MPG + Maintenance Questions

[Two-Tone]

Sup y'all.

Had my 2015 Performance Package Premium with Ford Performance tune and MBRP Race catback system for 2 weeks now. Seems to run like a top, although I wouldn't say I'm familiar enough with it to tell much of a difference between whether it's running well or not. MUCH faster than what I'm used to, and truly a pleasure to drive.

Wanted to run my setup and driving conditions by you all to see if my MPG figures seem normal.

Getting 24 MPG and change on this most recent tank, about 26 when I drove it back from buying it for about 5 hours on the highway (with a low tire, I later found out) and 21 on my first tank, albeit with a decent amount of hotrodding around, idling with the remote start and when starting up to let the engine "rev down" on cold starts (does anyone else do this? Is it necessary?

The FP tune has been installed for close to 1000 miles now, not sure if it still needs to learn my driving habits at this point? I've only done a handful of hard pulls on my first tank, and wouldn't say I've even floored it yet. 32,000 miles on the odometer.

Anyway. Here goes:

• 75% hwy driving on my commute, about 17 miles on the freeway twice a day, another other 15% in stop and go traffic and 10% steady city driving
  
  
• Ambient temps between 85 and 115-degrees (85% of commute in 100+ temps)
  
  
• 91 octane Costco gas (highest where I live)
  
  
• Automatic transmission
  
  
• 10-gallon Techron treatment in this current tank
  
  
• Switched to Nitto NT555 G2 265/40R19 tires all around about halfway through this tank (plus-zero size with wider section width over stock, which I know creates more rolling resistance)
  
  
• Only use A/C and cooled seats after the vehicle is running, (not left on under cold or remote start)
  
  
• Have stayed out of sport mode on this tank, and have generally stayed at around 50% throttle when getting on the freeway while trying to stay out of boost.
  
  
• 50% oil life
  
  
• Not sure on spark plug condition -- all prior maintenance had been done on time at a Ford dealership every 7,500 miles.
  
  
• Tire pressure good, showing close to 40 PSI at speed
  
  
• General freeway speed between 70 - 80 MPH, with passing pulls up to 90 maybe once a week. (Also trying to avoid ecoboom, still need to check which low pressure fuel pump sensor I have)
  

I realize with the taller gear ratio I won't get the full 32 highway on the sticker, but I wonder how much this extreme heat has to do with this MPG I'm getting that I'm frankly not all too happy with.

Also, on my first tank my trip computer had me getting around 23 MPG, but when I calculated it manually it came out to 21 and change. Are the trip computers in these as inaccurate as some other cars?

Any thoughts, insights, suggestions greatly appreciated. Big reason I bought this car was for its decent gas mileage, and while I realize what I'm driving, want to better understand what I should expect.

As it is, I absolutely love this car and plan on owning it for quite some time -- and to be getting close to 400 HP and get 24 miles per gallon I still consider a feat in and of itself.

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[offcamber]

I’m never on the freeway and I average 23mpg. Sounds like you probably are close to max mpg with your driving style. Cooler ambient temps will benefit the overall performance so wait for Fall. A larger inter cooler is the last piece you should consider to maximize performance.
To improve fuel efficiency further you need to reduce weight. Take out the spare tire if you have one. Mount lightweight wheels/tires. Staying below boost helps extend a tank of gas.....but what fun is that?

 

[TorqueMan]

Sup y'all.

Howdy, welcome to the forum. Congrats on the new Pony.

Getting 24 MPG and change on this most recent tank, about 26 when I drove it back from buying it for about 5 hours on the highway (with a low tire, I later found out) and 21 on my first tank, albeit with a decent amount of hotrodding around, idling with the remote start and when starting up to let the engine "rev down" on cold starts (does anyone else do this? Is it necessary?

