[wmjinman]

I neglected to mention I pumped up the tires between the first "baseline" tests at different speeds and the tests yesterday. I attribute the 1.3 mpg improvement to that. Wow, now that I think about it, that's almost as much improvement as the grille block!! And it's not as though my tires were "low" before (all over 40psi and one of the the fronts almost 50). Before yesteday's tests, I put the fronts at almost 55, and the rears at 50.

When I saw my engine was getting hot (after the first set with the grille block), I used my roll of duct tape as a guide & traced out a 5" hole in the middle of the air dam to let air into the radiator. As I mentioned, I left the engine running the whole time yesterday, and when I put that cardboard up to the grille, it got "sucked" onto it, so I knew it was blocking airflow. Afterwards, the temp stayed around 228 -229, sometimes dropping to 224 F. - and it was "boiling over" and draining onto the ground after I got home & parked. And I needed to put more water in it once the radiator sucked the reservoir dry. So before starting it this morning, I enlarged the vent hole to 6 1/4" and will see how that works.

raylit20;

Thanks for that info confirming my 40 mph "best speed". One thing I noticed was that the RPMs seemed to be the same at 35 as 40. I thought maybe the "lock-up" torque converter just hadn't locked up or something. But not going into OD explains it, too.

Low 20s on the highway is what I would usually see, however the speed limits around here (depending on which road I take), can be up to 75 mph. My first day's test showed 23.7 at that speed, and that's probably about what I'd usually get.

Mine is a 4-door, though. Otherewise, they're probably about the same. I've also got the factory roof rack. Thinking about seeing what difference it makes taking it off, but I'm gonna guess it will be very little - similar to folding the mirrors back. However, I don't use it nearly as much as I use my mirrors! LOL!! Did you see any improvement when you removed yours?