I got worse fuel mileage with a grill block

[pasadena_commut]

Originally Posted by MetroMPG

Nope.

Why not? The grill is big and flat, and has huge holes in it. It looks like maybe the Jeep was designed for a lot of flow through the grill, past the motor, and out the bottom of the engine compartment and/or the wheel wells. So blocking the grill would stop that flow, resulting in a big high pressure area sitting in front of a planar surface, which could result in more drag. It isn't like a passenger car, where the grill is smaller, and the front of the car more aerodynamic to start with.

[dichotomous]

you could try using a flat angled sheet of plastic from the front edge of the bumper to the top of the grill, maybe clear plastic and youd get you headlights to shine through. also smooth out and fill in the gap between the bumper and wheel wells, throw an airdam on there that covers the front wheels as much as possible, and if you have skinney tires and flares, 4 wheel skirting would help.

though, I dont know how much all that would do. your biggest problems are the engine and drivetrain, neither are efficient at ALL, but then again they are rugged and tough

[winkosmosis]

I think people on this forum put too much stock in grill blocks. They think that because the air going through the radiator and engine bay is turbulent, having the airflow slam into even a vertical surface is somehow better. I think if anyone here had a jet engine, they'd try to block the intake "because flow through a jet engine is turbulent".

A grill block may improve aerodynamics on some vehicles, but on a Wrangler, airflow is gonna hit that grill block, and fan out.

To see what I'm talking about, hold a knife horizontally under a running tap. Now hold a fork under the running tap to simulate a grill.

[winkosmosis]

You should try an angled air deflector attached to the bumper. You can extend it downwoard to deflect flow under the front axle, and attach a bellypan to the crossmember to deflect air under the rear axle

[getnpsi]

a vehicle has to already have some aero properties to benefit from a grill block. sealing the front up helps its aero. with a brick all you are doing is blocking radiator. Helps it reach operating temps faster. Its not doing alot of diverting air. You'd need a nosecone or what others are posting IMO. I would do simple cardboard rad blocking, and also work on sealing up the underside.