How much does gas mileage drop as you go to higher speeds?

[Eos]

I'm pretty sure I have posted in every "mpg is better/worse going faster/slower" thread.

1996 Toyota Avalon
3.0L V6
4 speed auto
138k miles

First, visit my mileage page.
Look at the tanks on 2006-07-08. The first one is from Jerome, ID to Park City, UT with a stop in Roy, UT to sleep. Tank two is from Park City to Glenwood Springs, CO. Jerome to Park City is 95% 75mph freeway. Wide effing open with almost zero traffic. I averaged close to 80mph on that tank. Tank two I averaged closer to 70mph. At 80mph, that is my best mpg ever on that car. At any speed.

These days, I drive 57 miles (the first 5 miles are surface, the rest are 60 mph highways) to work 3 days a week a total of 3 times and one day around town per tank. You can see as the weather has warmed, my mileage has increased from about 24 mpg to about 26 mpg.

Personally, I do better the faster I go. YMMV. Literally.

 

[Eli]

Originally posted by: eos
I'm pretty sure I have posted in every "mpg is better/worse going faster/slower" thread.

1996 Toyota Avalon
3.0L V6
4 speed auto
138k miles

First, visit my mileage page.
Look at the tanks on 2006-07-08. The first one is from Jerome, ID to Park City, UT with a stop in Roy, UT to sleep. Tank two is from Park City to Glenwood Springs, CO. Jerome to Park City is 95% 75mph freeway. Wide effing open with almost zero traffic. I averaged close to 80mph on that tank. Tank two I averaged closer to 70mph. At 80mph, that is my best mpg ever on that car. At any speed.

These days, I drive 57 miles (the first 5 miles are surface, the rest are 60 mph highways) to work 3 days a week a total of 3 times and one day around town per tank. You can see as the weather has warmed, my mileage has increased from about 24 mpg to about 26 mpg.

Personally, I do better the faster I go. YMMV. Literally.

I'm not sure whats more depressing, the fact that you've spent so much time logging MPG data and even making a web page for it...

Or the time line of gas prices that you have illustrated.

 

[AlienCraft]

I generally drive the same route weekly. It is approximately 175 daily with a Friday evening run to the Bay Area from Sac for an extra 220 mi.. The daily run is about 50% hiway and 50% street miles.
During this test, I tried to drive as smoothly around town as possible, (no quick starts, @ Speed limits or below, etc.). The main basic difference was hghway speeds. For one week, I cruised at 72/74 mph with cruise control on, and the next week drove at 65/67 mph with cruise control on.
The first week's driving resulted in an average of 25 mpg.
The next weeks driving resulted in an average of 36 mpg.

These results were derived by calculating the daily MPG and then averaging those results.

 

[Eos]

Originally posted by: AlienCraft
I generally drive the same route weekly. It is approximately 175 daily with a Friday evening run to the Bay Area from Sac for an extra 220 mi.. The daily run is about 50% hiway and 50% street miles.
During this test, I tried to drive as smoothly around town as possible, (no quick starts, @ Speed limits or below, etc.). The main basic difference was hghway speeds. For one week, I cruised at 72/74 mph with cruise control on, and the next week drove at 65/67 mph with cruise control on.
The first week's driving resulted in an average of 25 mpg.
The next weeks driving resulted in an average of 36 mpg.

These results were derived by calculating the daily MPG and then averaging those results.

Looking at my past results, I would say every car is different.

 

[SVT Cobra]

I would assume it depends on the aerodynamics of the car and the gearing.

 

[Eos]

Originally posted by: SVT Cobra
I would assume it depends on the aerodynamics of the car and the gearing.

Now that's a dangerous thought!

You can't take all the facts into consideration...

 

[BoomerD]

Originally posted by: heymrdj
My 04 Expedition gets 18mpg at 55mph and 19.8mpg at 65mph

Wow...Really? That's all? My 05 Expedition gets 25-28 at 70 mph, and 32-35 at 65 MPH...(in my dreams!)
heh-heh...When the truck was new, using the cruise control set at 65, I'd bet about 18-18.5 on relatively flat roads, 16.5 to 17 at 75.

Not a huge difference, but enough to entice me to try to keep my foot out of it except when going long distances on wide-open roads, like through Nebraska, Wyoming, etc.

Because I dislike participating in the local Law encforement department's "Autograph Exchange Program", I try to always stay within 10 MPH of the posted limit...membership usually costs too dammed much!

 

[AlienCraft]

Did an MPG test last Friday on the Sac to Oakland & return run.
Locked the cruise control at 65 and drove like a L.O.L.

2001 Focus SE w/ 2.0L SPI,Auto, A/C off, reg fuel.

Got 36 MPG.

Want to get a tachometer for it, so I can keep the shifting over-revs to a minimum

 

[0roo0roo]

Originally posted by: lein
Recently had a long road trip with a friend in a 96 Volvo (don't remember the model) that had a built in fuel economy sensor. These numbers are not perfect but I guess it can give you a general idea. cruising at 72 mph, the sensor says about 28-29 mpg. At about 78, it drops to around 25-26 mpg. A/C decreases mpg by 1-2, and drafting off an 18-wheeler (probably not a good idea) increases it by 1-2 mpg.

hm in mythbusters drafting even not so close increased the mpg more than that

 

[exdeath]

Originally posted by: RichUK
I never have to worry about fuel costs.

Neither do I, and I don't have to worry about you coming up in my rear view either :laugh: :beer:

 

[mshan]

Bump for an interesting thread.

 

[PricklyPete]

Originally posted by: spidey07
It would totally depend on the car.

My best mileage is around 85 Mph.

Definitely depends on the car. My best mileage happens between 60-70mph (2005 Tacoma V6)

 

[Estrella]

mine actually goes up and then back down as i go faster. If I can hold about 90 I get the manufacturer's highway figure.