I just installed a ghetto cardboard prototype grille block on the upper grille only as per basjoos's advice. Basjoos is, after all, a hypermiling sage. The weather was a perfect 64 degrees, clear and sunny, so I had no excuse not to be outside fabricating. Here's a pic...

Let us know if you see any difference in mpg! I plan on installing a upper grill block when the weather warms up. Right now it is 19 degrees outside, so no way. :(

Hey tdh1283 im just up the road in Pflugerville and you're right it was a perfect day today. Sorry peakster:( . I've mounted my upper grill blocks on several car behind the grill with great success and it not visible unless you look real hard. Just use tie wraps to hold it in place.

***to the tune of 'paint it black'
i
see
a
grill
block
and
i
want
it
painted
bla-ack

Does it look like the benefits are a combination of
1) keeping the engine warmer
and
2) aerodynamic improvement, getting that air to skip over the top of car instead

In my car ('89 Volvo 240) I can't seal up the grill because that's where my modified air intake gets it air. But I can partially block off the radiator. I'm thinking something like a plastic or aluminum screen that's maybe 80% closed, 20% open holes.

What to you people think?

hmm... with a volvo it might be better to somehow smooth off the sharp edges, but who knows it might work. there are a few good ways to find out :)

the mod is more for aerodynamics.

Yeah, I have a Dremel-type tool. Cut and grind!
Actually the 240 has rounded edges + corners. The 740 model had the sharp corners. 240 wagon has a rounded brick shape anyway, the only way to change that is with a hammer...

I have a few ideas but they will have to wait for warmer weather. Still in the 30's (F) here in CT! I think I can put some stiff plastic or aluminum on the back side of part of the grillwork; that will help the aerodynamics. Paint it black and it will be nearly invisible.

I might still put a screen over the radiator. But it has to be vibration-free so it won't kill the radiator. Maybe put it over the non-functioning ac condenser if the work access is easier.

Then I'm still thinking about some underbody panels as posted by tjts1. He did it on a 960 which has a different layout but there might still be a way to do it. For me, any project requiring laying under the car to work on it tends to get shoved to the back burner.

It's been a while, do you have any updates? I want to do this some time this spring. Did you leave the covers as is or did you freshen them up abit to match the car more?

One of the problems I have with my grill block is that around town at low speeds there isn't a lot of heat being generated by the engine because I am not burning a lot of gas but as I hit 40+mph the gas usage goes up and so does the heat. SO I was thinking that I need to automatically open the grill block more at higher speeds and it dawned on my to make a flexible grill block that bends open as the air pressure increases. If made of something that is temperature sensitive then on warmer days it could even become more flexible and open easier at a lower speed to compensate for the greater need for cooling.

I guess you could stick forced air heating vents in the grille and run a choke cable into the cabin to operate them.