Jeep Grille Blockoffs
 

So I had a significant increase in fuel mileage from 15 to 20mpg in my 2000 Jeep Wrangler. This last tank was on roughly the same split of highway/country/city roads I do every day. The ONLY thing I did different as an experiment was block off 4 of the 7 grill inserts with tape to try and raise the temp since it struggles to get to temp quickly even in the summer with a 195* thermostat. I did not see much change in engine coolant temps except at highway speeds it did get a but hotter, but still at a very safe temp.

Stock sized 31” AT tires and just a .75” lift up front and a 5.3 LS with headers. Also added a bug deflector which really took the wind rush down a lot so I assume it routes air over the flat windshield pretty well. Before this even if I tried really hard for mpgs, I would maybe get 16.5mpg. I went and checked that I filled up all the way and mapped out my drives on this tank to verify the numbers were correct, and they were.

So has anyone seen such an increase with something like this alone on a brick like vehicle?

An increase of 33% seems unlikely.

Maybe an A-B-A test?

Im with you very unlikely, but on my try hard days its never been anywhere near this high. Like I thought my gas gauge was broken since it was barely moving where it usually sits at certain miles. Tomorrow ill be going back to work and my normal commute and will see what it ends up being after the end of this week to see if its repeatable. But in the back of my head I still think there might be something to this since the tank before did have the grill block offs but most of the miles was driving with no hood at all on the highway since I was going to buy a hood, or towing a trailer through every redlight in the city and still managed my pre-grill block off average of 15.

I’d like to try it on my 1990 F150; also a brick shaped vehicle, and I typically get about 12mpg, and 14 on the highway. It’s pretty miserable, so I’d like to see how it goes. Would probably just block off the radiator side the AC is on and keep the radiator side open. Worth noting that the truck still has an engine driven cooling fan.

If this does actually work as well as I am hoping it did, I may make some custom grille inserts with flaps that are connected to a little motor that will open when triggered from the fan 2 output so that if it does get too hot ill get full airflow to radiator.

Yeah I don’t think I’d go crazy and limit the air going to the radiator. Maybe a half block off for the winter, but not during the summer. We get 90+ degree days here regularly.

Same, we have had a few days of high 80s and its maintaining temp just fine. Maybe not so well when I have my trips in the desert but so far is showing to work well in mid OH.

Just remember that factory grill openings and radiators are sized for 100 degree days with high humidity while sitting in bumper to bumper freeway traffic. There is a lot to gain aerodynamically for someone that is paying attention. You can probably block at least half the grill if you are aware of the operating temps.

Good to know. I’ve made some grill plates for my civic just now, but I’m waiting for the paint to dry and I need to find some decent screws and a couple long bolts. I’m relocating my front license plate (required in Virginia) to serve as part of the grill block off plate. Will post pics tomorrow when everything is installed. I used some thick plastic siding or molding or something that I found.

aero mods and mpg
 

On my CRX, there was a natural variability of between 36-mpg, and 82-mpg, depending on 'routes' and 'weather', and this was without any changes to the car after modifying.

Just shooting from the hip, even if you completely blocked off the radiator, it's unlikely that you'd realize anything beyond a 3.5% mpg improvement. That would be at a steady 70-mph.