This doesn't sound out of line considering the highway speeds you report. Your car has wider tires and lower gearing than the cars used to get the EPA mileage figure (which is 31 highway, not 32). Idling won't burn a lot of gas except when it's cold. I don't think a rev down is at all necessary. Drive it carefully and keep it out of boost for the first five minutes or so after a cold start and you'll be fine. Plus you won't be wasting gas sitting still.

The FP tune has been installed for close to 1000 miles now, not sure if it still needs to learn my driving habits at this point? I've only done a handful of hard pulls on my first tank, and wouldn't say I've even floored it yet. 32,000 miles on the odometer.

It's dialed in at this point.

Switched to Nitto NT555 G2 265/40R19 tires all around about halfway through this tank (plus-zero size with wider section width over stock, which I know creates more rolling resistance)

And wind resistance. At the typical speeds you're driving aerodynamics is the biggest factor for fuel economy. Anything you add to the parts of the car that hit the wind, like wider tires, will make the car less aerodynamic and decrease economy.

General freeway speed between 70 - 80 MPH, with passing pulls up to 90 maybe once a week. (Also trying to avoid ecoboom, still need to check which low pressure fuel pump sensor I have)

This is the primary reason you are seeing lower economy, especially when combined with the lower gearing and wider tires. EPA estimates assume an average of 55 mph. Depending on the aerodynamics, 70 mph can reduce EPA figures by as much as 23%, and 80 mph can reduce it by as much as 28%. Guess what? If you reduce the EPA estimated economy of 31 mpg by 23% you get 24 mpg.

I realize with the taller gear ratio I won't get the full 32 highway on the sticker, but I wonder how much this extreme heat has to do with this MPG I'm getting that I'm frankly not all too happy with.

I don't think you're doing enough stop-n-go for the heat to be a factor. If the engine--especially the intercooler--gets heat soaked the ECU will compensate with a richer mixture to protect the engine. This would really only be a factor if you were doing a lot of stop-n-go with a heavy foot; it doesn't sound like that's the case.

Also, on my first tank my trip computer had me getting around 23 MPG, but when I calculated it manually it came out to 21 and change. Are the trip computers in these as inaccurate as some other cars?

My computer typically reports 1-2 mpg higher than measured.

As it is, I absolutely love this car and plan on owning it for quite some time -- and to be getting close to 400 HP and get 24 miles per gallon I still consider a feat in and of itself.

There you have it. You're getting remarkable performance AND economy. Enjoy it!

 

[dausmus]

I have a 10spd with 3.55 gears. On hwy 75ish I can get 32mpg all day.

 

[TorqueMan]

I have a 10spd with 3.55 gears. On hwy 75ish I can get 32mpg all day.

The auto-trans 2018s are rated at 32 mpg highway, partly based on changes to engine tuning, but also because of improved aerodynamics. At higher speeds aerodynamics outweighs all other factors when it comes to fuel economy. Still, I'd say your car is performing better than average when it comes to economy. Congrats!

 

[Maggneto]

Tire pressure on EB/PP is 32 cold and about 35 hot with air filled tires so it would appear you are running about 36 cold? Watch out for pot holes running that much oewsspre in the tires.

In mixed driving my wife gets 25 commuting to work. City driving nets about 21.

 

[TicTocTach]

I've put 8 tanks of 93 through my EBPP A10 so far, and the average mileage is 22.78 mpg over 2100 miles. The on-board trip computer overestimates mileage between 10 and 20%, so don't rely on whatever math it uses. My best tank to date was nearly all highway @ ~80 mph, 24.99 mpg - indicated 30.1 mpg on the trip computer. The only "modification" from fully stock is higher tire pressure. I run 38 psi cold, and have not yet checked to see how sensitive the car is to tire pressure.

I'm concerned with mileage as this is my DD and I'm replacing a Honda Fit that averaged 33.41 mpg over 108,000 miles. I'm content giving up some mpg for the extra 200hp, but I'm still a bit disappointed in the EB mileage. I try not to think about that when I'm merging onto the highway or passing something without having to plan it for a few miles. That said, I use some of the hypermiling techniques that I learned with the Fit, so hopefully I'll figure out what it likes and settle in somewhere north of 25 mpg average before too long.

