i try to stay around 2-2500 rpms when shifting, but its hard to be disciplined all the time

 

and even harder if you drive a 2.3:eeek:

Other things to help save fuel. Stay on the freeway if possible-backroads tend to drop MPG. Smoother dry roads are better MPG than rough or wet streets. On hills-coast down when possible (neutral)...the several hills I frequent, one is 5.2 miles downhill and straight. Kill engine at top and coast. Usually at 70-72 mph at the bottom, then let it coast back to about 60, key back on, bumpstart in 5th and keep going. Drafting does work but you don't necessarily need to be RIGHT behind a truck. Just behind them at a safe distance works...and works REALLY good if you're behind a low profile van-style trailer (like a Mayflower moving truck or a race car rig) and in front of another truck. If they can sandwich you in, you'll knock out better MPG. Keep the tires inflated to at or near the max psi that is stamped into the tire. You have to read to find it. It'll say something like max load XXXX lbs or kg at XX psi. Mine are max 44 psi and I run them at 40-42 cold. If you can manage it, a block heater helps get the engine temp up quicker. Cold engines use more fuel (enrichment). Plus you have heat quicker in the winter. I used block heater in summer too. Electric fan is worth some MPG if you don't already have one. Using the lowest possible RPM to do the job helps-but its' harder with a 5 speed due to concerns with bogging the motor (especially with a 4 cylinder). Good front alignment helps. Bent rear axles HURT MPG. Tire balance is worth 1-1.5 mpg. And not a cheapie balance-a GOOD balance. Lighter tires are worth some MPG-same for lighter wheels but we're splitting hairs there. Make sure the rotors aren't dragging. Same for the drums-if you have drums on the rear. Front air dam works even removing the factory one dropped my MPG down a little...about 1 mpg but what I am doing, every little bit adds up. Keep good, clean, fresh spark plugs in the engine, a good air filter. On my 2.3 the factory air box with the heat tube gets better mpg than a cold air kit style open filter. Leave the EGR hooked up-it's worth a couple MPG. Eliminating the power steering is worth a MPG or two. A/C on costs 2-3 mpg on my 2.3. Probably less with a V8. Make sure the thermostat is as close to stock temp as possible. 7.3 diesels are notorious for this-if they aren't up to operating temp the mileage SUCKS. Ours picked up 7 mpg (from 13 to 20). If the front end pulls to one side or the other, you have to hold the wheel in the opposite direction to correct-and that loads the pump more and costs mpg. So a good alignment helps in more ways than one.

 

IDK if id run the pressure up to the 40s as the center tread may wear quicker. But I do try and keep them at 36psi. I think stock 99-04s call for 32 or 34psi.

Ive always wondered about air dams. Mostly the Mach 1 lips for the 99-04. Im guessing the fuel they save would take years to pay for a $120 chin. IF it did help. I have thought of doing a little experimenting with underbelly pans. But I havent found a cheap durable material that would make it a cost effective investment.

 

Air dams can certainly improve fuel mileage. The problem is, they have to be low to the ground. I doubt the Mach 1 lip is effective, as it is still quite high from the ground.

 

The tires I have always used wear BETTER with max psi in them. I usually get 60,000-70,000 miles on a set of 295/45-18s on my Lightning when about everyone else is getting 35,000-45,000 max on the same tire (hankook Ventus). My mustang has a set of CHEAP (less than $100 for all 4) junk tires on it. Sidewalls say 44 psi. I run them around 40-42 normally. So far they've got 41,600 miles on them and they still look new as far as tread depth. I did run them down to 34 psi once and trust me-it was an odd feeling. Rear end was wiggly. Front end mushy. Ride quality was "ok" but too soft for my preference. The "old" tires that were on it were a different brand and at 40 psi it drove like a go-kart. These cheapies have a mushy sidewall. Better ride but way worse handling!

Have also checked tire temps across the tread at 42 psi in the Mustang and it was within 2-3 degrees all the way across-an indication that the tire was not scrubbing any worse in any particular part of the tread.

Why the manufacturer puts 30-some odd PSI on the door tag is beyond me. Underinflating them causes more wear and driveability problems than running them close to max.

