Should I Be Happy With My Mpg?

[03_TrueBlue_GT]

Hey guys lately when I drive my Mustang on the way back to college I noticed that I average about 20mpg on my trips to and from school. I do drive around 65-80mph but due to the traffic I am never able to keep a steady speed. I am wondering if y'all think it is possible for me to get at least 22-23mpg with the way my car is currently set up? I do realize my aftermarket 3.73 gears and heavier rims with the wider tires hurt my gas mileage goals but I should still be able to get at least 22mpg or above?
I did try going 70mph one time but I was only able to get 20.5-21 mpg those times I did try it. So with 3.73 gears and a manual transmission do these cars like to go 60-65mph only to get good mpg? I remember the sweet spot for my F150 was about 60mph to get good gas mileage. Sorry to post this thread but its something that I was wondering about lately, I would like to get at least 300 miles on a tank of gas but lately on highway drives I am only able to go 260-280 miles before the low fuel light comes on. I do realize that its more than likely my driving that is keeping me from reaching my goals to get better mpg, but it can a little difficult to go a constant 65-70mph on the highways out here where everyone with newer cars can go faster and not worry as much about suffering a gas mileage penalty.

Some information on the car
- Spark plugs have about 25000-30,000 miles on them
- Fuel injectors were cleaned recently at my local dealership
- I run Mobil 1 full synthetic 5w-20 oil
- tires are at 33psi each
- As of now it has 121,500 miles on it

 

[IIGood]

I guess with your gears and tires, what you're getting is about right. Maybe bump the pressures up a little more and you might get a touch extra.

My stock '03 GT (I run 35 psi in the tires) gets ~20 mpg around town consistently. The best I've gotten out of it was 27 mpg on the highway, running at around 70-75 mph.

I do reset the trip meter at every fillup and watch it like a hawk. LOL. That way I can tell if something's going on, should the mileage go down on a tank. It's never been anything more than pumping up the tires when I have had decreases in mileage.

 

[Mustang5L5]

I would say gears and tires do hurt

I used to get 26-27MPG with 87 octane consistently with my stock '03 GT. I loved my 3.27's for that reason and never wanted to change them

 

[03_TrueBlue_GT]

I guess with your gears and tires, what you're getting is about right. Maybe bump the pressures up a little more and you might get a touch extra.

My stock '03 GT (I run 35 psi in the tires) gets ~20 mpg around town consistently. The best I've gotten out of it was 27 mpg on the highway, running at around 70-75 mph.

I do reset the trip meter at every fillup and watch it like a hawk. LOL. That way I can tell if something's going on, should the mileage go down on a tank. It's never been anything more than pumping up the tires when I have had decreases in mileage.

Yeah I will add some more psi to the tires and try to drive around 65mph more on the freeway. I remember when I bought the car it had no problem going 325miles before the low fuel light came on.

I would say gears and tires do hurt

I used to get 26-27MPG with 87 octane consistently with my stock '03 GT. I loved my 3.27's for that reason and never wanted to change them

Yeah I figured they hurt it a lot. I have been debating on whether I should go back to my stock 3.27's and get rid of the staggered rim setup to improve the gas mileage because I want to supercharge my car with a Vortec or Pro charger down the road anyways.

 

[COramprat]

I average 22 in my car now on the highway at 70 with mods below. All depends on how you drive.

 

[SRT Handz]

I can get 21+ MPG with my supercharged and tuned GT. Even while beating on it and driving around hard, i still averaged 18MPG on fuelly.

 

[Kilgore Trout]

Suggest not admitting you paid a stealership to "clean your injectors"...

I get about 8 mpg but I drive my car properly, like I stole it.

The correct psi is 32.5 do not add more.

 

[03_TrueBlue_GT]

Suggest not admitting you paid a stealership to "clean your injectors"...

I get about 8 mpg but I drive my car properly, like I stole it.

The correct psi is 32.5 do not add more.

I trust McRee Ford, we buy all our new Fords from them and they have treated us great the whole time. It did help the car because afterwards it had better throttle response and help cured my spark knocking. I would drive my car like I stole t if I could but its my DD and I dont want to break something. :/

I know my car wasnt made for getting great mpg but I was just wondering how I can improve it instead of buying a boring 4 door commuter.

 

[Kilgore Trout]

summer gas gets better miles

 

[03_TrueBlue_GT]

summer gas gets better miles

Not sure if you are serious or not...
Meaning I dont know if I should believe it lol, I haven't heard that before. Unless the additives for keeping fuel from freezing cause bad gas mileage.

