Performance mods that won't affect/will hardly affect gas mileage??

[BailOut]

Performance mods come in different flavors. One you may not have considered is a solar trickle charger, which also helps FE.

By keeping the battery topped off during the day and then continually contributing to its charge level while running around, even just in a minute amount, is that much less time the alternator needs to place a load on the engine every day.

Any energy not used by the alternator is that much more of the "natural" energy the engine produces that is available to you, and you are saving fuel because the engine doesn't have so much of an external load on it.

Another mod that becomes a performance mod by proxy is an engine block heater (EBH), which also makes a noticeably positive impact on FE.

How this becomes a performance mod is in its engine protection. Once you start using an EBH it's a rare day that you perform a "cold start", which is hard on an engine regardless of what oil or additives are used. By keeping the engine healthier and happier it will keep putting out at 100% for much longer.

This also saves lots of fuel because the days of the ECU/engine running extra rich at extra high RPM in a race to get the fluids and emissions system warm after a cold start will be gone.