Fuel economy (Or lack thereof)

[SVT Rob]

I have a question about fuel economy. This is my second Coyote vehicle, but it gets shitty fuel economy.

Back when I had my 2012 Premium GT w/ 3.73's and Brembo's, I would typically get a combined mpg of 19-20, and on the highway I would see numbers in the 24-25 range. This car had Roush axle-backs, custom tune, and 19x9/10 Boss 302 LS wheels on it.

With my current 2013, I'm seeing a max of 20.5 on the highway, and a combined of 15.5-16.5. This is a 2013 Premium GT w/ Track Package and Recaro's. I pulled the DTC's, nothing was found, the car has a stock tune on it. I've recently added an MBRP cat-back, but the fuel economy didn't change up or down with that.

As soon as I get the wifes SHO back from the dealership for maintenance, I'll be dropping this off. Just curious if someone has/had experienced this, and could possibly point me in a direction to look ati.

 

[paulyboy928]

could be the stock tune.

 

[87hatchy]

Do you have different wheels on the 2013 than you did on the 2012? When going from the base GT wheels to 19x9.5 SVE drifts on all four corners, which are much bigger and heavier, my MPG went down about 2mpg both on highway trips and around town just from the heavier wheels and tires.

Also, while you may be thinking you are comparing the exact same things since its the same engine and whatnot, that isn't necessarily the case. Ford is constantly tweaking and fine tuning calibrations between model years. So, A) the 2013 stock tune is probably slightly different than the 2012 stock tune (Remember they changed horsepower in 2013: Went from 412hp in 2011-2012 to 420hp in 2013), and B) The formula for calculating MPG is probably refined in the 2013 car and more accurate (just a guess, but I would assume its been tweaked)

 

[SVT Rob]

Stock track package wheels on the 2013, Boss 302 LS wheels (19x9 and 19x10) on the 2012

As for calculating mileage, I've always filled the tank, wrote down my mileage, gallons, price per gallon, and total price. I track it via fuelly.com so I'm not using the onboard diagnostic tools in the vehicle. There is a DEFINITE discrepancy between the two vehicles. My 2012 only lost ~1mpg going from stock tune to custom tune.

 

[noldevin]

Does the newer car have stickier tires?
How many miles are on it? Maybe it needs a maintenance item that is reducing efficiency (filters, plugs, etc).

 

[SVT Rob]

Does the newer car have stickier tires?
How many miles are on it? Maybe it needs a maintenance item that is reducing efficiency (filters, plugs, etc).

2012 - Pirelli P-Zero 255/40 in front, 285/35 in rear. It had 43k miles on it when I sold it. I didn't do any other maintenance aside from oil changes at the dealership. Ford also rebuilt the rear end a couple months before I sold it, it was howling on accel/decel, they replaced ring, pinion, carrier, all bearings, all seals, and both axles under warranty.

2013 - Goodyear Eagle F1 Supercar, 255/40 all around. Currently has 49k miles on it. It had a new paper filter in it, I just put in a new AEM drop-in filter. I bought new plugs, but haven't put them in yet. They came in late last week.

 

[noldevin]

2012 - Pirelli P-Zero 255/40 in front, 285/35 in rear. It had 43k miles on it when I sold it. I didn't do any other maintenance aside from oil changes at the dealership. Ford also rebuilt the rear end a couple months before I sold it, it was howling on accel/decel, they replaced ring, pinion, carrier, all bearings, all seals, and both axles under warranty.

2013 - Goodyear Eagle F1 Supercar, 255/40 all around. Currently has 49k miles on it. It had a new paper filter in it, I just put in a new AEM drop-in filter. I bought new plugs, but haven't put them in yet. They came in late last week.

Is it possible the previous owner did have a tune on it and demodded without removing the tune?

 

[SVT Rob]

I checked it out with my X4, it doesn't appear to have a tune on it. It could very well be possible, but I'm inclined to say no. The X4 is willing to put an aftermarket tune on it, but I haven't done so yet.

I mean, honestly, the only concern I have is the fuel consumption of the car, going 200 miles on a tank of fuel kinda blows. Overall, it seems to run/drive really well. Ran a 12.81 @ 110 mph closing weekend at MoKan a couple weeks ago.

 

[noldevin]

That's pretty solid. Maybe its your driving habits? lol
maybe have the alignment checked, a bad alignment could cause a lot of tire resistance.

 

[SVT Rob]

That's pretty solid. Maybe its your driving habits? lol
maybe have the alignment checked, a bad alignment could cause a lot of tire resistance.

I'll have them check the alignment when I drop it off.

As for driving habits, I drive about the same regardless of the vehicle I'm in. On the highway, I set the cruise control at 65 mph, and made a 127 mile drive back from the track, all highway. I was able to get 21 mpg out of that trip. In my 2012, I was able to set the cruise control at 70 mph, and made the same highway trip and got 25 mpg. It also ran a 12.59 @ 113 mph (after tune).

Ford doesn't seem to think there's a drastic difference in fuel economy, they list at 16/25 and 19 combined for both the '12 and the '13. I'm seeing about a 3-5 mpg difference in mine.

