Honda Accord Real World MPG

bug4

Is there any consensus concerning at what point fuel economy begins to significantly drop because of high speed?

My new Accord is only running at 2700rpm at 80mph. Interestingly, my old 98 Accord with manual transmission ran 80mph at 3000-3100rpm. Despite this fact, I regularly got 30+mpg at those speeds. As a result, I have been of the impression that speeds of 80-85 mph shouldn't hurt fuel economy too much. But, perhaps I am wrong?

blufz1

Mileage is greatest at the slowest speed in top gear say 40 mph. Don't lug the engine!!!!

robertsmx

Cruising RPM doesn’t tell everything about mileage. A 2.0-liter engine cruising at 3000 rpm may deliver similar mileage as a 3.0-liter engine at 2000 rpm, if throttle opening/load and other parameters are identical. Exceptions aside (Civic 1.8 being one), with larger engines, the gearing gets taller, and effect on fuel economy almost compensated for.

Speed does affect mileage. I have learnt a lot over last 7-8 months, experimenting with my TL. The following represents my observations (fuel economy calculated between tanks, a).
80 mph: 28 mpg
75 mph: 32 mpg
65 mph: 34 mpg

It is almost impossible for me to figure out how much I will average driving between 55-65 mph on freeway over extended period. But, based on trip computer over an extended stretch (not over a tank), the car has indicated 36 mpg around 60 mph.

During long road trips, I watch for my average speed (indicated). Lately, I have been trying to maximize my average speed while maintaining 32 mpg or better. The better hasn’t happened yet, but I have averaged 32.3 mpg at 73 mph (average, point A to point B, no stops included) over a tank. It was part of a 685 mile trip (includes driving around in Houston and Dallas, and slower roads in east Texas, got me an overall average of a little over 29 mpg (interestingly enough, EPA rating on the car is only 18/26 mpg).

In mixed driving, the observed numbers have been so repeatable that if you told me my car was average x mph, I would be fairly accurate in estimating observed mileage without actually measuring it myself. My mixed driving involves 50-50 city/highway split. I would say my average speed on freeways is around 67-68 mph (varies from 60 to 80 during any stretch). City roads range from 30 to 45 mph. It looks like this:
37-38 mph: 26 mpg
34-36 mph: 25 mpg
32-33 mph: 24 mpg
30-32 mph: 23 mpg

These have been observed over full tanks. I have managed 27+ mpg once, but that tank involved more freeway driving and my average speed was 41 mph, so I don’t count it.

Contrary to popular belief, at least in my TL, the best mileage is to be had between 55-70 mph. It is good between 70-75 mph, but seems to taper off quickly approaching 80 mph.

It would be virtually impossible for me to calculate mileage going no faster (or slower) than 45-55 mph, so relying on trip computer, the indication is that I get around 28-29 mpg at those speeds. So, slower isn’t necessarily better. It actually comes down to 26-27 mpg around 35-40 mph. But these readings have potential for big errors since they are indicated over short distances.

In other words, to get the best mileage, 60-70 mph would be it. BTW, the fastest trip I have ever had involved my Accord, with 507 miles covered between Dallas and Memphis including one (5-7 minute stop) at a calculated average speed of 76.5 mph (it would be higher if there wasn’t a 15 mile construction zone right in the middle of Little Rock). I got 32.1 mpg. And EPA’s new rating tells me that the (1998) Accord should get only 27 mpg. :P

80-85 mph does hurt fuel economy, A LOT. Its not the cruising RPM, but the drastically increased drag.

robertsmx

I can't say about the Accord, but I can't have the TL drive in top gear at 40 mph, not even in sport shift mode. It seems to let me use the fifth gear around 41 mph, but refuses to do so going 1 mph slower. Accord's 5AT should behave pretty much the same.

The result, if you drive forever at 40 mph or less, you're never going to use the top gear. Interestingly enough, most of EPA testing cycle involves speed under 40 mph. In fact, it rarely goes past that speed. This logic, I think, plays against Honda when it comes to getting EPA rating. But I also think it makes Honda's numbers more realistic and easier to beat EPA ratings.

bug4

Excellent info! Thanks!

thegraduate

I can't say about the Accord, but I can't have the TL drive in top gear at 40 mph, not even in sport shift mode. It seems to let me use the fifth gear around 41 mph, but refuses to do so going 1 mph slower. Accord's 5AT should behave pretty much the same.

The slowest speed the Accord will shift into 5th (I know this from intentionally trying to get the car to 5th on a 40MPH road I travel) is 42MPH, in the outgoing model anyway (I'd bet $ that the new one is the same). The lowest speed you can maintain in 5th before the car goes back to 4th is 35MPH, but RPMs are right at 1,000 (lugging) at that speed. I'd guess 45-55MPH is best for max mileage, since the engine is a little deeper into its torque band, but still running well under 2k RPM.

