Gas Mileage and Ratings

[toxcrusadr]

Yeah it's another thread about my 'new' 2015 Civic EX. Hey it was 2004 last time I acquired a vehicle and that one was 10 years old at the time so I'm understandably excited.

EPA mileage ratings are 29 city/37 hwy, 33 combined.

I'm getting 32 and change on mostly highway driving after a couple of tanks with actual calculations. Kinda disappointed actually. Used to be that you would easily exceed the EPA mileage ratings, but I'm not even achieving them. Did the EPA testing change over the past few years to where it's more realistic and harder to exceed in actual conditions?

I used several tanks worth when I first got it last month and was only looking at the dash readout. Started doing the math when I was not that impressed with the numbers and got the same results.

The Civic has the standard 1.8L 4-cyl with automatic trans (CVT). It has 26,000 miles on it and was very well maintained and runs fine.

Best I've done is 37 for half a tank coming back from Nebraska after Thanksgiving, slightly downhill to MO with a good north tailwind and keeping it to 70-75 mph. Otherwise I haven't seen anything close to that. I should not have to be going downhill with a tailwind just to achieve the highway mileage rating.

Normally I drive 30-35 hwy miles to work with a couple miles at either end of city conditions. I would say 75% of my driving is highway if not more. I do not have a lead foot, I'm a very sedate driver generally. I avoid using the brakes. Granted my commute is hilly in spots. I keep it to 75 on the flats and downhills and 65-70 on the uphills. I turn off the cruise so the car doesn't shift down and floor it on steep hills.

I looked at DOE's website and there are 7 reports from drivers who estimated their % city vs. highway and gave an average mpg. Those ranged from 24-39 with a combined average 30.9. Not a big sample but a couple mpg below EPA's combined of 33.

Saw the usual cautions about temperature, driving habits, tire inflation, initial breakin (not a factor at 26k), drivers having fun with a new car, all that, and none of those usual things should be causing me low mpg. I just thought I'd be getting at least 10-15% higher mileage out of the car, if not more.

Thoughts?

 

[Yamaki]

So did you start your tests recently? I've noticed quite the drop in MPG in my gas powered vehicles as fall and winter approaches as the fuel supply transitions to winter blend fuels.

Winter gas is more volatile and evaporates more quickly due to higher ethanol, so it is ideal for it is used in the colder air of winter. In terms of gas mileage, you get better mileage on summer blends than winter blends because the summer blend gasoline has a greater energy value than winter blend. The ethanol content displaces a small percentage of "real" gasoline so you actually end up with less usable fuel.

Also, colder weather weather does have a significant impact on fuel economy. If you really want to dig into it, here's link to the US DOE study results on cold weather impacts on fuel economy:

https://www.fueleconomy.gov/feg/coldweather.shtml

 

[Hajidub]

Tox, realize that a ton of states have started with the "winter" gas (high ethanol). Also on your long trip did you happen to utilize the ECON button (lower left)? When acceleration isn't required it's a great feature that will exceed the EPA ratings.

 

[TPettenati]

Try your trip at 65 MPH max.

https://www.consumerreports.org/cro/news/2009/09/tested-speed-vs-fuel-economy/index.htm

 

[noogies]

Try your trip at 65 MPH max.

But stay outta my way!

 

[analoge4ever]

I drive a 2nd Gen Chevy Volt. Average mpg over life of car was 101 mpg last I checked.

 

[MacNoob]

Go hit fuelly.com and look up mileage for similar cars. You can get a chart that shows average MPG across the whole reporting population and see where you are on the bell curve.

 

[quaddriver]

back her down. with OD and flat EFI curves, 55 is a waste, but 65 is a sweet spot, given that since wind resistance increases with the *SQUARE* of speed, over 65 it becomes very significant.

also, pay attention to alky gas. E10 is 10% of something that aint exactly fuel (besides being an enormous boondoggle and waste of resources and money for false reasons - but thats another rant for another day)

 

[gadget73]

The window sticker for my 86 Towncar claims 27 mpg on the highway. Maybe if you hooked it to a truck and towed it downhill you'd get that. 18 is what I usually get. Of course thats ~70 mph with what amounts to a brick-shaped couch on wheels that was built in an era with a 55 mph national speed limit that also burned real honest to goodness gasoline.

 

[toxcrusadr]

Answering a few of the above questions and comments:

I just got the car Nov. 10. I casually watched the dash mpg readout but have only actually calculated it for 2 tankfuls, both of which are my typical driving. 32.1 and 32.6.

