Can't consistently reach 30 MPG
#1
08-31-2010 | 10:53 PM
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From: Cumming, GA
Can't consistently reach 30 MPG
I bought a new 2010 Fit (base model, automatic) about a month ago. Overall I'm quite happy with it, but I don't seem to be achieving the "official" figure of 30 MPG. On my first four tanks of gas, I've been averaging between 26.5 and 28.5 MPG according to the trip computer.
Most of my driving has been around town, and in addition to stoplights and stop signs there are also a lot of hills. How much does this affect the mileage? I've tried to use a light touch on the gas pedal and to coast as much as possible, but I still can't get to 30 MPG throughout a full tank. I can do about 35 MPG on the local limited-access highway, but this all gets lost during town driving. Due to weather conditions, I have been running A/C 100% of the time.
When going up a steep hill, is it best to creep upward slowly (giving only as much gas as needed to climb it) or to give it more gas and get to the top quickly?
I live in north Georgia, and my county is listed on the EPA website as having reformulated gasoline. How much impact does that have on MPG?
Would increasing the stock tire pressures to something like 40 front / 36 back (or even 45/40) help with mileage? Would doing so compromise safety or make the tires wear faster?
Any other suggestions? The current mileage isn't terrible (it's much better than I got with my old '02 Focus) but other people seem to be doing much better and I'd like to figure out why my results aren't measuring up.
Most of my driving has been around town, and in addition to stoplights and stop signs there are also a lot of hills. How much does this affect the mileage? I've tried to use a light touch on the gas pedal and to coast as much as possible, but I still can't get to 30 MPG throughout a full tank. I can do about 35 MPG on the local limited-access highway, but this all gets lost during town driving. Due to weather conditions, I have been running A/C 100% of the time.
When going up a steep hill, is it best to creep upward slowly (giving only as much gas as needed to climb it) or to give it more gas and get to the top quickly?
I live in north Georgia, and my county is listed on the EPA website as having reformulated gasoline. How much impact does that have on MPG?
Would increasing the stock tire pressures to something like 40 front / 36 back (or even 45/40) help with mileage? Would doing so compromise safety or make the tires wear faster?
Any other suggestions? The current mileage isn't terrible (it's much better than I got with my old '02 Focus) but other people seem to be doing much better and I'd like to figure out why my results aren't measuring up.
#2
08-31-2010 | 11:56 PM
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Joined: Oct 2007
Posts: 2,304
From: Illinois
The AC uses the most gas. I am familiar with that part of GA. Reformulated gas lowers gas mileage about 3 percent, but running the AC uses 20-30 percent more gas below 50 mph. The mileage is not that bad for that type of driving. You need to take it out for a ride on the highway and see if mpg go up. I averaged 40 highway in my Fit. I keep my pressure around 38 psi all 4 tires.
#3
09-01-2010 | 12:12 AM
I also live in Georgia (Duluth) with a 2010 fit (sport) that I bought about a month ago and have been averaging between 28 and 31 mpg. I drive to Atlanta from Duluth for work about 4 times a week and the rest of the time around the city. My preferred method for hills is to gas it to get the top then coast to the bottom instead of going slowly up it, probably just because I like to drive "spiritedly" lol. I also use the AC all the time, but mostly on the 1 setting and only the 2 when I first get in the car. I guess maybe the combination of reforumlated gas and ac all the time is whats hurting you?
#4
09-01-2010 | 12:37 AM
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Joined: Oct 2007
Posts: 2,304
From: Illinois
My preferred method for hills is to gas it to get the top then coast to the bottom instead of going slowly up it, probably just because I like to drive "spiritedly" lol. I also use the AC all the time, but mostly on the 1 setting and only the 2 when I first get in the car. I guess maybe the combination of reforumlated gas and ac all the time is whats hurting you?
