Optimal Cruising Speed for MPG

[TyBu]

Yeah, been my experience as well. I get much better mileage on parkways and stuff with 45mph speed limits than I do on the interstate at 75mph. Also, I can't speak for anyone else but the MPG computer tends to be further off when cruising. Like if I do an 80mph 200 mile trip, it'll say 39, but once the math is done it's actually 34. Cruising around town, if the computer says 34, I actually get 34.

My Focus actually got slightly better mileage cruising at 80mph. (But significantly worse mileage at every other speed)

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[Jon Snow]

Is there anywhere where one can even drive around 55 mph on a highway anymore? If I drove 55, I'd get run over, honked at or the one-finger salute.

Don't know how you guys can get over 50 mpg. That's amazing. Best I've ever recorded was around 42 mpg.

Yeah, I've never gotten over 38 on almost all hwy. And in a typical city/hwy mix (mostly flat), I average about 29. Which is far less than advertised, however it is still significantly higher than my previous, smaller, and less powerful car, so I'm OK with it. I do wish the gas tank was maybe 1 gallon larger (my older car got worse mileage, but had a bigger tank so I end up having to fill up about as often).

I feel like unless you're driving 50 mph all downhill and take an eternity to accelerate, there's little chance to achieve ~45+ mpg.

 

[kirkhilles]

Yeah, I've never gotten over 38 on almost all hwy. And in a typical city/hwy mix (mostly flat), I average about 29. Which is far less than advertised, however it is still significantly higher than my previous, smaller, and less powerful car, so I'm OK with it. I do wish the gas tank was maybe 1 gallon larger (my older car got worse mileage, but had a bigger tank so I end up having to fill up about as often).

I feel like unless you're driving 50 mph all downhill and take an eternity to accelerate, there's little chance to achieve ~45+ mpg.

I don't think your MPG is average - maybe off enough to be considered something wrong. I'll easily get 46 MPG on the interstate going up and down hill if traffic is minimal and going 80+ mph. 42 MPG with heavier traffic. Even driving over our mountainous (small) area with traffic lights and some fun acceleration up the hill, still get 35 MPG.

At 29 MPG you are at the near bottom of the Fuelly scale. The most common Average MPG for fill up is 37 MPG.

Might be worth investigating further.

 

[Billy4202]

Yeah, I've never gotten over 38 on almost all hwy. And in a typical city/hwy mix (mostly flat), I average about 29. Which is far less than advertised, however it is still significantly higher than my previous, smaller, and less powerful car, so I'm OK with it. I do wish the gas tank was maybe 1 gallon larger (my older car got worse mileage, but had a bigger tank so I end up having to fill up about as often).

I feel like unless you're driving 50 mph all downhill and take an eternity to accelerate, there's little chance to achieve ~45+ mpg.

If I don't have A/C on, I can usually get upper 40s in my afternoon commute - 70-80MPH, majority highway, and there's no such thing as flat roads here in a valley between two mountain ranges.

My lifetime average (definitely highly skewed towards highway) per the car is 41.0. Try messing with throttle position when highway cruising or turning on ACC to see how it affects your MPG. I've had to experiment a bit.

 

[bigjee]

It's pretty obvious: top gear with the lowest rpm will be the best. Short shift till you get to that spot and leave your ac off and make sure tires are inflated to correct pressure.

 

[Troy Jollimore]

I got a charge when Fifth Gear was doing testing of two cars for mileage. They did it full bore around a track at over 125mph! And the two sedans STILL got 25mpg!!!

 

[RallyeTouring84]

I have averaged 37 MPG (what displays on the dash above the steering wheel, every time i fill up I reset the Trip) but when i look at the trip meter and the current drive MPG I am doing 50-55MPG. most I have EVER gotten out of one tank was 470 and it was on zero. that was without Econ Mode on! full trip from Miami to Orlando and back. Ive been driving with Econ Mode now to see if there is a difference, part of me wants to HAUL ASS and the other half says "patience young padawan" LOL. by far the BEST car i've ever owned gas wise. very impressed.

 

[Erin Tyres]

I don't remember where I got this chart, but I really like it. For best performance, always drive downwind and downhill on a warm day.

 

[NonyaBisness]

I don't remember where I got this chart, but I really like it. For best performance, always drive downwind and downhill on a warm day.

I had to do a drive that invloved a decent amount of low speed constant moving (no red lights or stop signs) and I always find that 35-40 MPH range to be where the Instant MPG stays the highest so I was just gonna post this:

 

[Florida_Frank]

That pretty much exactly matches my experience over the past four years.

 

[Gruber]

I don't remember where I got this chart, but I really like it. For best performance, always drive downwind and downhill on a warm day.

A chart like this is not the best when one is interested in economy. Dollars are not proportional to "gas mileage" (miles/gallon) Dollars are proportional to "fuel consumption" gallons/mile. If you plot gas mileage, it exaggerates the importance of high gas mileage numbers.

Generally, the fuel economy is quite flat between 35 and 70 mph for well engineered modern cars (less flat for big boxy trucks or SUVs). It should be even flatter for turbos. I'm generally not after so minute savings, except for the hypermiling fun. I would save more money by driving less or eating less and cheaper food.

 

[Florida_Frank]

A chart like this is not the best when one is interested in economy. Dollars are not proportional to "gas mileage" (miles/gallon) Dollars are proportional to "fuel consumption" gallons/mile. If you plot gas mileage, it exaggerates the importance of high gas mileage numbers.

Generally, the fuel economy is quite flat between 35 and 70 mph for well engineered modern cars (less flat for big boxy trucks or SUVs). It should be even flatter for turbos. I'm generally not after so minute savings, except for the hypermiling fun. I would save more money by driving less or eating less and cheaper food.

Your statement that "fuel economy is quite flat between 35 and 70 mph" does not apply for this turbo vehicle, apparently. The fuel consumption at 38 mph is 0.0149 gallons per mile while it is 0.0233 gallons per mile at 70 mph. So fuel consumption is 56% higher at 70 mph.

 

[Gruber]

Your statement that "fuel economy is quite flat between 35 and 70 mph" does not apply for this turbo vehicle, apparently. The fuel consumption at 38 mph is 0.0149 gallons per mile while it is 0.0233 gallons per mile at 70 mph. So fuel consumption is 56% higher at 70 mph.

Whether this plot is true is an additional issue. It suggests over 65 mpg when going 35-40 mph. Is this your experience? Are you getting such mileage?
I get over 40 mpg easily anytime on any longer trip without stops. But I can get anywhere near 65 mpg only when going downhill.

 

[Gruber]

Even if the data in this plot were true (they are not) and even if you could always drive 38 mph instead of 70 mph (you can't) how much money would you save?
How much money would an average driver (12,000 miles/year) save, if her gas mileage was 66 mpg instead of 44 mpg (according to this plot)?

She would burn 182 gallons instead of 273 gallons, saving 91 gallons in a year. This is 7.6 gal per month. That's currently less than $20 for me (premium 93 gas only). Since it is impossible to reduce speed to 38 mph, the real savings from driving slower would amount to about one good hamburger meal a month.

 

[longthaitran91]

Since I live in Texas where it is pretty flat for the most part, anywhere from 30-80 mph with cruise control (30-44 cruise control doesn’t function for obvious reasons) on I get 40mpg according to the computer while using the 24 psi of boost tune on my civic. Any slower or faster than those speeds I start losing mpgs. I think you can get still get 30-35mpg at 100mph which is still amazing compared to most other cars

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