Had to edit: Have noticed in the last few times I've checked MPG that it was down to 27-28 which is typical for most 2.3 Mustangs. The other day at work I decided to check tire pressures. They were 25-27 (all were different but not that far off of each other). I suspect due to cold weather we've been having. Highs in the 20's lows close to zero. Pumped them up to 40, MPG back up to mid to upper 30's without a single other change in either driving habits, or otherwise. Wait..temps are up. Was in the upper 40's for a couple days until a few days ago when we got a heat wave, but I havent' checked MPG with the warmer (60's) air.

 

Todd, id have to disagree with you on the no A/C. Or at least say that my testing isnt consistent with your line of thought. I found that the A/C didnt play all that much of a factor. Mythbusters I believe came to the conclusion with their test vehicle that 55mph was the windows down vs. A/C breaking point. Under 55 its best to go windows down. Above its best to go windows up with the A/C. But i believe they were using a large SUV.

 

Keep in mind that mine is a 2.3. Yes back to back A/C vs no A/C there IS a difference-at least on mine.

 

having the AC on with my manual 2002 GT makes my rpms go up at idle while coasting and dont drop until i roll to a stop

 

I've personally pulled 38.8 mpg out of my stock C5 M6 Corvette. I did it on a trip from FL to OH, some 600 miles if memory serves. I kept the car barely above idle cruising at 45-55mph. I used only the vents, not the A/C. Windows up. I kept it in 6th gear for as much as possible. I took advantage of downhills that were steep enough to maintain speed by going into neutral. I keep tire pressure between 32 and 35 psi. I drafted briefly a couple of times, but mostly found that the speeds I had to go to draft actually ended up costing me fuel efficiency rather than slowing down to 45-55 mph and driving on my own. Keeping it in that range was actually better than the overall average, but I got bored a few times and sped up to 70.

I used the displayed MPG and also used the pump and odometer. The only way I could have been off is if the odometer itself is off. What the pump calculation returned was actually higher than the Vette's "Driver's information center," which reported something like 36.x mpg.

A/C definitely drags down fuel efficiency by a couple mpg, at least in my own testing.

 

People also don't realize that driving with your heater control knob on defrost all the time.. Runs the compressor...

Those who don't like air/heat blowing on their face, and direct it up to the dash (defrost) are getting less fuel economy all the time.

Like Todd stated, tire pressure is key. I run my high MPG car at 38-40psi cold. A solid 1-1.5mpg difference recorded from 32. A belted radial will not wear more in the center this way. That speech was from the 60-70's when tires were Bias-ply!!!!!! The ONLY thing you give up when running higher pressures is slightly harder ride quality. It's not even that noticeable unless you go over 40psi. There's a TON of good info on tire tips and technology out there for better MPG's.

A vehicle with a recommended pressure of 35 psi whose tires are at 28 psi will have increased its rolling resistance by 12.5%.

 

A couple words on safety... Don't turn your motor off while coasting downhill. The only way that is a "win" is when it's in "DAR-win".

The tire pressure listed on the side of the tire is for when the tire is cold. Don't worry about when the tire heats up, that's factored into the recommended cold pressure.

The stock tune on a 4.6 4v has stochiometric AF below 2k rpm, then gets richer.

Turning on the AC causes the idle speed to bump up 40 or so rpm to preclude stalling.

The guys on the 94/95 forum assure me that coasting with the engine running is less fuel efficient than leaving the thing in gear and engine braking... evidently the motor shuts the fuel off completely but the engine continues to turn from the car's momentum. Consult your engine's programming.

Supposedly using AC with the windows up on the freeway gives better mpg than lowering the windows and not using AC. It is claimed that the increased drag of open windows is greater than the increased drag of the AC compressor. Beats me which is true.

 

Yes the injectors do shut off when you're coasting down hill in gear. It's called "over-run fuel cut". If you throw the car in neutral coasting down hill, you're losing MPG.

The Mythbusters windows vs. A/C thing was tested with some Ford Explorers if I remember correctly. And it was something like 55 or 60mph where A/C was more efficient than windows down.

