Gas Mileage
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Platinum Member
Joined: 05-09-2006
Posts: 6,805
From: "Upland" Mesa, Arizona
Because this is a related topic to gas mileage, I'm going to introduce a new theory to this equation. I welcome comments and criticisms .....especially from the engineers, and technically inclined.
I noticed, on my recent vacation trip, a lot of disrupted airflow in the front of the car. Specifically about 12-18 inches in front of the "snout" of the hood. What I witnessed on the road is slightly contrary to wind tunnel tests.
I observed all this watching "butterflies" and the like, flying across the road in agricultural areas. Those creatures, in that area, seemed to be pushed to the side, very abruptly. While those lower and above, probably either struck the grill/bumper area or the windshield.
Those that were pushed aside appeared to be pushed forward then to the side. Which makes me believe the airflow currents dam up, then plow, then push. This all happens very rapidly at 65 MPH (this is the part that was contrary to the "smoke" wind tunnel tests that I witnessed at GM). Wind tunnel tests that I observed (not on the HHR) allowed the smoke to nearly engage the front of a vehicle much closer, then follow the dynamics of the design (although the smoke flow was slightly disrupted and flow pattern "thicker" in that frontal area.
So after all this commentary the point is......these cars are NOT air flow dynamic. The faster you go the less fuel mileage. I know, I know...just common sense. But again, some people think the faster they go, within certain limitations, the better the gas mileage.
Joe, Cleveland, Tony, Bob...anyone????
I noticed, on my recent vacation trip, a lot of disrupted airflow in the front of the car. Specifically about 12-18 inches in front of the "snout" of the hood. What I witnessed on the road is slightly contrary to wind tunnel tests.
I observed all this watching "butterflies" and the like, flying across the road in agricultural areas. Those creatures, in that area, seemed to be pushed to the side, very abruptly. While those lower and above, probably either struck the grill/bumper area or the windshield.
Those that were pushed aside appeared to be pushed forward then to the side. Which makes me believe the airflow currents dam up, then plow, then push. This all happens very rapidly at 65 MPH (this is the part that was contrary to the "smoke" wind tunnel tests that I witnessed at GM). Wind tunnel tests that I observed (not on the HHR) allowed the smoke to nearly engage the front of a vehicle much closer, then follow the dynamics of the design (although the smoke flow was slightly disrupted and flow pattern "thicker" in that frontal area.
So after all this commentary the point is......these cars are NOT air flow dynamic. The faster you go the less fuel mileage. I know, I know...just common sense. But again, some people think the faster they go, within certain limitations, the better the gas mileage.
Joe, Cleveland, Tony, Bob...anyone????
Senior Member
Joined: 03-31-2008
Posts: 772
From: CLEVELAND
Because this is a related topic to gas mileage, I'm going to introduce a new theory to this equation. I welcome comments and criticisms .....especially from the engineers, and technically inclined.
I noticed, on my recent vacation trip, a lot of disrupted airflow in the front of the car. Specifically about 12-18 inches in front of the "snout" of the hood. What I witnessed on the road is slightly contrary to wind tunnel tests.
I observed all this watching "butterflies" and the like, flying across the road in agricultural areas. Those creatures, in that area, seemed to be pushed to the side, very abruptly. While those lower and above, probably either struck the grill/bumper area or the windshield.
Those that were pushed aside appeared to be pushed forward then to the side. Which makes me believe the airflow currents dam up, then plow, then push. This all happens very rapidly at 65 MPH (this is the part that was contrary to the "smoke" wind tunnel tests that I witnessed at GM). Wind tunnel tests that I observed (not on the HHR) allowed the smoke to nearly engage the front of a vehicle much closer, then follow the dynamics of the design (although the smoke flow was slightly disrupted and flow pattern "thicker" in that frontal area.
So after all this commentary the point is......these cars are NOT air flow dynamic. The faster you go the less fuel mileage. I know, I know...just common sense. But again, some people think the faster they go, within certain limitations, the better the gas mileage.
Joe, Cleveland, Tony, Bob...anyone????
I noticed, on my recent vacation trip, a lot of disrupted airflow in the front of the car. Specifically about 12-18 inches in front of the "snout" of the hood. What I witnessed on the road is slightly contrary to wind tunnel tests.
I observed all this watching "butterflies" and the like, flying across the road in agricultural areas. Those creatures, in that area, seemed to be pushed to the side, very abruptly. While those lower and above, probably either struck the grill/bumper area or the windshield.
