Unusually Poor Gas Mileage

[SonicBoomhauer]

Howdy y'all,

I just picked up my 2013 Sonic LT 1.4 six speed two weeks ago. I got it with 7,000 miles on the clock. My question comes in regards to the fuel economy.

I've driven the car about 1600 miles since I bought it, and I have only averaged 28.9 mpg. Now granted, some of that was in pretty brutally cold weather, but it was 85% highway driving. I've experimented with different fuels, trying to avoid ethanol (night unto impossible in the midwest unless you get premium, which I did for one fill up, and have been using STP each fill up to compensate for the ethanol) and the best I've gotten was 30.9 mpg.

Is this absurdly low mileage because the engine is still in the break-in process, because of the unusually cold weather, or what's the issue here?

I also just replaced the stock air filter with a K&N and the weather is *finally* warming up, we'll see if that makes a difference... but any thoughts on why I've been getting such ridiculously bad mileage?

 

[Scot]

Right now, with the cold temps and highway driving while running 93 octane, I get about 32 mpg driving 75 mph. This is down from 38 - 39 mpg when it's warm outside. Also, for reference, I have a little over 10K miles on my car. 1.4L & MT.

 

[ahtoxa]

How long are the highway drives? How long is the total distance traveled during your one-way commutes?

 

[Z71]

Did you use the cruise control? Were you in the top (sixth) gear most of the time?

I would try running the car on 93 octane for a while. I find recommendations to operate turbocharged engines on 87 octane rather strange. Lower octane may negatively affect your fuel economy due to the ECU retarding the ignition timing more.

Is the turbo operating properly? When you have a turbo malfunction, your mileage will suffer.

 

[Gary Grist]

Poor mileage

With the 6 sp MT it is very easy to wind out the gearing; particularly in first gear. That uses a lot of gas. I would advise shifting out of first very quickly, don't wind it out. Go thru the other gears quickly as well, shifting before the 'shift' light comes on and keeping the tach below 2000 rpm until you get to 6th. For highway driving, stay below 65 mph. The faster you go, the wind resistance increases exponentially. Air is denser at low temperatures during the winter, so this will reduce your mileage even more. Put 38-40 lb cold pressure in your tires. This alone can add 1-2 mpg on the highway. On my RS 1.4 MT, I get 40 mpg for pure highway miles and 34 for combined with 87 octane w/ 10% ETOH. A little less duirng cold spells.

 

[Nimda]

With the 6 sp MT it is very easy to wind out the gearing; particularly in first gear. That uses a lot of gas. I would advise shifting out of first very quickly, don't wind it out. Go thru the other gears quickly as well, shifting before the 'shift' light comes on and keeping the tach below 2000 rpm until you get to 6th. For highway driving, stay below 65 mph. The faster you go, the wind resistance increases exponentially. Air is denser at low temperatures during the winter, so this will reduce your mileage even more. Put 38-40 lb cold pressure in your tires. This alone can add 1-2 mpg on the highway. On my RS 1.4 MT, I get 40 mpg for pure highway miles and 34 for combined with 87 octane w/ 10% ETOH. A little less duirng cold spells.

Shifting before 2000 RPMs or before the shift light? I don't know how some of you guys do it, lol. If it were up the shift indicator in my 5MT it would tell me to shift into 5th gear at 30mph. I love RPMs too much and shift consistently at about 3500 or so managing 33mpg on a regular basis.

 

[ShadowRS]

Most likely just crappy cold weather conditions or driving conditions. Check your tire pressure or something.

 

[Gsrdude]

2nd GM I had in a row that doesn't even come close to claimed mpg. Oh well

 

[KartRacer]

You can get really great mileage if you push the dxxx thing. Gas mileage varies, extreme cold sucks fuel, a/c and hot weather suck fuel, driving to have a little fun sucks fuel. Quit complaining about great fuel economy which will vary from 25 to 36 in an RS and much better in non non RS due to gearing.

 

[ahtoxa]

With the 6 sp MT it is very easy to wind out the gearing; particularly in first gear. That uses a lot of gas. I would advise shifting out of first very quickly, don't wind it out. Go thru the other gears quickly as well, shifting before the 'shift' light comes on and keeping the tach below 2000 rpm until you get to 6th. For highway driving, stay below 65 mph. The faster you go, the wind resistance increases exponentially. Air is denser at low temperatures during the winter, so this will reduce your mileage even more. Put 38-40 lb cold pressure in your tires. This alone can add 1-2 mpg on the highway. On my RS 1.4 MT, I get 40 mpg for pure highway miles and 34 for combined with 87 octane w/ 10% ETOH. A little less duirng cold spells.

