Aftermarket / Bolt-On Options
 

Rather general question here... are there any aftermarket or bolt-on options that [generally] increase mpg rather then make them drop?

General stuff here, air intakes, exhaust kits etc... I've done basic work before, and I'm aware most of these items are meant to increase power and therefore usually drop mpgs if they affect them at all... but I'm wondering if there are any that can prove to be beneficial.

As an example, K&N often states that using their filters often increase gas mileage. In a Civic VX, everything is made to be optimal... so while replacing the entire intake would likely be a bad idea, would changing a stock filter to an K&N possibly be beneficial?

In the exhaust category, I'm aware that back-pressure is necessary to maintain a certain equilibrium... but does that mean that exactly the stock percentages are by far the best option? If I wanted to replace a rusty/rotting exhaust, are there any aftermarket stainless options that maintain the same sizes, if they are indeed optimal?

Since I'm just blurting out a few specific ones... anyone know anything about light-weight pullies, such as aluminum/billet A/C, alternator, or camshaft pulley?

I've been here since 2008 and I don't remember seeing any bolt-ons that will pay for themselves, or even any that will produce a good chance of measurable fuel economy increase regardless of cost.

Absolutely... but not what you think.

scangauge 2 (ScanGauge - Trip Computer + Digitial Gauges + ScanTools)
ultragauge (UltraGauge Automotive Information Center and OBDII Scan Tool)

these are small computers that read your OBD2 codes and stream data from your ECU so you can monitor your current MPG along with a plethroa of other things.

I have done intake, exhaust, header, aluminum crank pulley and though they state that they do increase mileage, i will agree with holycow and say that they do not pay for themselves. I did all those things for power.

the scangauge also adds quite a bit of power too....cuz knowledge is power. (cheesy statement for the day)

You could possibly get a lightened flywheel but the cost probably isn't worth it. I got a k&n but it was free not sure if it helps or not.

The k&n is only going to help with the replacement costs vs the standard filter in a daily driver. Had one in the wife's car, and with only 5000 miles a year use, it wasn't worth the effort.