#7
09-01-2010 | 04:22 PM
I get an avg of 32mpg w/moderate use of a/c, with mild hypermiling techniques only on the highway. i drive like a mad man on roid&crack on surface/local streets.
ive noticed with heavy hypermiling on surface+highway nets an avg of 38+ mpg combined. that would mean im getting either low 30's on surface and mid to high 40's on the highway(these numbers are all calculated using gallons of fuel consumed divided by the miles driven)
its all due to your city driving, it will kill good mpg when you drive only in stop and go and stoplight traffic.
get on the highway and experience the mpg bliss.
ive even had a time i got 45mpg driving down from mammoth mountain(ski resort, high mtn in central california) coasting in 5th gear with little to no throttle input going 80mph.
ive noticed with heavy hypermiling on surface+highway nets an avg of 38+ mpg combined. that would mean im getting either low 30's on surface and mid to high 40's on the highway(these numbers are all calculated using gallons of fuel consumed divided by the miles driven)
its all due to your city driving, it will kill good mpg when you drive only in stop and go and stoplight traffic.
get on the highway and experience the mpg bliss.
ive even had a time i got 45mpg driving down from mammoth mountain(ski resort, high mtn in central california) coasting in 5th gear with little to no throttle input going 80mph.
Last edited by JJIN; 09-01-2010 at 04:27 PM.
#8
09-01-2010 | 05:45 PM
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Joined: Jul 2010
Posts: 8
From: Austin, Texas
I used to get around 27 mpg with mixed city and highway. Today I set the trip meter to zero and drove a 18 mile(9 highway + 9 city) with normal traffic. I got over 40 mpg with highway and averaged 36 mpg with mixed road.
I think the driving style mattered a lot. I used the aforementioned "pulse and glide" technique. While you drive, if you switch to the mpg display on the indicator, you'll actually see that when you speed up it requires a lot of gas, less than 10mpg. when you let it coast, the instant mpg at the time is from 40-80. So this means that the more you brake on the car, the more you need to accelarate later, the more gas you use. so driving smoothly helps a lot on the mpgs. but don't get distracted from the indicator. drive safely.
another thing is that when you coast at a certain speed you'll slowed down gradually, you can tap gently on the gas and give it a little push and then coast again.
I think the driving style mattered a lot. I used the aforementioned "pulse and glide" technique. While you drive, if you switch to the mpg display on the indicator, you'll actually see that when you speed up it requires a lot of gas, less than 10mpg. when you let it coast, the instant mpg at the time is from 40-80. So this means that the more you brake on the car, the more you need to accelarate later, the more gas you use. so driving smoothly helps a lot on the mpgs. but don't get distracted from the indicator. drive safely.
another thing is that when you coast at a certain speed you'll slowed down gradually, you can tap gently on the gas and give it a little push and then coast again.
#9
09-01-2010 | 08:37 PM
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Joined: Aug 2009
Posts: 3,661
From: Georgia
The AC uses the most gas. I am familiar with that part of GA. Reformulated gas lowers gas mileage about 3 percent, but running the AC uses 20-30 percent more gas below 50 mph. The mileage is not that bad for that type of driving. You need to take it out for a ride on the highway and see if mpg go up. I averaged 40 highway in my Fit. I keep my pressure around 38 psi all 4 tires.
20-30% more gas than what?
If the A/C diverts 10% of the energy from the wheels to the A/C compressor at highway speed that's equivalent to about 3mpg. I think it's a bit less based on personal experience.
The A/C compressor runs more at city speeds than highway so mileage will suffer a little more. Maybe even 20-30% more (20-30% of 3mpg is about 1mpg less per gallon.)
Josh G, you're right on the money for city driving, doing better than the EPA estimate of 28 city for your mostly city driving. I don't know what "official" figure of 30 you're referring to (31mpg combined?).
My 09 base auto in Atlanta (about 70% interstate I75/I285 50 miles RT) gets 32mpg summer and about 34mpg winter over the same commute. Driving exclusively on the highway it goes up. Driving exclusively in the city it goes down.