 

I'm not going to argue the point, but I definitely believe that from an efficiency stand-point, you're better off coasting in neutral than slowing down the car due to engine compression. Maintaining or gaining speed is preferable to putting a decelerative force on the car. If you're trying to regulate your speed, then DFCO is certainly logical.

Chris

 

Big brick Expeditions
MythBusters: Air Conditioning vs. Windows MiniMyth : Video : Discovery Channel


To address the injector thing. It may cut them off as you are in gear with your foot completely off the pedal BUT the engine is now slowing you down with its compression. For fun I slow down in gear and let the engine gargle down instead of using my brakes. SO it may be using less fuel but you are now slowing down instead of coasting. And therefore you've just wasted the gas you used to accelerate up to speed with. Kind of counter productive.

 

I believe the example given was coasting 5.2 miles straight downhill. The car isn't going to slow down much in an overdrive gear.

That way toddturbo can turn off his injectors but without needing to do something stupid for him and everybody else like turning off the engine on a public road.

 

From what I have read and understand, the Fox Mustang's computer has DFCO (Which is Deceleration Fuel Cut Off) however, it does not activate quickly enough (it takes 31 seconds) to make a real difference in street driving.

The 94-95's may have this enabled to be more useful. I know that the 1993 Cobra computer DID utilize the capability in a faster way than the 87-93 5.0 GT and LX cars.

http://forums.corral.net/forums/lounge/1287750-coasting-gear-mpg-question.html

Read this thread I started a while back, I was curious about DFCO as well.


As far as whether or not it makes sense, I think it just depends on what you are doing. For instance, if you are coasting to a stop sign or stop light, then you should certainly stay in gear until you have to clutch in to keep from stalling because you are coming to a stop anyway.

If you were coasting down a hill, however, it may make sense to get into neutral because you could stay in neutral coasting longer than if you stayed in gear coasting. Unfortunately, the only way to KNOW which is more efficient would be to have a way of testing how much fuel is used over a given distance using both methods.

I have a feeling that it is probably almost a wash whether you put the car in gear or coast at this point, so you probably are just as well to leave it in gear.

 

I did some research on tire/wheel weight. Well... intraweb research.

Wheel Tech - Road Wheel Weights Can Affect Your Vehicle's Show...and Go

A narrower tire got significantly better fuel economy in stop and go driving... even though it was heavier than the lighter tire/wheel combo.

 

That link isn't going to any sort of article.

 

something else with drafting, if you can travel on roads with high close side walls or close heavy vegetation you can draft in a pack and greater distances. The wind created by the packs of the cars travels more in the direction you are traveling. If there is nothing on the sides of the roads you have to closer to preceding traffic to get any drafting effects. I've noticed it on 95 where the trees are real close to the road.

With today's A/C compressors pretty sure all vehicles do better with the windows up and A/C on as opposed to windows down (at highway speeds). Also, when ever I going to press the gas I cycle the A/C off, and try to have it on only at steady state or decel.

I would think if you are coasting down a hill engine braking you'd end up slowing quite a bit more than being running in neutral. I understand the injectors are off downhill, but you have to speed back up after the engine braking and burn more gas than you saved. In neural you'll probably speed up and can bleed the speed off on the back side prior to putting it back in gear. It be a trade off in the burn rate at idle compared to the fuel required to get back up to speed. (and whether or not you can afford to speed up in neutral).

 

I'm not assuming everybody is an idiot, and that the driver can use some common sense. If the grade is so shallow that you're slowing down in gear, by all means go in to neutral.

I live where there are hills that you can roll down in overdrive, with the injectors off, and the car will still accelerate through the engine braking. You need to supplement engine braking with brakes, or downshift in order not to reach speeds that will get you arrested for reckless.

So to simplify. Rolling down hill in neutral and maintaining speed with your brakes, is worse for your MPG than rolling down hill in Overdrive and letting engine braking keep your speed reasonable.