Personally, I've gotten over 40MPG more than once with 72-77MPH averages. Around 80 I can maintain 37MPG. Add in two people and 100% A/C use and I get 35MPG at 80MPH.

tankbeans

I'm just curious. Do all the people that consistantly get high 30s low 40s have tremendously long commutes in almost ideal conditions? I've been trying to figure it out. I've been trying to tweak my driving, but I think that my distance traveled each day is just too short to ever break 30. I've broken 30 before, but that was going 150 miles to get my niece. I have an 03 Accord LX Coupe I4.

Also, just curious again, but is the coupe tuned to rev a little differently to get more performance out of it since it could be considered the sport model? I hope these don't sound like dumb questions. People are always telling me that the only dumb question is that which remains unasked.

thegraduate

I'm glad you asked. When I get high-30s or above, the trip is strictly highway/interstate, with little more than a few miles of stop and go (got 38MPG on my last trip to the beach). Few, if any, stops, light loads, and long-ish trips (250mi or more). Around town in my suburban-to-urban commute, I get 28-29MPG.

blufz1

As long as aerodynamic drag increases as a square of the speed,you will not get better mileage going faster than the minium top gear speed.

tallman1

I agree... the 40 mile club is for highway driving only. Even my manual isn't going to give me 40 mpg with many miles of city driving.

Of course, I think I've only had two tanks of gas that were below 30. And I now have 36k miles on my 06 EX-L.

dudleyr

40 mpg is for trips, not most commutes.

The stick Accord goes into 5th at any speed you want.

High speed kills mpg. No accord gets better mpg at 70 than 50 - nobody ever cruises at 50 for an entire tank, so the never see the benefits. My scangauge clearly shows mpg dropping with speed.

Sporin

The low fuel light finally came on today at 394 miles. That works out to ±25 mpg for the first tank straight off the lot. The pump backs up the manual's note that the light come on with 2.8 gal. left in the tank. I pumped in a shade over 15 gallons at the first shutoff. (regular is up to $3.10 today)

Despite being far more "city" driving then we ever do in a regular week that's still better then the Mazda6 was doing.. and I'm still hoping for a 28-30 average once it's broken in and running our regular commute.

Random note, this Accord has the most linear fuel gauge I've ever owned.

Sporin

I run foot/defog most of the winter as well and will be doing that hack asap.

bug4

Does this work for the 08 Accords or was the post for some older model?

thegraduate

This was for the 2003-2007 models. I do no know if it works the same way in the 2008. It's worth a shot though...

dudleyr

I am not sure the battery disconnect would reset this, but it might.

My best guess is that doing the same procedure over again would put things back - like a toggle switch. The problem is that now that I have things just how I want them I am not sure I want to be the guinea pig.

It does seam reasonable that if the car is under warrenty they would reset things.

As far as resale value, as long as you don't push the A/C button after hitting defog the A/C will work as it always did.

Of course I would never reccomend that somebody try it on a rental and report back. :surprise:

mattgg1

dudleyr -

First off, I want to thank you very much for posting this extremely useful process of bypassing the A/C when using the defog/defrost button.

I purchased my Accord over a year ago and have been irritated about the lack of control over the A/C since the first day. My previous car (92 Acura Integra) did not have this annoying feature, and I used the defog setting all of the time. Thankfully, I'm now able to fully utilize my Accord's settings without wastefully running the A/C compressor.

Question for dudley - Where/how did you first discover this "hack"?

Question for everyone else - Why would not NOT take advantage of this "hack"? There are absolutely no drawbacks, you are given full control over your car, and you increase your MPG by not running the A/C!

tankbeans

I tried to do the A/C hack yesterday and I didn't notice that the recirculation light or the A/C light blinked at all. I do, however, notice that when I turn the Defrost on I can hit the A/C button and it will light up. Could it be that someone else has already 'hacked' it? Just wondering. Maybe I misread the directions. I don't know, but I'll probably just leave it as is to avoid damaging the car or something with the electronics unintentionally by hitting a bunch of random buttons.

thegraduate

Without the hack, the A/C button will light up when pressed. Under the hack, when you press defrost, the A/C light comes on (before, the A/C light stays off if off previously when defrost is pressed). You can push the A/C button all you want, but it will not cut off the compressor, just the light.