Clair

 

[TorqueMan]

My best tank to date was nearly all highway @ ~80 mph, 24.99 mpg - indicated 30.1 mpg on the trip computer.

Unless you get a hellacious tail wind you will never see north of 25 mpg at 80 mpg; this car is simply not aerodynamically clean enough. Try this test (if you can stand it): drive sanely for a tankful of gas while keeping highway speeds under 70, then report what you get. I routinely see 29-30 mpg (measured, not computer-reported) with my 2017 non-pp. I'm guessing even with the shorter gearing you'll still get 27-28 mpg.

 

[PRG3k]

The early stick shift, performance pack, premiums were about the worst ones for MPG. I have one. Close gear ratio, manual transmission, and full weight of the stereo equipment, leather and other accessories of the premium pkg gives me around 22/23 mpg. An entire tank spent on the highway would net me 27mpg. But with this gear ratio, there's no highway speed that's going to get you there fast and save gas.

I still love banging through the gears and flat foot shifting this thing.

 

[TicTocTach]

Unless you get a hellacious tail wind you will never see north of 25 mpg at 80 mpg; this car is simply not aerodynamically clean enough. Try this test (if you can stand it): drive sanely for a tankful of gas while keeping highway speeds under 70, then report what you get. I routinely see 29-30 mpg (measured, not computer-reported) with my 2017 non-pp. I'm guessing even with the shorter gearing you'll still get 27-28 mpg.

It's strange that there are no real numbers out there for the S550 drag coefficient. I guess if it's nothing to be proud of, Ford may be pretty tight-lipped about it. To me it SEEMS like it ought to be pretty slick - classic fastback roofline, wheels are close to the fender openings, decent airdam, minimal grille opening, nice flush glass... it's got lots of the right parts to get there. Ecomodder has some aero info for the 1994-2004 Mustang Cobra, but that's it - I'll assume that the S550 is in that ballpark for now:

https://ecomodder.com/wiki/Vehicle_Coefficient_of_Drag_List

Make - Model - Year - Cd - Height - Width - Area - CdA
Ford - Mustang - '94-'04 - 0.37 - 52.5 - 73.1 - 21.6 - 7.99

They have a neat road HP calculator as well:
https://ecomodder.com/forum/tool-aero-rolling-resistance.php

Mustang assumptions above show ~40hp at 80mph, and not quite 19mpg. Ouch.

My mileage benchmark is my previous DD - a 2008 Honda Fit. Pretty small frontal area, but I wonder if it isn't about the same as the Mustang since it was a pretty tall car. Kind of a brick otherwise, but there has been a lot of work making hatchback bricks more aerodynamic over the years and it shows. The 1.5L engine was turning ~3,400 rpm @ 75 mph, and mileage would drop significantly if I drove much faster - VTEC began to activate around 3,500, so 75 mph was my goal most of the time. Mileage was naturally better at 60 mph as well.

Make - Model - Year - Cd - Height - Width - Area - CdA
Honda - Fit - '06-'08 - 0.35 - 60.0 - 65.9 - 23.1 - 8.085

Fit assumptions above show ~36hp at 80mph, not quite 21mpg. That's probably a little conservative compared to what I actually saw, but it's an easy 10% better than the Mustang in this comparison.

Mustang is turning 2,160 @ 75 mph, so only 63.5% of the Fit engine speed - almost exactly the same volume of air & fuel should be moving through the engine all else being equal. Throttle on the Mustang needs to more open to make more hp at the same rpm, so there's the mileage difference.

I've got a 4-hour (each way) road trip coming up, and will have the opportunity to check nearly-steady 80mph on the way down, and nearly 70mph on the way back. I'll do a fill-up on both ends of that trip and see what comes back.