Those that were pushed aside appeared to be pushed forward then to the side. Which makes me believe the airflow currents dam up, then plow, then push. This all happens very rapidly at 65 MPH (this is the part that was contrary to the "smoke" wind tunnel tests that I witnessed at GM). Wind tunnel tests that I observed (not on the HHR) allowed the smoke to nearly engage the front of a vehicle much closer, then follow the dynamics of the design (although the smoke flow was slightly disrupted and flow pattern "thicker" in that frontal area.
So after all this commentary the point is......these cars are NOT air flow dynamic. The faster you go the less fuel mileage. I know, I know...just common sense. But again, some people think the faster they go, within certain limitations, the better the gas mileage.
Joe, Cleveland, Tony, Bob...anyone????
I also noticed that in a stiff headwind, 40 mpg is not achieveble at 55mpg, i need to go slower, which is too slow to maintain traffic flow.
Anyone seeing better mileage at 60 than 55, 65 than 60 or 70 vs 65 is wrong imho.
Senior Member
Joined: 07-16-2008
Posts: 183
From: Edmond, OK
Got back from the Road trip last night about 8. here are some highlights. (I'm going off of Memory here so these figures may change) 
I'll post some more with a little more detail when I get home.
- OVERALL Average MPG was 30.11 for the 1200+ miles
- High was 33mpg
- Low was 27
- There was no need to run the AC until about 3pmCST on the first day. (Seriously, It was a gorgeous day for driving and I love the sunroof.)
- I filled before leaving and filled In York, Nebraska. Not because I had to, but because we had to stop to "empty some tanks."
Per the DIC, I still had 119 Miles left in the tank. 
- After Filling up, we got the Tank miles up to 504miles.
- As I was Exiting the interstate, My Fuel Econ switched to 30.0. (It reads 29.8 right now.)
I'll post some more with a little more detail when I get home.
Senior Member
Joined: 04-11-2008
Posts: 663
From: Eastpointe,MI.
It can be surprising how little things make noticeable changes to airflow.Case in point-several years ago I was on a wintertime trip to Acme,Michigan.We were travelling in my now ex mother-in-law's Grand Marquis.It was a cool,damp day.Water droplets were on the hood and as the air rushed over the front of the car the stand up header ornament split the airflow and created a dead air zone behind it so the water drops stayed put there(almost back to the cowl panel) but were blown off on the other parts of the hood.Fascinating to think how a little thing like that ornament could have such a noticeable effect.
Senior Member
Joined: 11-17-2005
Posts: 126
From: Springfield Vermont
I average 32MPH with my 2.4 manual transmission. (Recently did 33.1 for a 350 mile trip, mostly highway miles.) My wife averages around 28.5 with her 2.2 automatic with mostly in-town miles. Has hit 30 and change on Interstate trips.
Senior Member
Joined: 07-16-2008
Posts: 183
From: Edmond, OK
Ok I'm home:
Leg 1: Edmond, OK to York, NB
TRIP A: 379.9 Miles
MPG: 28.15
Spent: 13.494 Gal
Comments: Filled up in YORK, NB with No Ethanol.
Leg 2: York Neb to Vermillion, SD.
TRIP A: 192.3
MPG: 32.03
Spent: 6.004
Leg 3: Vermillion, SD to Salina, KS
TRIP A: 323.6
MPG: 28.57
Spent: 11.326
Comments: Filled with NO ethanol
Leg 4: Salina to Edmond, OK
TRIP A: 236
MPG: 31.67
Spent: 7.452
Again, we filled when the opportunity presented itself and it was reasonable to do so. I want to Point out that the tanks that were filled on the "good stuff" ran considerably better MPG-wise than those with the Blend.
Average MPG comes out to 30.11. The DIC read 29.0 getting off the interstate, When I pulled into the driveway, It read 28.9. Weather wise, there was a rainstorm in Wichita, That's about it.
Leg 1: Edmond, OK to York, NB
TRIP A: 379.9 Miles
MPG: 28.15
Spent: 13.494 Gal
Comments: Filled up in YORK, NB with No Ethanol.
Leg 2: York Neb to Vermillion, SD.
TRIP A: 192.3
MPG: 32.03
Spent: 6.004
Leg 3: Vermillion, SD to Salina, KS
TRIP A: 323.6
MPG: 28.57
Spent: 11.326
Comments: Filled with NO ethanol
Leg 4: Salina to Edmond, OK
TRIP A: 236
MPG: 31.67
Spent: 7.452
Again, we filled when the opportunity presented itself and it was reasonable to do so. I want to Point out that the tanks that were filled on the "good stuff" ran considerably better MPG-wise than those with the Blend.
Average MPG comes out to 30.11. The DIC read 29.0 getting off the interstate, When I pulled into the driveway, It read 28.9. Weather wise, there was a rainstorm in Wichita, That's about it.