/shrug Gotta drop the SHO off first, it's got more pressing issues to deal with (trans has started slipping, heated steering wheel doesn't work, it's got a vibration between 65-80 mph, and there's a recall for the fuel pump module). Once I get that one back, I can drop off the GT.

 

[noldevin]

I would also check for oil in the intake manifold. These cars do get some blowby and that could definitely hurt your fuel economy. Would be a simple fix with a catch can

 

[SVT Rob]

Did the plugs in it tonight after work, they all looked ok. #8 was damp on the threads and it smelled funny, but overall it still looked ok. Went and picked up my oldest at the high school, never got above 40 mph, the idiot gauge in the center reported 19.8 mpg by the time I got home, total drive of ~11 miles. That's considerably better than the 16.3 mpg that it was reporting as my combined for this tank of fuel, which is a good 65% highway driving.

 

[Silbult14]

Your mileage does seem a little low to me. I have a base '14 GT, manual trans car with a track key and I get anywhere from low 22's to high 23's combined. Our driving habits and conditions may differ as well. I live in a rural area so my driving is biased towards highway use. I never hammer on it or any other car until it's completely warmed up. Once it is however, I do get on it from time to time. This includes pushing it a bit on twisty back roads with a fair amount of heel and toe downshifting and powering out on corner exit as well as simply running it through the gears on straight open stretches. Other times I drive like the old guy I am [ I am 72 ]. As for the car itself, it has 24,000 some miles on it which is a lot since it's not my daily driver, but when you live in the country every place you go involves a fair # of miles. It's just hard for me to keep my hands off it. A friend of mine has one too and he calls it "gearhead crack". It has the standard 3:31 gears and either 18x8 wheels with 235x50x18 tires [ cold weather ] or 19x9 Boss 302 wheels with 255x40x19 summer tires. Either way they are right at 27 inches in diameter with the all seasons being just a touch larger. It also has a Bob's oil catch can. I change oil [ Mobil1 5w30 ] every 4,500 miles and it dosen't use any measurable oil in that time, although a small amount does accumulate in the catch can. Since I have a track key I usually run 91 or higher octane fuel even though I usually use the standard key. If I am going on a long highway trip or if I know I won't be using the track key for awhile I'll just use 87 with the standard key and it runs fine. I generally run between 75-80 mph on the interstate. My "gearhead crack" buddy has seen 26+ with his 3:55 geared car on the interstate. For whatever reason I've never seen over high 23's so far.

 

[KushBandit]

I can get a max of 29mpg on the highway and 18mph in the city when I drive like a granny. Something is definitely funky on your end.

 

[Brutal Metal]

the auto trans are supposed to be 19 city right? I get 17 being granny.

 

[noldevin]

19 city in a mustang? fat chance

 

[SVT Rob]

So, I've had a chance to put some mileage on it (about 80 since the plug change), and the fuel economy shows to be a bit better. It will take a few tanks of fuel for me to be sure, but right now it's sitting at 18.9 mpg combined highway/city. Before the plugs, I was running 16.3-16.5 combined.

This is a lot closer to what I was getting out of my 2012, so if it stays around here, I'll be happy. I didn't drive my 2012 in the winter, so I'm counting on a bit of loss with the car idling to warm up in below-freezing temperatures.

Thanks for all the input, I'll keep updating as I go.

 

[Malern28us]

I have a question about fuel economy. This is my second Coyote vehicle, but it gets shitty fuel economy.

Back when I had my 2012 Premium GT w/ 3.73's and Brembo's, I would typically get a combined mpg of 19-20, and on the highway I would see numbers in the 24-25 range. This car had Roush axle-backs, custom tune, and 19x9/10 Boss 302 LS wheels on it.

With my current 2013, I'm seeing a max of 20.5 on the highway, and a combined of 15.5-16.5. This is a 2013 Premium GT w/ Track Package and Recaro's. I pulled the DTC's, nothing was found, the car has a stock tune on it. I've recently added an MBRP cat-back, but the fuel economy didn't change up or down with that.

As soon as I get the wifes SHO back from the dealership for maintenance, I'll be dropping this off. Just curious if someone has/had experienced this, and could possibly point me in a direction to look ati.

I have a 2011 GT very and I have noticed that I get significantly better gas mileage with 87 octane vs 93 octane. I currently get 25mpg with the top up/23 mpg with the top down on 87. With 93 octane it is closer to 21mpg top up and 19 mpg top down. No tune and 275/40/19 on all four corners.

 

[SVT Rob]

I have a 2011 GT very and I have noticed that I get significantly better gas mileage with 87 octane vs 93 octane. I currently get 25mpg with the top up/23 mpg with the top down on 87. With 93 octane it is closer to 21mpg top up and 19 mpg top down. No tune and 275/40/19 on all four corners.

I plan on running a custom tune for 93 octane, so I'm just in the habit of running 93 all the time. I've currently got two 91-octane tunes and a 93-octane tune, but running the stock tune on the car.

I had to run 93-octane in the SHO as well. Always force of habit, for me LOL.

 

[KushBandit]

the auto trans are supposed to be 19 city right? I get 17 being granny.

The autos are rated for 18mpg/city from the factory.

19 city in a mustang? fat chance

I get 18mpg in the city with my auto. I rarely get it cause I rarely baby the car, however it's possible.

Edit: factory mpg adjustment