#10
09-01-2010 | 10:24 PM
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Joined: Oct 2007
Posts: 2,304
From: Illinois
At Idle it uses .20 gallon an hour so the Fit can idle for 5 hours using 1 gallon of fuel no load. Its short trips not city driving that gives the worst mileage. I drove the city home and took an extra 30 minutes and got 40 plus mpg with some AC usage at lights. If you have a scan gauge you would see at idle 50 percent more fuel being used. Goes to .30 gph. Any time there is a load (lights,AC and even brakes)the ecu will put more fuel in so you have torque available to move the car. At speeds above 50 mph I would agree with you Steve244 that it might be a 1-3 mpg loss. I was stating that the AC usage in Josh G is the only thing he can change. I know going up hill uses a lot of gas but going down hill uses none if you time it right.
Last edited by SilverBullet; 09-01-2010 at 10:54 PM.
#11
09-01-2010 | 11:43 PM
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Joined: Aug 2009
Posts: 3,661
From: Georgia
At Idle it uses .20 gallon an hour so the Fit can idle for 5 hours using 1 gallon of fuel. Its short trips not city driving that gives the worst mileage. I drove the city home and took an extra 30 minutes and got 40 plus mpg with some AC usage at lights. If you have a scan gauge you would see at idle 50 percent more fuel being used. Goes to .30 gph. Any time there is a load (lights,AC and even brakes)the ecu will put more fuel in so you have torque available to move the car. At speeds above 50 mph I would agree with you Steve244 that it might be a 1-3 mpg loss. I was stating that the AC usage in Josh G is the only thing he can change. I know going up hill uses a lot of gas but going down hill uses none if you time it right.
Josh has said he's getting 26.5-28.5 city driving using the A/C. He is not going to get 39mpg in the city by turning off the A/C. Realistically he might get 28-30mpg (about a 5% increase in mpg).
Also your description of the ECU increasing torque when using the A/C and/or lights is inaccurate. It increases idle speed about 250RPM to turn the alternator faster and keep from lugging under the A/C compressor load. The ECU does this by opening the throttle slightly. On cars without drive-by-wire it's done by means of an idle air control (IAC) valve. Anything above idle isn't effected (except the ECU will turn off the A/C compressor during hard acceleration).
#12
09-02-2010 | 12:20 AM
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Joined: Oct 2007
Posts: 2,304
From: Illinois
What you're saying (I think) is using the A/C during stop and go city driving decreases mpg another 30% over not using the A/C. This isn't accurate. That would be about 8.4mpg less (19.6mpg instead of 28 for the Fit) just from running the A/C. If anyone experiences this I'd like to hear from them. While some people are complaining about getting less than 20mpg, this is not normal (way outside the curve); I suspect they have interesting driving habits.
I agree about driving habits, I always get more mpg that Honda says and I do drive aggressively on the highway. If Honda average is 32 mpg, 20 percent loss because AC is on is 26-28mpg. I drove the back roads with lots of lights and still got around 40 mpg. I also told him to take a trip on a highway to get a average of mpg on highway mixed driving.
Josh has said he's getting 26.5-28.5 city driving using the A/C. He is not going to get 39mpg in the city by turning off the A/C. Realistically he might get 28-30mpg (about a 5% increase in mpg).
No not 39, but he should get 31-32 mpg. Short trips with multi start up of the motor will hurt mileage. If his commute was near an hour his mpg should go up and dont know if he goes out for lunch or idles the car in the parking lot to listen to the radio. I see people race home for lunch and complain about mileage.
Also your description of the ECU increasing torque when using the A/C and/or lights is inaccurate. It increases idle speed about 250RPM to turn the alternator faster and keep from lugging under the A/C compressor load. The ECU does this by opening the throttle slightly. On cars without drive-by-wire it's done by means of an idle air control (IAC) valve. Anything above idle isn't effected (except the ECU will turn off the A/C compressor during hard acceleration).