 

[restomod66]

Summer gas and Winter gas are different blends that will yield slightly different results, use the Google to find out more details. Your rear gear will hurt fuel mileage a little bit on the freeway, but I think you should still be seeing better than 20-21 MPG on the freeway regardless. I don't know what type of spark plugs you're running at the moment but I would consider throwing in a fresh set, cleaning your MAF sensor/air filter, and upping your tire pressure a bit. I recently switched to NGK Iridium plugs and thus far I've been very happy with the results. The car always fires up quicker than before and my idle seems to have smoothed out a little bit as well. The plugs are rated to last 100k miles so it's likely the last set I'll ever purchase for the car. BTW I can easily knock down ~27 MPG on freeway road trips in my GT, my city MPG however is always around 13-14 b/c I have an issue with my "driving style".

 

[Gearbanger 101]

Adding attentional air pressure to your tires will help. There's no right pressure (not exactly sure where Trout is pulling his 32.5psi figures from?) for your tires. The amount of air pressure will depend on the manufacture and type of tire. Generally, adding another 5lbs or so of pressure to your tires won't have any ill effects. Add too much though and you'll start to bow the tire in the middle and wear it down the centre.

That will help a little, but you're biggest improvement is going to be reducing y our speed. You are correct in assuming slower speeds will yield better results. Running 80mph down the express-way is what's draining your tank and you'll never get the mileage you want driving like that. Pull the car over to the slow lane and be patient. Pull away from stop signs and traffic lights like you've got a hard boiled egg between your foot and the accelerator and you're trying not to crack it. Keep passing to a minimum and shift up into high gear at as low an RPM as your engine will allow.

The sad fact of the matter, is that in order to try to get gas mileage like a Prius, you've also got to drive your car like one too.

 

[03_TrueBlue_GT]

Thanks for all the responses and advice guys I appreciate it. I know I need to keep it around 65-70mph to get good results, but its so hard to do lol.

 

[Gearbanger 101]

Thanks for all the responses and advice guys I appreciate it. I know I need to keep it around 65-70mph to get good results, but its so hard to do lol.

Cruise control is your salvation, bro.

 

[03_TrueBlue_GT]

Cruise control is your salvation, bro.

Yeah I need to reconnect the cruise control plug back into the port, when I swapped out my clutch and firewall adjuster I had to take it off to work on it. I forgot where it was supposed to plug in and just haven't gotten around to figuring out where it plugs back into. If anyone knows I would really appreciate the help.

 

[Flghtmstr1]

Speed is everything with these cars, as they're not very aerodynamic. I once had a long drive ahead, a CD player full of discs, and no reason to hurry, so as an experiment, I sat back, relaxed, and set the cruise control to 55. Even with 3.73s and a blower, I averaged 30.1 mpg on that trip. If you have the patience, you can do the same. If you try the same experiment and find that you're still getting poor fuel economy, post back here and we can help you start diagnosing the issue.

 

[Tx3nC]

On a different vehicle, I improved the MPG I was getting by short shifting it at 2000 RPM and keeping at 1900-2000 RPM on the highway. It was a 3.0V6 with a 5 speed manual trans. IIRC I was able to go from the low 20 mpg to about 26, which for this vehicle combination was pretty respectable.

The formula for better MPG is pretty set. Lower mass, lower rolling resistance, less power. The internal combustion engine is pretty fixed at a mid 20% thermodynamic efficiency. It is also fixed at approximately 14:1 air to fuel consumption ratio. Many times to increase power, we try to increase airflow into and out of the engine (intake, air cleaner, exhaust modifications). When we get more air into the engine, it needs more fuel to keep from running lean and burning up or breaking something. Anything you can do to make any of the factors affecting mileage better will give you an increase. Less mass -- empty crap out of the car you don't need. Less rolling resistance -- narrower tires, harder compound of rubber in the tire, increase in air pressure all can help. Then engine will consume however much air it does per revolution and will burn fuel to match. Keeping the RPMs down is the easy way to use less fuel. The higher gear you can use, the farther you will travel per revolution, better for mileage.

Really, the easiest way to better fuel economy is less mass with less power. That's why manufacturers are offering cars like the Fiesta. Small, light, low power. Less mass also has the side benefit of making less power seem like more. An 85hp motorcycle is more fun to ride and faster than an 85hp pickup truck.

Now manufacturers are playing around with trying to vary the amount of air an engine uses per rev. GM is using selective cylinder deactivation. Ford is going with their Ecoboost. A turbo charger can have the effect of increasing power by processing more air through the engine than natural aspiration, but you need more fuel to do it. If the turbo can be cut out when not needed and let the small engine run NA when less power is needed, you can have an increase in fuel mileage but have more power available when needed by bringing the turbo online.

Just some random thoughts.

 

[03_TrueBlue_GT]

Thanks for the replies everyone. I managed to get 22mpg on my way back to college. I just stayed at 65-70mph and tried to not change lanes as much as I could. Also I cannot figure out for the life of me how to get my cruise control to work again. When I did my clutch swap and clutch quadrant adjuster I thought I connected it back up to the right ports but it wont work now... I will try to post a picture of the current setup on my clutch quadrant adjuster and maybe someone will see if its in the right port or not.