This isn't always the case. I've found that accelerating briskly to get to the optimal engine speed in top gear is usually more fuel efficient. You're not flogging it, but you're not wasting time slowly climbing the revs because you're in too high a gear because you're shifting too early.

Either accelerating to that optimal efficiency too fast or too slow will cause more wasted energy than necessary.

 

[Nimda]

this isn't always the case. I've found that accelerating briskly to get to the optimal engine speed in top gear is usually more fuel efficient. You're not flogging it, but you're not wasting time slowly climbing the revs because you're in too high a gear because you're shifting too early.

Either accelerating to that optimal efficiency too fast or too slow will cause more wasted energy than necessary.

this

 

[KartRacer]

Sorry for being a little pissy on previous post. I am soooo pleased with all the money I am saving on fuel while having a great time driving my RS.

 

[SonicBoomhauer]

I've been running it with the tires aired up to 39 PSI, try to spend very little time in 1st gear (unless I'm showing off ) and have been using my cruise at every opportunity. I've been doing a LOT of interstate/highway driving, setting my cruise at 75 even on the interstate and at 65 on the secondary highways.

I definitely like to accelerate briskly through the gears, it makes sense to utilize the peak energy to get up to speed where you can utilize the more fuel efficient top gears. And I won't deny that I love the confused looks on people's faces when my little orange economy hatch completely leaves them in the dust from stoplights. Now, that's not to say I'm doing 'Jackrabbit' starts, but rather just properly utilizing the turbo

 

[sx sonic]

Check the MPG master thread link in my sig

 

[KartRacer]

I've been running it with the tires aired up to 39 PSI, try to spend very little time in 1st gear (unless I'm showing off ) and have been using my cruise at every opportunity. I've been doing a LOT of interstate/highway driving, setting my cruise at 75 even on the interstate and at 65 on the secondary highways.

I definitely like to accelerate briskly through the gears, it makes sense to utilize the peak energy to get up to speed where you can utilize the more fuel efficient top gears. And I won't deny that I love the confused looks on people's faces when my little orange economy hatch completely leaves them in the dust from stoplights. Now, that's not to say I'm doing 'Jackrabbit' starts, but rather just properly utilizing the turbo

Sonic is this an RS, if so the 75 mph is a gas eater with the engine turning 3200 or so.

 

[Gary Grist]

I respectfully disagree

Quote ahtoxa: "This isn't always the case. I've found that accelerating briskly to get to the optimal engine speed in top gear is usually more fuel efficient. You're not flogging it, but you're not wasting time slowly climbing the revs because you're in too high a gear because you're shifting too early.Either accelerating to that optimal efficiency too fast or too slow will cause more wasted energy than necessary."[/QUOTE]

Dear ahtoxa-
With respect, I must disagree with you. The laws of phisics are immutable. The energy used to overcome inertia depends on the rate of acceleration. And the amount of energy used increases exponetially the faster you accelerate. For example, if you accelerate from 0-60 mph in 10 seconds you will use four times more energy in the form of gasoline than you will if you accelerate 0-60 in 20 seconds. If you accelerate 0-60 in 30 seconds you will only use 1/12th the energy compared to 10 second acceleration. Not only that, you will travel much further during the 30 second acceleration for 1/12th the energy than you will during the 10 second acceleration. You don't have to believe me. Just ask Issac Newton or read any high school physics book.

This is why hybrids get such good mileage. They use their battery and electric motor to accelerate, no gasoline. Once they are up to speed and the inertia is overcome, the gasoline engine cuts in and is very efficient and gets good mileage with enough energy left over to recharge the battery for the next time it is needed for acceleration.

I generally don't like hybrids. The cost and environmental savings with the better mileage is an illusion in the hybrids. With a hybrid you have maintenance on two separate drive systems, two separate fuel systems and two separate braking systems. When the battery finally needs replacement all the money you saved on gasoline you will spend on the new battery. In addition, the enviromental cost of battery manufacturing is enormous in terms of CO2 production. So in the end you don't save 'squat' with a hybrid. Maybe some day, but not with cars today. It is much better environmentally and economically to buy a good mileage car like the Sonic and drive it efficiently if you want to save money and the environment.

