Higher MPG at higher speeds?

[Edina__Monsoon]

New 2018 Touring (sedan) owner. How reliable would you say the MPG indicators are on the Civic? I ask, because, today, when driving home I noticed that the fuel efficiency lights (the "eyebrows") would go solid green if I would accelerate up to and above 80 MPH, but if I went down to the mid 60s to low 70s the "eyebrows" would turn white. It wasn't just those color coded lights -- I think they're called the ambient lights? When I switched the dash display to the MPG setting, it would also indicate a greater MPG at the higher speeds -- even when I was sometimes aggressively accelerating to those higher speeds. Anyone else experience this? I would assume that if I'm hitting the gas pretty hard and rapidly accelerating to a higher speed, my driving would be less fuel efficient. What gives? Maybe it's all physics? I was a liberal arts major. No, I was not in Econ mode, nor was I shifting into "S" at anytime.

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[SoCalCivicSI]

The faster you go the more fuel you use.......it's impossible to get better MPG if you go faster.

 

[Gruber]

The faster you go the more fuel you use.......it's impossible to get better MPG if you go faster.

Generally it's true, except when you go really slow.

But the turbo is a gas-saving device. The engine is more efficient when the turbo is working. When the turbo is not used, all the exhaust gas pressure energy is just wasted.
So until the air resistance really kicks in, there might be a mileage benefit from going a bit faster.

That said, I'm not sure how accurate the onboard mpg computer is at any particular time. It is pretty much verified that it doesn't deviate too much from actual measurements on average. But it is indeed quite surprising how little or apparently no mpg punishment I usually get from the computer for quite "spirited driving" on the freeway.

 

[racer]

Maintaining vehicle speed of 60mph on a level grade takes only about 10-15hp in a modern car. As mentioned, there is a sweet spot of mpg, typically around 45-50mph, where once above that, air and rolling resistence start to have a negative impact. Of course, going up hill vs down hill also has an impact.

I am not familiar with the touring trim and its various dash lights.

I've found the on board computer for fuel economy to be fairly accurate.

 

[gtman]

On my car, I find the trip computer to be a bit optimistic. That said, my MPG sweet spot is about 55 mph on the highway. Above 75 mph the mileage drops off quite a bit.

I also live in a hilly area and that throws things off quite a bit.

 

[raynist]

If I fill up at the same gas station and same pump I find that the MPG indicator is usually within +/- 0.7 mpg from hand calculated.

 

[Rickmeister 48]

In both my civics I've had, when the gas pedal goes down, so does the bar indicating current mpg. And as the bar goes down, the lights go from green to white.
I noticed those lights don't work in sport mode, just stay white.

 

[MuffinMcFluffin]

The faster you go the more fuel you use.......it's impossible to get better MPG if you go faster.

True, but the longer you drive the more fuel you use as well.

 

[caspar21]

funny you say that. i have found the car runs most efficient around 115kph(71mph). thats about where the turbo sits around 0 psi in top gear. this is a higher speed than the 90kph(55mph) of most na cars.

i love turbo.

 

[Aurelleah]

funny you say that. i have found the car runs most efficient around 115kph(71mph). thats about where the turbo sits around 0 psi in top gear. this is a higher speed than the 90kph(55mph) of most na cars.

i love turbo.

My 2.0L has pretty much the same fuel economy between 90 and 110kph (Speed limit vs 20 over for us northern ontarians) from what I've seen, but it's hard to gauge well cause it's so friggin hilly up here. finding a flat stretch where you can just let the car work it and compare is tricky. I can easily get 5.5L/100km tho for sure in the hills-- I actually would like the turbo option just for the newer technology of it, as a nerd thing (I like the idea of the whole "Two engines in one" idea of it). But it's also so great to hear that naturally aspirated engine roar up to vtec when getting up and onto the highway too lol, especially when tuned and with an AEM Intake. I found around 2000-4000rpm it makes sounds really similar to the turbo sounds in the 1.5L from when I test drove it, but with the intake it gets LOUD at 5000+