I don't know what to tell you, maybe print the directions and try again? Make sure you hold the buttons long enough.

bug4

Checked out my 08 Accord -- turns out you don't need the hack. I have full control over the AC compressor via the AC button. AC does automatically turn on when I turn on the windshield defrost button. However, a quick push of the AC button turns off the compressor and is confirmed by a icon on the screen that says "A/C Off." I'm glad Honda addressed this issue on the new models! The only frustrating thing is that I do NOT have A/C control when in automatic climate control mode. As soon as I hit the A/C button when in auto. climate mode, the "auto" climate button goes off and you resume manual temperature control. Of course, I guess there is some argument that it would not be "automatic climate control" if you are manually choosing to disable the system's ability to cool. . . .

bug4

I'm over 3k on the odometer now and I just ran 380 miles of 85 octane gas with 10% ethanol. It was virtually all highway miles - about 50% interstate and 50% two-lane. Drove 80-85 on the interstate and 70-75 on the two-lane. . . lots of up's and down's. Averaged 27.4 mpg. It was cold (20-30degrees) and high elevation (average about 7000 feet) -- I wish I was getting better highway fuel economy. . . Other than one time with a stiff tail wind, I've not broken 30mpg yet. I think I'm averaging about 27mpg. I think my 98 Accord, 4-cyl with MT would have averaged around 30mpg under the same conditions.

thegraduate

That's never been an issue with the Automatic Climate Control models, I believe. We're talking about models from EX Cloth and down, which have manual A/C controls.

thegraduate

It sounds like you have lots of factors working against you. High elevation, interstate speeds that are anything but helpful to getting good mileage (gotta keep things under 75!), lots of hills (which will call for lots of revving at 85MPH), ethanol + winter blend (that would probably count for an at-least 15% drop right there), and pretty cold temps.

All this, combined with a relatively tight engine, and I'd say you ought to be pleased with the mileage.

bug4

Very true -- your right! And, 27 ain't bad -- it just isn't stellar. I'll be eager to see what next summer brings with warmer temps and better grade fuels (and a more worn-in engine). I'm sure hoping I can average around 30-31mpg with highway driving. (Although I drive fast, I am very conservative with the throttle and really try not to let the engine race. Smoooooth is the word . . . . :shades: )

Sporin

I tried the AC hack, but it didn't work on my new LX either. I follow the directions, get the flashing lights and all but when all is said and done and I hit the Defrost button, the AC light does NOT come on (so that I can turn it off).

Thoughts?

thegraduate

My thought is that it works differently on the 08s. The hack we talked about works on the 03-07 Accords without Auto Climate Control. It working on the 08 was not known.

Sporin

Hmmmmmm...... given that the lights flash as before I suspect that the hack still exists but most likely with a slightly different set of button pushes or key positions in the 08.

I'll have to do some digging.

blane

bug4,

In post #1238 you wrote: "I just ran 380 miles of 85 octane gas with 10% ethanol".

Where do you live / drive where you can purchase 85 octane fuel?

Page 260 of the 2008 Accord Sedan Owner's Manual states: "Your vehicle is designed to operate on unleaded gasoline with a pump octane number of 87 or higher. Use of a lower octane gasoline can cause a persistent, heavy, metallic rapping noise that can lead to engine damage."

thegraduate

Using lower octane fuel is common at high elevations.

robertsmx

Yep. IIRC, it was 86+ for my 1998. And during trips to Arizona/Colorado/New Mexico/Utah, 85 is an easy find, while 87 (or 88) is considered premium. But I won't put 85 in my car.

bug4

thegraduate is correct. I live at 6400 feet - every gas station has 85 grade fuel. As I understand it, the metallic rapping mentioned in the manual would happen if the octane level in the fuel was insufficient to keep up with the engine's timing -- particularly in full throttle applications. At higher elevations, there isn't enough O2 in the intake air to take advantage of the higher octane. Of course, I also understand that this means you get worse fuel economy

I might be concerned if I hadn't already driven 4, four cyl. cars with 85 octane to well over 150k miles apiece (2 of them were Honda Accords). I've never had any excessive wear problems with my engines. I sure hope that stays true with my new Accord :confuse:

Sporin

I dug through the manual and found no official "hack" to make the Defrost A/C optional instead of automatic, however, it did say that if you choose FEET the compressor will run but you can hit he AC button twice (on, then off) and it will turn off.

My wife wears contacts so we use the FEET setting a lot in the winter and it will be nice to cut that unnecessary AC compressor during that time.

Wondering if it works the same way for the DEFROST and FEET/DEFROST?

Haven't had a chance to experiment yet.

tankbeans

I apologize, but do you have the 08? Just wondering because I'd like to get the same effect in my 03 since the 'hack' didn't work.

Sporin

Yup, 08 LX sedan.

I'm going to fiddle with the same process on the DEFROST setting in the garage tonight.. might work the same way. I'll post my findings.

ncb81

I just reading this and went to parking lot and tried my Accord and it works fine. mine is 2007 SE V6 hopefully my MPG will get better. I'm getting 23 MPG on my daily commute and my 2004 4runner is getting 20. Thanks to all of you!

