I havent done much yet but i have seen an improvement in mileage since purchasing a scan gauge and being mindful of my instant fuel consumption. Now more recently i have added some light aeromods to the car and increased fuel economy from 33-34 before the scan gauge to 39 and change after the grill guard and gauge. the commute consists of essentially 15 miles medium city driving and 30 miles of rural highway driving.
Im not saying the grill guard was responsible for the majority of this, i have certainly adjusted my driving style as well as reduced my highway speeds in an effort to save fuel on each trip. but with the addition of the grill i have certainly seen an increase in mileage at the pump.
Since everyone loves pictures here's the vehicle with first grille guard in temporary form (got some weird looks and a lot of questions at work).
Notice the lower partial block is only on one side, originally i had them symmetrical on both left and right. however on my first test run (across the state) i noticed intake and water temps exceeding what i was comfortable with. AIT was reaching 130 before the electric fans would cool the engine bay. So i removed the driver side block which was inline with my air intake, at stop lights on hot days my temps still get into the 120's but will drop quickly at green. I am considering adding more lower blockage in winter.
To this: As you can tell I painted coroplast and secured it with fishing line and some clear tape on the lower grill.
from another angle
Needless to say my girlfriend approves of the new look in comparison to the blue tape before lol