I have a 2001 Honda Civic. The EPA city/highway rating is 31/38, According to the sticker on the window. It says that my actual highway mileage should be from 32 to 44 on the highway.
I have many times filled this car and driven 200 miles without stopping on cruise control on a long straight, flat interstate at around 75 mph and have never gotten more than 31 mpg. This, except for the speed, these should be a optimum condition. A friend has a '99 model and gets around 39 or 40. That is a huge difference.
How can this be? I have not discussed this with the Honda dealer yet. Is there some kind of adjustment that can be made? How can these differences exist?
You hit it in your own post - the speed has a ton to do with it. 75 mph has a lot more drag than 55 mph, and will make a huge difference in your gas mileage. I think the testing is done at 55 or maybe 60 mph.
Now if your friend’s figures are also at 75 mph, then I have no idea.
The power needed to go 75 is alot greater than that for 45-50mph (the speed it’s tested at). Actually, it doesn’t even get tested on the road. Highway mileage is really a promising number.
Where are the engineers? I think that it requires six times as much energy to go 70 as it does to go 35? If speed doubles, the energy increases by a higher factor…it doesn’t just double the energy requirement.
…and cruise control is second in efficiency to driving so that your engine maintains a certain rpm and so that your increase load to improve speed gradually, unlike cruise control which holds speed at the cost of fuel.
its the speed. on a trip cross country I saw a huge decrease in MPG on the return because I was going 75-80 as opposed to 60-70 like i did on the way out. I was even carrying less load on the return, but the milage dropped like a stone.
screw it. gas is still “relatively” cheap. drive like hell!
Just another Civic owner chiming in with anecdotal evidence. I have a 98 DX (base model) and usually get ~31-33 around town. On the highway (65-70 without cruise control) I get ~38-40. A couple of years ago on a New Hampshire->Indiana->DC->New Hampshire trip I got average 48 mpg. That was at 65-70 with basically no cargo but me.
31 seems low even at higher speeds and with cruise control.
gigi’s got it. There’s no way around the fact that 31 is abnormally low. And LordVor, I don’t think the ac will cut 5-6mpg.
It is also interesting to note that until I had the civic, I would reguarly get 26mpg on the same trip with my '83 Toyota Corrolla with 180k miles and a funky carbureator!
When driving out to California in my Ford Escort, all high-speed highway driving, I would routinely get around 38 MGP with the air conditioner off, and 27 MPG with the air conditioner on. Granted, other factors also come in, like the fact that if the air is on then it’s hotter out, but the smaller the engine, the bigger the drain the AC is. I do not know how a civic reacts, but it’s not unthinkable that the AC is pulling down your mileage.
I was one of the people that chimed in with charts to show that the same is true for a baseball hit on a hot day, and here I am saying the opposite for cars.
My understanding is that on a hot day, the lower air density causes engine power loss, which has a greater effect on efficiency than just air resistance. Air resistance is less of an issue at low speeds, but engine power/efficiency is an issue at all speeds. Also, on hot days, more accessories are running (A/C, your electric cooling fan, recirc fan)
cool air is better for cars. more O2 per unit volume for combustion, better cooling. i would think that change in air viscosity due to temperature is negligible compared to these things when it comes to efficient operation.
all other things considered between you and your friend’s driving, perhaps there is a breakin period for the car.
So many variables, so little time. My first though is are you sure you’re comparing apples to apples? Do you both have the same type of transmission? Does one car have overhead cams (typically, but not always, dual overhead cam)? Are your engines the same size? (And, what else might have changed between '99 and '01 models?)
But I have to ask: Since when do they tell you BOTH an EPA value and an ACTUAL gas mileage figure? I mean, why bother with an estimated value if they know an ACTUAL figure? I’ve never heard of this…
I have an automatic transmission. I don’t know what he has. Anyhow, I’m told that modern automatics don’t suffer the inefficiencies of older models.
Engines have not changed significantly. Both about 1.7L. I believe both have SOHC. Mine has a VTEC engine (Variable valve Timing. Electronically Controlled) which is supposed to be more efficient and provide more power.
EPA provides a “Highway MPG” which they claim is 38 and a range of 32 to 44.
FCM, see my follow-up post. On my underpowered ford escort, in which turning on the air conditioner basically ate a full gear’s worth of power (had to shirt to 3rd to get the accelleration I’d normally get in forth at a given speed), running the A/C shot my MPG down from the high 30s to the high 20s. On my new Focus, which has a much more powerful engine, I top out around 30 MPG without and about 28 MPG with. I admit that I don’t know the specific effect on a honda civic, but figured that, since it’s designed to get the same sort of gas mileage as the escort, it could have the same effect.
I do think a V-TEC is a DOHC engine, galen. And a V-TEC will burn gass quick if you rev it beyond, say, 6,000 RPM (wherever the second stage kicks in). I’m not sure if it gets better mileage than the non-V-TEC at all, to be honest.
Some more clarifications (it’s obvious you Americans aren’t obsessed with mileage - EUR 1.15 per liter will make you more concious of what your car eats ;)): automatic transmissions may be more efficient than they used to be, but a 1.6 (more likely than a 1.7, which I don’t think Honda makes) with an auto tranny will typically use 10 to 15% more fuel than the identical manual. Not a huge price to pay, but it might explain some of the differences.
Cool air works wonders, especially on underpowered cars. I’m always amazed at how relatively easily my puny 75 BHP Peugeot climbs the French Alps in winter: even at 2,800 meters above sea level, the engine is far more responsive than on the Dutch plains.
- Jinx