 

I'm not assuming everybody is an idiot.

maybe not everyone but a few, people claim you can use water feasibly as fuel (the previous hydrogen post)

I don't think it was really put into context; I understand what your are saying, but living on the east coast or gulf coast my entire life all the grades are pretty shallow. I think the I-10 bridge over the Mississippi would apply to engine braking with the injectors off, but otherwise the grades are pretty shallow. I based my assumptions on the driving that I do. If I am trying to save gas I'll maintain a constant RPM up hill even if I decel, then coast down in neutral. None of my hills will get much over the speed limit after the slight decel going up hill. Also, I think the amount saved is very negligible in my case. I was happy with 10mpg today in my race car (that I has tags and I drive on the street). Last time it was 8.

 

I'm not assuming you're an idiot, either, but have to respond to the words you post, not what your intent is/was since I can't read minds.

As a point of clarification, even if your car is accelerating going down hill, it's best to let it coast unless there is a reason to regulate vehicle speed. i.e. there is no danger or legal reason to prevent the acceleration of your vehicle.

I'm sure it's only a small amount of fuel savings, but after you put it all together: air in the tires, not running the a/c compressor, coasting when able, leaving the windows up, not running the lights, accelerating moderately to your final drive gear when able, not accelerating uphill, not going too fast for your car's peak efficiency window etc... it all adds up to fuel mileage that a lot of people won't believe. You wouldn't believe how many people have challenged me on the fact that I pulled 38mpg on a 600mile trip in the corvette.

 

FastDriver: Coasting down a hill is the only disagreement. Evidently is better to do it in gear. Near Grapevine, Ca coasting in neutral supposedly gets the cars going 90mph, so engine drag would reduce the cost of one's speeding ticket while making Planet Earth just one little bit greener.

 

Exactly.

That was not a disagreement with my statements:

As a point of clarification, even if your car is accelerating going down hill, it's best to let it coast unless there is a reason to regulate vehicle speed. i.e. there is no danger or legal reason to prevent the acceleration of your vehicle.

Some of these methods posted I have to disagree with or just call stupid. Shutting your car off or shifting to neutral to coast down hill are both illegal because they are dangerous. You do not have full control of your vehicle only a misperceived partial control. If you do either of these during a road test for a license you will fail instantly.

No, you haven't lost control just by shutting off the engine, shifting into neutral is certainly not illegal, and doing either is not necessarily dangerous. If your opinion differs, please expound upon what control you believe has been lost by going to key-on-engine-off. I don't proclaim that shutting the engine off is the most intelligent idea, but it certainly has merit. Personally, I don't like the added wear on the starter or clutch, but if I'm coasting to a final halt, say to my driveway downhill for the last 1/4 mile of my drive, then I have no issue with shutting down the motor.

The only thing you lose is the ability to accelerate, which is not dangerous, and power assisted steering, which is not to be confused with a loss of steering. You even still have brake-boost assisted braking.

 

Exactly.

 

Does anyone skip gears? I have no documented tech that it works. Sometimes I go 1-3-5/6 or 1-2-4-6

 

Chevy forced 1-4 shifts on T56 fbodys under certain conditions in order to meet either emissions or fuel consumption requirements.

I'm not exactly sure what those conditions were, b/c I've never owned one but I think it's under light acceleration. I know the chevy guys sure bitch about it a lot.

 

Yes, my friend's 98Z28 had the skip shift. There's easy fixes for that. Either a paper clip jumper or another you can buy. Although it was weird, the car still drove smooth. I tried going 1st to 4th when my car was stock, and it didn't like it very well. Just more low end torque in those LSX motors.

 

Some of these methods posted I have to disagree with or just call stupid. Shutting your car off or shifting to neutral to coast down hill are both illegal because they are dangerous. You do not have full control of your vehicle only a misperceived partial control. If you do either of these during a road test for a license you will fail instantly.

Along the lines of acceleration I have found in some vehicles it will be better for mpg to accelerate briskly (3000 rpm shifts) instead of granny accel(2000 rpm shifts). This will depend on gearing as the low rpm may not be up to the power band. Under the power band during acceleration is not as efficient. I have had a 5.4 f150 lifted running 4.56 gears and 38 inch tires get better mpg than 3 coworkers with their stock 4.6 f150s of same years. My 91 cherokee averaged better than 2 other coworkers could with theirs. My mustang was used to test my acceleration theory of mpg on numerous tanks of fuel. The restraint to go slow was difficult and after seeing my mpg diminish I went to a higher shift and watched the mpg return.