I have not really used the Econ button but I know it causes the car to shift up sooner so it will accelerate more slowly but with greater efficiency. I will try it one of these days, but as I said I'm a pretty sedate driver. I have not used the S setting on the shifter either - S is for sport and does the exact opposite!

I would have thought that since almost all gas is 10% ethanol now, that the EPA ratings are using the fuel everyone uses.

It has not been particularly cold, in fact, unseasonably warm here. So on the one hand I don't have extreme cold reducing the mileage, but on the other hand higher temps could lead to increased evaporation. But it's only been in the 50s-70s for highs, not summer-like.

Ethanol certainly is fuel, although I fully agree (as a chemist) it does not give off the kcals per gram that gasoline would simply because it's already partially oxidized. I am not even sure I can get no-ethanol gas in Missouri. I think there's a state law mandating 10%, probably the corn farmers.

Wiki indicates that gasoline gallon equivalents (i.e. amount required to get the same total energy) for 'base' conventional gasoline, conventional winter gasoline, and E10 are 1.000, 1.013 and 1.019. So winter gas and E10 are about the same and are within 2% of straight gasoline. https://en.wikipedia.org/wiki/Gasoline_gallon_equivalent Obviously E85 is going to be considerably lower in energy but at 10% it's hardly noticeable. I don't know what they use in the winter here - it may be winter blend with the ethanol superimposed on top, and that would be over 4%. But I bet it is not that simple.

65 mph, I did plan to try that as I'm aware of the exponential increase in drag at higher speeds. I would need to do it for a whole tank, and that's 4-5 trips to work.

Thanks for the fuelly.com link Macnoob. I will check it out.

 

[dosmalo]

back her down. with OD and flat EFI curves, 55 is a waste, but 65 is a sweet spot, given that since wind resistance increases with the *SQUARE* of speed, over 65 it becomes very significant.

also, pay attention to alky gas. E10 is 10% of something that aint exactly fuel (besides being an enormous boondoggle and waste of resources and money for false reasons - but thats another rant for another day)

Agree with quad all the way around his post. 65 always felt like the sweet spot for me especially back in the day of the mandated 55.
But - I think there is a seasonal blend, and an ethanol blend and then E10, at least in my state that's what I see. OK is one of (and has been for years) last remaining states where you can buy 'real 100% gasoline' at quite a few places and it is always promoted heavily as being such. I see stores or stations where the pumps are labeled as 100% gasoline, blended and E10, with E10 always having a significant lower price up on the sign to pull you in.
Also but - I will pass this along from back in the day - I worked for a gasoline pipeline terminal and was still working when the EPA 'blended' rules went into effect and gasoline was blended not only for seasonal reasons but also for geographical reason and it had nothing to do with alcohol. It may now but initially it did not.
Regardless of who's branded gasoline was trucked out, it all came out of the same pipeline and we never, ever handled alcohol blended fuels.
Also, tox may be experiencing what I did when I tried alcohol blended gasoline and that was a phenomenon where my trip computer told me I was getting the same mileage but the gas gauge told a bleaker tale. The only way I could explain it was that alcohol blend in the tank was evaporating faster than 100% gasoline did.
It was very noticeable and for that reason in addition to all of the alleged negative effects on the fuel system made me shy away from any alcohol blends.
But as I said above, I'm still able to find 100% gasoline at more places than usual.

 

[toxcrusadr]

Fuelly.com is great! There are 10,741 Civics that have reported data. For the total - and the 565 that are 1.8L sedans - the average MPG reported in both cases is about 32-33 mpg. So I'm right in the average, but still disappointed that I don't get 35 or more on the highway.

 

[toxcrusadr]

Ethanol itself has a vapor pressure about in the same range as the lighter hydrocarbons in gasoline (under the same pressure and temp conditions), but since it's a complex mixture, it's not that easy to predict how much faster it would evaporate. Product tests appear to show that E10 does lose weight to evaporation faster than pure gasoline, and the vapors are enriched in ethanol (13% vs. 10% in the liquid, in one study I saw). So you're right, it can evaporate a bit faster. Whether that's fast enough to actually affect mileage, I don't know yet.

Now I'm going to have to research the EPA fuel efficiency test protocol and see what it actually requires for fuel. Down the rabbit hole we go!