I agree about driving habits, I always get more mpg that Honda says and I do drive aggressively on the highway. If Honda average is 32 mpg, 20 percent loss because AC is on is 26-28mpg. I drove the back roads with lots of lights and still got around 40 mpg. I also told him to take a trip on a highway to get a average of mpg on highway mixed driving.
Josh has said he's getting 26.5-28.5 city driving using the A/C. He is not going to get 39mpg in the city by turning off the A/C. Realistically he might get 28-30mpg (about a 5% increase in mpg).
No not 39, but he should get 31-32 mpg. Short trips with multi start up of the motor will hurt mileage. If his commute was near an hour his mpg should go up and dont know if he goes out for lunch or idles the car in the parking lot to listen to the radio. I see people race home for lunch and complain about mileage.
Also your description of the ECU increasing torque when using the A/C and/or lights is inaccurate. It increases idle speed about 250RPM to turn the alternator faster and keep from lugging under the A/C compressor load. The ECU does this by opening the throttle slightly. On cars without drive-by-wire it's done by means of an idle air control (IAC) valve. Anything above idle isn't effected (except the ECU will turn off the A/C compressor during hard acceleration).
Honda idles at 700 rpm no load so if idle goes up to 900 rpm with load thats a 30 percent increase.
More air needs more fuel, if no more fuel was added it would die or overheat because it would be running to lean. Ive seen this on the scan gauge. The ecu doesn't know what your next move is so it has to add fuel to have torque available to move the car with out stumbling and to power the acc. Honda adjusts the idle with the timing so it adds air and fuel and controls it with the timing. You also have to take in consideration humidity, temp, and barometric pressures. All those have an effect on how much fuel is added.
I guess it depends on which way you do the math, but the AC uses more fuel especially below 50 mph. Ive seen websites that said 35 mph but then say highway speeds so I dont want to argue that point.
#13
09-02-2010 | 10:15 AM
I dont know about you guys, but I had to readapt to get to the 30 mark (and with an AT) Im not as agressive, although when I have to be on time, i have to be on time 
pure city, im at 28-29 with moderate A/C (its on during burning hours, windows at night)
Highway ive hit 37+ using cruise control, and doing the slow roll on uphills (i was always embarrased to be on the truck/bus lane
)
pure city, im at 28-29 with moderate A/C (its on during burning hours, windows at night)
Highway ive hit 37+ using cruise control, and doing the slow roll on uphills (i was always embarrased to be on the truck/bus lane
)
#14
09-02-2010 | 10:26 AM
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Joined: Aug 2009
Posts: 3,661
From: Georgia
If your point is using A/C reduces mpg, this is true. But it's only a couple MPG. How many mpg do you think yours uses above what would normally be consumed at city speeds?
Last edited by Steve244; 09-02-2010 at 10:28 AM.
#16
09-02-2010 | 09:31 PM
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From: Cumming, GA
I appreciate all the answers. It sounds like what I'm getting is normal given the driving conditions, use of A/C, and transmission. Some people said that the automatic gets worse mileage than the stick shift, though EPA tests seem to show the opposite (28/35 auto, 27/33 stick). Apparently these results don't reflect the average driver, at least on this board. It's a moot point in any case, since I don't know how to drive a manual transmission vehicle.
I'll keep an eye on my mileage as the fall comes around and I have an opportunity to use less A/C. Perhaps that will help. So far I have not been on any long highway trips, so if I do so that will also give me a chance to monitor how it does.
I'll keep an eye on my mileage as the fall comes around and I have an opportunity to use less A/C. Perhaps that will help. So far I have not been on any long highway trips, so if I do so that will also give me a chance to monitor how it does.
#18
09-03-2010 | 05:52 PM
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Joined: Feb 2007
Posts: 1,244
From: Colorado Springs, CO
Mine is an '07 but your numbers sound about right. Just depends on exactly how much stop and go + hills you have. I get around 29-30mpg on my daily commute driving conservatively, if I push it, that drops to 26-27. But during my road trips from California to Colorado 39-40mpg easy. Probably more if it wasn't for the mountains. 