I think because of the similar weight and aerodynamic properties of both vehicles, and the engineering behind both engines, the fuel efficiency of both vehicles is actually quite similar, despite 500ml difference in displacement. The Turbo makes the power and consumes the fuel of a 2.4L engine when under boost, then cuts back to 1.5L when not boosted, depending on how many hills you have, hillier areas the two would be pretty much the same in fuel economy with the turbo gaining in economy on flat stretches

 

[SoCalCivicSI]

The lowest RPMs in the highest gear will get you the BEST mpg.

 

[VooDuuChild]

That said, I'm not sure how accurate the onboard mpg computer is at any particular time. It is pretty much verified that it doesn't deviate too much from actual measurements on average. But it is indeed quite surprising how little or apparently no mpg punishment I usually get from the computer for quite "spirited driving" on the freeway.

On the Si, at least, the computer MPG shown seems to be within 1 to 2 MPG for most on this thread. I am super impressed with the efficiency of these cars considering their "performance".

https://www.civicx.com/threads/miles-per-gallon-for-the-si.29498/

 

[charleswrivers]

The lowest RPMs in the highest gear will get you the BEST mpg.

X2. I could probably get 50-60 mpg if I could drive 40 mph in 6th everywhere w/o getting run off the road, as that's where the meters settles at. I got 41.X mpgs on a ~600 mile trip back and forth from GA to VA running around 70-75. It was within a few tenths each way.

Hell, I can exceed 30 mpgs in my Odyssey at ~47-48 mph where the torque converter locks in 6th under minimum load. Again... with the getting run off the road.

I've never really seen mpgs improve from the lowest speed in the highest gear you can run, provided you're not lugging. Wind may not be much if a factor early on, but it's force is squared. Considering you're doing double the work (or the same amount in 1/2 the time) it takes 8x the amount of power everytime you double speed. Not a big deal when you're going slow, which is why the difference between 40 and 50 in 6th isn't a big hit... but 70 to 80 is noticable... and once that turbo is spooled and you're feeding the engine forced air, it's got to provide sufficient fueling to not run lean. If you're running fast enough to have the engine loading to be enough to be running boost vice a vacuum and just maintaining speed 1) you'd be breaking the speed limit 2) you're going to be burning a substantial amount more fuel.

I can't say what your display is giving you OP... but once you're in your top gear, so long as you're maintaining speed, I've never seen going faster do anything but lower mpgs. 70 is more efficient than 80... and 60 even more so, though the difference between 60 and 70 would be less than 70 and 80.

 

[civicdabest-foo]

Those eyebrows are only supposed to change colour when accelerating (right??). If they're white, then you're probably pressing on the gas. If you're reasonable with the pedal, they'll be green.

I play with the Fuel app in the dash and those eyebrow lights quite a bit, I suggest this for a fair experiment:

1. Reset Trip Meter A and drive 80 mph for 5 miles and note the average MPG the MPG indicator shows
2. Reset Trip Meter A and drive at the slower speed, and take note of the MPG again.

Your MPG from 1 will probably be around high 30's to low 40's. Your MPG from step 2 should be above 42 mpg, assuming of course you do steps 1 and 2 on level ground and the wind isn't blowing erratically and you're not riding the slipstream of other cars.

Also what were you reading in the Fuel app? The current MPG on the slider animation or the average MPG?

 

[civicdabest-foo]

On the Si, at least, the computer MPG shown seems to be within 1 to 2 MPG for most on this thread. I am super impressed with the efficiency of these cars considering their "performance".

https://www.civicx.com/threads/miles-per-gallon-for-the-si.29498/

I am super impressed with the econo box Touring model, that I can rough around the car in town and get 30 mpg, or get 46 mpg at the highway speed limit of 110 kmph in Canada.

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