Note, I've used E10 here in MO for all my cars and trucks for years, and I don't have problems with the fuel systems. I also use it in my mowers and for all I know the 91-93 octane I use in the chainsaws is E10 too. They all work fine. Worst problem I had was a ca. 2014 Sears mower that would quit, and it turned out they were too cheap to put any kind of a fuel filter on it. Installed a $1.99 inline filter and my troubles vanished.

 

[matteos]

Lots of things at play here. Tire inflation, the way you drive, traffic, elevation... even the temperature (Cold air means more of it in the cylinders... you'll even get more gasoline in your tank if you pump when it's cold).

But mostly it's how you drive and driving conditions. I get about 15mpg driving down the 10 freeway at 5mph which is what I do everyday. But on the freeway with no traffic I'll get 32mpg.

 

[quaddriver]

Ethanol certainly is fuel,
.

ethanol is a 'fuel' in the strict sense that it can oxidize and produce heat, if we were burning in a garbage pit.....

but for a gasoline engine its certainly a lousy fuel.

granted many things can burn in there - part of my HS research project way back in EC2 (energy crisis 2) was using the ubiquitous B&S motor to test different fuels and measure output (used a generator, electrical, when it tops out = end of usuable power etc etc) and heck, I had em running on coleman fuel and lighter fluid....and everything in between.

but in a feedback motor (such as pretty much all of ours reading this, save my 78 Regency) NOT using a carb, the presence of O2 liberated (as you know the first reaction in a blended fuel burn is to liberate the oxygen in the ethy/methy molecule) causes the E/PCM to restrict (if equipped) air injection to keep the crosscount numbers up. when it detects that has failed a moment ago, it is not violating the HC standard, but is the NOx standard,..... so it long term trims the mix slightly rich and that and that alone is the first order effect on mileage. at highway speeds at highway rpms, the power loss from E10 is like an extra suitcase in the trunk (aim small, miss small engineering practices in use), the real mpg loss is due to emission regs and compliance thereof.

Plus! as an added bonus, in the heat of combustion, and the use of rhodium to mitigate NOx emissions, the car will produce a good bit of O3. Good for us if you run the car at 100,000 ft+ altitude. Bad if you do it at ground level.

now if you have one of those flexy fuel motors, they adapt knowing full well that the power loss at cruise is jack and DO NOT enrichen the mix and hence, the flex motors on even E85 - dont score horribly. plus the flex fuel motors dont dissolve half the fuel system just sitting there. (I fear for the life of my regency....)

 

[62caddy]

... you'll even get more gasoline in your tank if you pump when it's cold).

How does refueling during cold weather net any more fuel?

 

[quaddriver]

Ethanol itself has a vapor pressure about in the same range as the lighter hydrocarbons in gasoline (under the same pressure and temp conditions), but since it's a complex mixture, it's not that easy to predict how much faster it would evaporate. Product tests appear to show that E10 does lose weight to evaporation faster than pure gasoline, and the vapors are enriched in ethanol (13% vs. 10% in the liquid, in one study I saw). So you're right, it can evaporate a bit faster.

if your car is EFI[1] and post 85/86ish, it should not suffer any evaporation at all....the EVAP system and vapor storage should get that down to damn near zero, unless you park in sunlight in the desert and you exceed the pressure rating of the fuel cap, installed to prevent it from becoming a rather efficient bomb...

notes:
[1] - try as they might, when subjected to heat soak, the throttle shaft seals on the carbs have to leak and nothing smells sweeter than a 4bbl being cooked from under hood heat....

 

[dosmalo]

I do recall that before the ethanol craze there was (is, maybe?) the precursor blending agent MTBE and I had lots of 1st hand experience with that stuff.
It will literally evaporate before your eyes basically like ether or the 'E' in MTBE.

 

[quaddriver]

How does refueling during cold weather net any more fuel?

im not sure it does, to keep diesel from gelling, they stir the tanks and by accident found that you can put about 10% wbv (weight by volume) air in diesel - meaning you pay up to 10% for something you dont get, yet the pump ticker keeps reading. those miserable 500,000 miles I put on diesel jettas taught me to be VERY distrusting. not sure if gas has the same ability as diesel, but would not put it past them to try...

 

[quaddriver]

I do recall that before the ethanol craze there was (is, maybe?) the precursor blending agent MTBE and I had lots of 1st hand experience with that stuff.
It will literally evaporate before your eyes basically like ether or the 'E' in MTBE.

plus its water soluable, causes cancer, and now flows like underground rivers in all of california!