.
There's a "Real World Highway MPG" poll over on the Mazda forum and the majority of the results should that people are in the 34-36mpg & 37-39mpg range. Only about 11% are above 40mpg on the highway. Those 11% most be driving 65mph or some other favorable driving condition to achieve those numbers, because 90% of the other members on the forum can't do it, just like me.
Don't blame the modification.
By the way, the car is also lowered by 2" and this should result in less drag while at highway speeds, which should technically HELP my fuel economy yet I'm still struggling to get above the mid 30s.