2.1 MPG Gain with Grill Cover at 70 MPH, 27F

[plus 3 golfer]

As some may know I purchased a set of grill covers from ptjones.  This morning with winds calm and temperature ranging from about 26-28F, I tested the covers over a 15 mile loop as follows after engine temp reached 85C+, with HVAC off, headlights on :

 

1) accelerated to 70 mph (GPS), set cruise (ECO)

2) reset Trip 1

2) drove about 7 miles with an elevation gain of 90 feet

3) exited the 4 lane divided highway to a stop sign, turned left and turned left again to the on-ramp

4) accelerated  briskly to 70 mph and resumed cruise before entering highway

7) drove about 7 miles with an elevation drop of 90 feet

8) noted Trip 1 data at about the same location when Trip 1 was reset.

9) repeated the loop 3 more times.

 

So, the data was loop 1 (no cover) 31.3 mpg, loop 2 (with cover) 33.4 mpg, loop 3 (no cover) 31.2 mpg loop 4 (33.3 mpg).  The test took slightly over an hour and the temperature was dropping.  When I started the test the ambient was 28F and when I finished it was 26F.  The EV use was 0.5 miles for each loop all when exiting the highway.

 

I took ptjones graph and added my two test points to it as seen below.   My data seems consistent  I got a 6.7% increase with the grill covers in place.  The coolant temperature runs about 5-7C higher with the grill covers on.  You cannot see this difference on the temperature gauge in the vehicle.  

 

I will repeat this test tomorrow morning and plan to run additional tests at higher temperatures. I plan to run a few more tests for  typical trips I make during the day.  I did try to run tests a few days ago at 55 mph, but the issue is that ICE shuts down and one runs on the battery.  So, there  needs to be some adjustment made to the data for the initial battery charge and ending battery charge.  For example, if one starts a test with a full battery charge and ends with it nearly discharged, one could see a significant change in fuel economy in a 15 mile loop.  If the car can run 1 mile between full and depleted charge, that amounts to 1 mile where no fuel was used or about a 1/14 or a 7% possible error. Similarly, if the car starts depleted and is fully charged at the end of the test, the car used more fuel to cover the 15 miles and the error could again approach 7%. 

 

I also want to say your mileage may be different and perhaps my additional test results will be too. :)  

 

 

 

[valkraider]

I learned something while playing with tuners for my truck. I burned more fuel playing with and testing the tunes than I will ever save with the slight increases in fuel economy...

[C-MaxJaxon]

The testing method is close to what I was thinking of trying, except for including steps 3 and 4 in the measurement. I wanted to completely eliminate driver influence by recording the mileage before turning the cruise off at the exit. So you'd measure the return half separately by resetting Trip 1 or 2 as soon as you're up to speed and the cruise is engaged again. Then combine or average the two trips.

[plus 3 golfer]

The testing method is close to what I was thinking of trying, except for including steps 3 and 4 in the measurement. I wanted to completely eliminate driver influence by recording the mileage before turning the cruise off at the exit. So you'd measure the return half separately by resetting Trip 1 or 2 as soon as you're up to speed and the cruise is engaged again. Then combine or average the two trips.

That is what I'd normally do but my guess is that the coasting plus battery operation offset the extra fuel used to accelerate and recharge. The point was to measure the difference in mpg not particularly the mpg at 70 mph. There was no question that the mpg differnce for the uphill portion at 70 mph was about 2+ mpg also.

I learned something while playing with tuners for my truck. I burned more fuel playing with and testing the tunes than I will ever save with the slight increases in fuel economy...

Yeah, I know especially since I have little use for this data at 27F in Phoenix. You've convinced me to forget about spending $7.50 for gas tomorrow morning to validate this cold weather performance. Edited January 12, 2013 by Plus 3 Golfer

[ptjones]

That is what I'd normally do but my guess is that the coasting plus battery operation offset the extra fuel used to accelerate and recharge. The point was to measure the difference in mpg not particularly the mpg at 70 mph. There was no question that the mpg differnce for the uphill portion at 70 mph was about 2+ mpg also. Yeah, I know especially since I have little use for this data at 27F in Phoenix. You've convinced me to forget about spending $7.50 for gas tomorrow morning to validate this cold weather performance.

I appreciate the good job you're doing.

[C-MaxJaxon]

A range of 31-33 MPG at 70 MPH seems very low. The trips that I've done with cruise set at 68 MPH on the highway have averaged between 37 and 43, depending on temperature and wind. Temps were typically in the 20s or 30s.

[plus 3 golfer]

A range of 31-33 MPG at 70 MPH seems very low. The trips that I've done with cruise set at 68 MPH on the highway have averaged between 37 and 43, depending on temperature and wind. Temps were typically in the 20s or 30s.

I only have 700 miles on the car (not broken in) but like I said this is consistent with the controlled tests ptjones ran. Look at the graph and you will see that your numbers are very high compared to the graph. The mpg difference between 70 mph and 68 mpg is likely around 1.5 mpg.  Also, It doesn't take very much of an elevation change to affect your mpg significantly especially in shorter trips. 

 

I suggest you run some controlled tests at 70 mph (GPS) and then post the results. I highly doubt one will see a significant difference in mpg between cars in a controlled test except for break-in mpg difference.  My speedometer reads higher than GPS speed (about 1 mph higher at 70).