Sporin

Almost exactly the same MPG with the second tank, 25.X.

That was a week of our regular commute but we added some pretty chunky snow tires so that higher rolling resistance probably canceled out any higher MPG we would have got from the more highway driving.

This tank also had more then it's share of runs to 6k RPM now that she's broken in a bit.

guru_g

Yup..at higher altitudes lower octane fuel would be sufficient. However, in my experience, I typically get a higher fuel economy at higher altitudes. If you do a bit of freeway driving, the lower density of air at higher elevations (where 85 octane is sold) reduces drag on the car significantly. Since drag accounts for about 40% of the energy expended above 55 mpg, the reduced drag at higher altitudes can be significant. Further, drag force is proportional to the square of the velocity (so speed demons will save even more compared to them driving at sea level).

waltchan

I almost got 40 MPG on highway, but the best I get so far is 37, when driving 55 mph with A/C turned off. It just turned 1K on the odometer. Will it get better in the future once it get more miles.

tankbeans

I'm sure thegrad will tell you that it should get better. Having a 'broken in' engine helps. I can't break 30 because I rarely drive under 70, but anyway good luck and have fun.

thegraduate

You're absolutely right. My first time on a trip, I got between 36 and 37 MPG driving how I always do (Cruise Control on 73-75, no A/C since it was winter). I had less than 3,000 miles on the car. Last winter, in the same conditions, I repeatedly got 38, and sometimes more (a couple of tanks hit or surpassed 40 when the weather got good and winter blends weren't in use but it was still cool enough for no A/C).

Remember winter blend gasoline is going to be hurting you right now. 40 MPG is a rare occurance for me on trips, since conditions have to be just right (and speeds over 70 don't help, and I refuse to drive less than that on a 280 mile trip on the interstates). Anyone can get 35+ though, even at 80MPH speeds (we did it in May going from Bham to Oklahoma City with a friend helping me drive - 600 lbs plus A/C use at 75-80MPH).

I rambled a bit, but as tankbeans said... yes, your mileage should get a little better as the engine loosens up. It won't be a HUGE jump, but 1 MPG average could reasonably be expected based on my experiences.

bug4

Interesting!! I wonder if there is any source out there that has calculated the exact (or estimated) the reduced drag at various elevations. It would be virtually impossible to determine in the real world because higher elevations (particularly 8000+) really only occur in the mountains (where there are lots of other factors affecting fuel economy). Perhaps I should take my Accord to the high Tebetian plains to test fuel economy - - - - - does that sound like an excuse my wife would accept for an exotic vacation?? :P

tankbeans

Hello all-

I just have a quick question. Sometimes when I try to calculate my MPG I have to do so after I've put a few dollars here and a few dollars there and then finally fill it. Is there any way to do this where it won't throw the results off. For instance I can fill then I run low on money and can only put 3 gallons, then later I'll put 2 gallons, but I never actually fill it until the last minute. Is this a bad way of doing it? I feel that my numbers may be off somewhat.

Just curious.

tankbeans

Good luck with that one.

thegraduate

Well, you always have the possibility of a pump reading being off somewhat, but overall, it shouldn't be problem. Two important things to remember to do though:

Write down your gallons pumped each time when you do the little adds

Don't reset the trip odometer until you fill up. When you do finally fill up, use this:

Total Miles Driven before Fill Up / Gallons to Fill Up + Gallons added before complete Fill Up

For example:

550 miles / 2 gallons + 3 gallons + 15 gallons = 550/20 = 27.5 MPG

tankbeans

Thanks I just wanted to be sure. That is what I've been doing but sometimes the numbers seem off. Anyway. The game begins, winter+defrost(I think I hacked it right)+increased weight from snow pack+winter mix=cruddy mileage. I'll be posting periodically so that we can all see if it as that much of an affect.

robertsmx

Partial filling, especially only 2-3 gallons at a time is likely to introduce a big margin for error in your calculations.

blane

Why? That doesn't compute. A gallon is a gallon. Add 'em up and you still get the same total number.

robertsmx

Everytime you fill up, there is a fraction of a gallon extra (or less) that you pump in depending on when the nozzle stops. The extra will be a larger fraction if the fill up is small. If one fills 0.2 gallons more over 1 gallon, that is 20% of the fillup. OTOH, 0.2 gallons more over 14 gallons would be almost negligible.

blane

0.2 gallons = 12.8 ounces. That's almost a pint. I think not.

jaxs1

With temperature expansion and contraction, using different pumps, the car not 100% level, gas in the fuel hose, pump calibration errors etc, it is a waste of time to worry about counting ounces in a tank fill up.
You are not going to be 100% accurate no matter what.