 

[TorqueMan]

It's strange that there are no real numbers out there for the S550 drag coefficient. I guess if it's nothing to be proud of, Ford may be pretty tight-lipped about it. To me it SEEMS like it ought to be pretty slick - classic fastback roofline, wheels are close to the fender openings, decent airdam, minimal grille opening, nice flush glass... it's got lots of the right parts to get there.

But it's wide. And many people who install aftermarket intercoolers leave the grill shutters inactivated, so the large grill becomes a parachute.

I've got a 4-hour (each way) road trip coming up, and will have the opportunity to check nearly-steady 80mph on the way down, and nearly 70mph on the way back. I'll do a fill-up on both ends of that trip and see what comes back.

That sounds like an excellent plan to collect some data. I would include the following in your calcs:

• Elevation at your start/end points
• Reported wind data along the route
• Significant difference in load (total weight of the car)

 

[xmadror]

I was kinda surprised at my "bad" mpg. I had a subaru brz before my ebm, my averave with it was ~24.
Now with the ebm I'm at ~17mpg. I dont drive in a manner to save gaz but I drive the ebm as hard as I used to drive the brz.
7mpg is more then I expected. Can't say that I care too much though.
I do however have a 3.73 diff, ford performance tune, and 295 mpss, while the brz while 4.1 diff, 215 width tire with less grip.

 

[TicTocTach]

That sounds like an excellent plan to collect some data. I would include the following in your calcs:

• Elevation at your start/end points
• Reported wind data along the route
• Significant difference in load (total weight of the car)

First leg of the trip complete. Tank included 24 miles of my normal commute (90/10 highway/city) and 13 miles of stop-n-go traffic getting out of town today. Traffic through Austin was 35-65mph, but the remainder of the trip was at 80mph on cruise control. Headwinds varied from 10-20mph nearly directly out of the south, so head-on. Ambient temps started at 101, dropped to 90 at the end. Load in the car is me, a full tank of gas, a bag of chips... well, a small duffel bag and a backpack. And my fly rod.

Elevation difference start/end is only about 575 feet:

20180825_80mph-profile by clair_davis, on Flickr

Fill-up saw 14.117 gallons over 337 miles, for 23.87mpg actual, 25.5mpg per the trip computer. Would likely have been at or above 25mpg if not for nearly 30 minutes of stop-n-go a the start of the trip. That would have been on par with my last 80mph trip.

Return trip will be a little longer, with more elevation changes mid-way, and I'll make that drive on Friday.

 

[Two-Tone]

First leg of the trip complete. Tank included 24 miles of my normal commute (90/10 highway/city) and 13 miles of stop-n-go traffic getting out of town today. Traffic through Austin was 35-65mph, but the remainder of the trip was at 80mph on cruise control. Headwinds varied from 10-20mph nearly directly out of the south, so head-on. Ambient temps started at 101, dropped to 90 at the end. Load in the car is me, a full tank of gas, a bag of chips... well, a small duffel bag and a backpack. And my fly rod.

Elevation difference start/end is only about 575 feet:

20180825_80mph-profile by clair_davis, on Flickr

Fill-up saw 14.117 gallons over 337 miles, for 23.87mpg actual, 25.5mpg per the trip computer. Would likely have been at or above 25mpg if not for nearly 30 minutes of stop-n-go a the start of the trip. That would have been on par with my last 80mph trip.

Return trip will be a little longer, with more elevation changes mid-way, and I'll make that drive on Friday.

Wow. Very comprehensive -- color me impressed.

 

[BlueBoost]

Very interesting stuff. I find it hard to bring my average mpg's over 24 while driving economically. For you manual guys out here, how do you drive to get decent mpg's? Do you completely stay out of boost and take the car to 3k rpm to keep up with traffic? Or do you go into a little boost and shift earlier? I am just trying to find the sweet spot for efficiency.

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