 

All above was TLDR. So I'd like to give my input on the OP. In my GT and Cobra, I have to at least wait 'til around 2,500 to shift. If you shift and 2,000, does it seem to bog anything down? If so, for the sake of the car, bump it up a little. Try 2,250 and keep going up until the car isn't bogged down. I did this with the Cobra due to its piss poor MPG and the prices of premium always suck ass.

Every 3,000 miles, a nice check-up (i.e. check the air filter, pull a spark plug, go check your car for codes... Those all could help gas mileage... A happy car is a healthy car.

 

Been piloting vehicles around for a bit over 4 decades now. I wouldn't ever recommend slipping the car into neutral unless you're stopped. Sometimes the safe path to avoid an accident when the unexpected occurs is to step hard on the brakes. However, there are just as many occasions where the safe path out of the unexpected involves stepping hard on the gas pedal ---- doesn't do much for you when the car's in neutral --- so you've actually lost a very important measure of control when you slip it into neutral while on the move. You really learn a lot about this if you've ever spent quality time road racing and at road racing driving schools. And the thing about the UNEXPECTED is what should be obvious -- you never know when it's going to strike. The time it takes to get it back in gear can be the difference between an accident and a near miss; literally life and death.

I've monitored the number of milli-seconds the injectors are open under lots of different conditions in a couple of different vehicles. As one data point, in one my WRX's -- the injectors were open 2.6 ms at idle and 0.8 ms with the throttle closed decelerating in gear. THREE times LESS fuel decelerating in gear than coasting. If you want to understand how your vehicle is behaving under light load conditions (down a slight grade at speed) with the throttle barely open, closed, coasting (at idle) -- you really need to see what the injectors are actually doing. Different systems have different protocols -- it's not something that can necessarily be generalized from one vehicle to another. In any event - in my experience there is very little to be gained in this particular area of hyper-miling (coasting vs. very light application of throttle to maintain speed). The big hitters on the highway are simply reducing speed (see our Corvette mileage champion's post) and taking advantage of the draft created by others. And you don't have to drive at an unsafely close distance behind them to take significant advantage of the 'draft'. The big hitters around town are driving in a way that you can minimize or avoid stopping --- and not ever being in a hurry to accelerate. The people that get the best mileage around town are the same people whose tires and brakes last longer than anyone elses. Everything else is nits and nats. You need to tend to alignments, tire pressures, etc. if you're going to get all there is to get -- but the incremental gains in those areas won't be big.

Lastly I'll throw a plug in for reducing pumping losses in city driving. If you drive a big engine car or an automatic tranny, not much you can do about this. But a small engine and a manual enables you to short shift and do as much of your acceleration as possible in the HIGHEST gear possible with the the throttle WIDE OPEN. Not a typo. I'm talking 6th gear in the Mini at 1500 rpm and the pedal on the floor. You barely accelerate. With knock sensors - there's no detonation and no lugging. And, most importantly, the engine is working a bit like a diesel -- with the throttle wide open it's as if there's no throttle - and hence no pumping losses. If you have to accelerate anyway - if you can do it with no pumping losses, you'll do it using less fuel. It works. But not with automatics, and not with big engines capable of accelerating the car quite quickly even in the higher gears. BTW - this is the reason for the skip-shift feature on Camaros and Corvettes -- it was used to help the car be certified with a higher CAFE fuel mileage rating. As enthusiasts it drives some of us crazy. But it saves fuel.

 

But a small engine and a manual enables you to short shift and do as much of your acceleration as possible in the HIGHEST gear possible with the the throttle WIDE OPEN. Not a typo. I'm talking 6th gear in the Mini at 1500 rpm and the pedal on the floor. You barely accelerate. With knock sensors - there's no detonation and no lugging. And, most importantly, the engine is working a bit like a diesel -- with the throttle wide open it's as if there's no throttle - and hence no pumping losses.

Interesting.