But, Nimda, I can certainly identify with people who like rapid acceleration and shifting; its fun. But for those who do that, don't complain about poor mileage. Gearing is most important in maximizing mileage efficiency only after you are up to speed; 6th is better at higher speeds, 5th at less higher speeds, etc.

 

[Z71]

Sonic is this an RS, if so the 75 mph is a gas eater with the engine turning 3200 or so.

You think 3200 RPM at 75 in bad? Both my Mazda Protege 1.8 liter DOHC four and Mazda 626 DOHC V6 were turning 4000 RPMs at 80 MPH in the 5th (top) gear. Mileage suffered some, but were these cars fun to drive! No downshifting at 60 MPH to pass anyone. Also, I could get down to 40 MPH in top gear and leave it there without lugging the engine in either car. Performance gearing is fun, but it will take a toll on fuel economy. And the 626 V6 had the VRIS system, which means that secondary intake butterflies in the intake manifold opened around 5k RPMs. This gave it a boost like a small turbo! It would take off from 80 to 100 MPH and accelerated strong in top gear without downshifting. Passing ability of that car at high speed without downshifting was amazing. I absolutely loved that engine and even at 340k miles it was running great. The fact that I kept it this long (bought it new) is a testimony to how good of an engine it was.

 

[Larrymer]

2nd GM I had in a row that doesn't even come close to claimed mpg. Oh well

Every automaker has to test to the same EPA cycle, which may or may not correlate well to how you actually drive the car. Some people can get 40 mpg or more, some only high 20's. All depends on conditions and how you drive.

 

[Gsrdude]

Every automaker has to test to the same EPA cycle, which may or may not correlate well to how you actually drive the car. Some people can get 40 mpg or more, some only high 20's. All depends on conditions and how you drive.

Obviously lol. Sorry meant compared other current and past vehicles.

Again, I don't care about gas mileage. Just pointing out my observations

 

[ahtoxa]

Quote ahtoxa: "This isn't always the case. I've found that accelerating briskly to get to the optimal engine speed in top gear is usually more fuel efficient. You're not flogging it, but you're not wasting time slowly climbing the revs because you're in too high a gear because you're shifting too early.Either accelerating to that optimal efficiency too fast or too slow will cause more wasted energy than necessary."

Dear ahtoxa-
With respect, I must disagree with you. The laws of phisics are immutable. The energy used to overcome inertia depends on the rate of acceleration. And the amount of energy used increases exponetially the faster you accelerate. For example, if you accelerate from 0-60 mph in 10 seconds you will use four times more energy in the form of gasoline than you will if you accelerate 0-60 in 20 seconds. If you accelerate 0-60 in 30 seconds you will only use 1/12th the energy compared to 10 second acceleration. Not only that, you will travel much further during the 30 second acceleration for 1/12th the energy than you will during the 10 second acceleration. You don't have to believe me. Just ask Issac Newton or read any high school physics book.

This is why hybrids get such good mileage. They use their battery and electric motor to accelerate, no gasoline. Once they are up to speed and the inertia is overcome, the gasoline engine cuts in and is very efficient and gets good mileage with enough energy left over to recharge the battery for the next time it is needed for acceleration.

I generally don't like hybrids. The cost and environmental savings with the better mileage is an illusion in the hybrids. With a hybrid you have maintenance on two separate drive systems, two separate fuel systems and two separate braking systems. When the battery finally needs replacement all the money you saved on gasoline you will spend on the new battery. In addition, the enviromental cost of battery manufacturing is enormous in terms of CO2 production. So in the end you don't save 'squat' with a hybrid. Maybe some day, but not with cars today. It is much better environmentally and economically to buy a good mileage car like the Sonic and drive it efficiently if you want to save money and the environment.

But, Nimda, I can certainly identify with people who like rapid acceleration and shifting; its fun. But for those who do that, don't complain about poor mileage. Gearing is most important in maximizing mileage efficiency only after you are up to speed; 6th is better at higher speeds, 5th at less higher speeds, etc.

One variable you didn't account for is that the gasoline engine's energy output is variable. Gearing also matters because it helps the engine be energy efficient. So to get the ultimate MPG you accelerate at the engine's optimal and most efficient output range and keeping it there with help of gearing.