Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - I got worse fuel mileage with a grill block

bombloader · 12-01-2008, 01:21 PM

I put a cheap grill block on my jeep(plastic sheeting and duct tape.) I wasn't able to do a formal A-B-A test on it, but it was mostly a proof of concept to see if the vehicle would over heat. I left it on for a trip to Montana recently. On the first two legs, I posted 14.9 and 16.1 mpg. This is the worst hwy mileage I've posted since I began hypermiling the jeep. Both of these were level stretches of freeway with some rolling hills. I removed the grill block for the rest of the trip and mileage improved to 18.4 on the next leg. The next leg was windy mostly two-lane, and a had an approximately 3 mile 6% grade in it. I know this isn't a very scientific test, because the roads changed between runs, but I would think the third leg would be worse for economy than the first and second. Also, the fourth leg was very similiar to the first and second and I again was over 18. I have two hypotheses for these results:
-The grill block decreased airflow too much, so the fan worked more and the extra drain on the engine canceled out any aerodynamic savings.
-Either myself or the road introduced enough variation that the test is just invalid.

Has anyone here had experience with grill blocks on 97-2006 Jeep Wranglers(TJ series)? If you have, what effects did you notice on fuel mileage? I'd like to gather some more info on this vehicle before I run more tests of my own. If I cant get anything, I'll probably run the block again with a larger opening too see if I get different results.

12-01-2008, 01:21 PM	#1 (permalink)
bombloader EcoModding Lurker Join Date: Nov 2008 Location: boise id Posts: 64 The XT - '92 Yamaha XT225 Serow Last 3: 80.67 mpg (US) White Civic - '08 Honda Civic Hybrid 90 day: 38.23 mpg (US) Blue and White Beast - '78 Ford F150 90 day: 11.33 mpg (US) Red T100 - '93 Toyota T100 90 day: 14.7 mpg (US) Thanks: 1 Thanked 5 Times in 4 Posts	I got worse fuel mileage with a grill block I put a cheap grill block on my jeep(plastic sheeting and duct tape.) I wasn't able to do a formal A-B-A test on it, but it was mostly a proof of concept to see if the vehicle would over heat. I left it on for a trip to Montana recently. On the first two legs, I posted 14.9 and 16.1 mpg. This is the worst hwy mileage I've posted since I began hypermiling the jeep. Both of these were level stretches of freeway with some rolling hills. I removed the grill block for the rest of the trip and mileage improved to 18.4 on the next leg. The next leg was windy mostly two-lane, and a had an approximately 3 mile 6% grade in it. I know this isn't a very scientific test, because the roads changed between runs, but I would think the third leg would be worse for economy than the first and second. Also, the fourth leg was very similiar to the first and second and I again was over 18. I have two hypotheses for these results: -The grill block decreased airflow too much, so the fan worked more and the extra drain on the engine canceled out any aerodynamic savings. -Either myself or the road introduced enough variation that the test is just invalid. Has anyone here had experience with grill blocks on 97-2006 Jeep Wranglers(TJ series)? If you have, what effects did you notice on fuel mileage? I'd like to gather some more info on this vehicle before I run more tests of my own. If I cant get anything, I'll probably run the block again with a larger opening too see if I get different results.