My quest for 30 MPG - Ford Explorer Gas Mileage Tips

[gavin]

ya we are past that.... its been said that 3.73 give you better mileage running at 70mph and 2300 rpms but leaving the trans in OD while cruising 55-60 your rpms will be much lower and from the logic found here you would get better mileage taking it out of OD at those speeds...

but the truth is you will get better mileage at the lesser speed and at the lower rpm range.

lower RPMS =/= better MPG.

 

[SLVRTRC]

they by your logic if you were to run that explorer at 55-60 you should take it out of OD to keep your engine running at those speeds at its highest efficiency level.

higher speeds = higher rpm
higher rpms = engine using more fuel and air
gearing is not relative in this argument if you are going to say that you get better mileage with your 3.73 at 70mph running your 2300rpms but when you drive 55 your engine is producing less rpms and is using less fuel.

look what you have to do when you make any engine accelerate you give it more fuel more air. you can have a gas lawn mower and when you throttle up you give the engine more fuel and more air thats the basics of an internal combustion engine more fuel and air and at the right time a spark you make more power more rpms. You cant tell me that engine running at 2300 rmps uses less than if it were running at 1800 rpms.


yet another article http://www.metrompg.com/posts/speed-vs-mpg.htm

 

[jd4242]

wow i dont want to get into the last couple post but i would like to know what mpg are you running at now al?

 

[inh]

You do not gain fuel efficiency at lower speeds because you are at a lower RPM. That is a contributing factor, but a very minor one. The mileage increase is from wind resistance, which increases exponentially with speed.

 

[SLVRTRC]

You do not gain fuel efficiency at lower speeds because you are at a lower RPM. That is a contributing factor, but a very minor one. The mileage increase is from wind resistance, which increases exponentially with speed.

get in your truck and start it up see where it idles at then put your foot into the gas petal and watch your tach go up.

more rpms = more gas

 

[Maniak]

Thats an over-simplication of fuel usage based on rpm.

Think of it this way.. Your driving at 1500 rpms on the freeway with the throttle open 20% of the way.. Now the wind starts to blow and you have a headwind. You now have to hold the throttle open more (say 50% of the way) to keep the same rpms.. Your using more fuel, but not using any more rpms...

Its a combination of throttle position (fuel trim), and rpms.. But.. by increase the speed you are exponentially increasing the load the engine sees due to wind resistance which means you need more throttle to hold the rpms than you would if you were at those rpms in that gear at a lower speed.

~Mark

 

[gavin]

right.

so if you claim (not saying you dont) to get 30+ mpg @70mph with 3.73 and OD and run at 2300 rpms.

this being so... you should get 35+mpg at 55. possibly better

Automobiles are most fuel-efficient between 45 and 60 mph. Large trucks lose fuel efficiency over 50 mph.

At 65 mph you're burning 10% more fuel than at 55, according to the American Council for an Energy-Efficient Economy. At 70 you lose 17% of your fuel economy, and at 75 it’s 25%. The numbers get worse from there.

Read more: http://www.thedailygreen.com/going-green/tips/best-gas-mileage-drive-55-461130#ixzz0Jq80g8Gn&C

FYI, I do believe you basically contradicted yourself posting this link.

don't you notice how mpg goes up, then back down in these graphs?

is this not enough to prove to you that less RPMS =\= better MPG?

If less RPMS = better MPG then a graph would bounce consistently up and down, NOT a single incline, peak, and decline.

now, in a perfect world, on a stationary vehicle (or on the moon, where there is no wind resistance), then yes, lower RPMS = MPG.

But see... we're talking real world here, not theoretical, or "perfect world" examples.

There's a difference.

 

[SLVRTRC]

FYI, I do believe you basically contradicted yourself posting this link.

don't you notice how mpg goes up, then back down in these graphs?

is this not enough to prove to you that less RPMS =\= better MPG?

If less RPMS = better MPG then a graph would bounce consistently up and down, NOT a single incline, peak, and decline.

now, in a perfect world, on a stationary vehicle (or on the moon, where there is no wind resistance), then yes, lower RPMS = MPG.

But see... we're talking real world here, not theoretical, or "perfect world" examples.

There's a difference.

how is that contradicting myself when the graphs show less mileage at 60+mph. when every time i mention that less rpms bruns less fuel you state that you need more power to maintain speeds of 70mph because of wind resistance ect and if you were to cruise at 55 you will use less gas do to the fact of less resistance and fewer rpms. If RPMS were not a factor you would run the truck OUT OD at 55 keeping your RPMs the same and in your power band.


no way am i saying that 30mpgs is not possible with the rig... im saying if it is true. Then by slowing down to 55 you will be fighting less wind need less power to maintain speed. That being so you should be able to swap in the 3.55s and have no performance problems and should be knocking on 40mpgs door

Thats an over-simplication of fuel usage based on rpm.

Think of it this way.. Your driving at 1500 rpms on the freeway with the throttle open 20% of the way.. Now the wind starts to blow and you have a headwind. You now have to hold the throttle open more (say 50% of the way) to keep the same rpms.. Your using more fuel, but not using any more rpms...

Its a combination of throttle position (fuel trim), and rpms.. But.. by increase the speed you are exponentially increasing the load the engine sees due to wind resistance which means you need more throttle to hold the rpms than you would if you were at those rpms in that gear at a lower speed.

~Mark

ok there is an explanation can i understand.

but i have noticed that anytime that i accelerate into a head wind or to a higher speed i needed more throttle and in relation more rpms to maintain speed and resulted in less mileage.

 

[aldive]

You do not gain fuel efficiency at lower speeds because you are at a lower RPM. That is a contributing factor, but a very minor one. The mileage increase is from wind resistance, which increases exponentially with speed.

So very true.

 

[rileyrs]

al, have you ever considered a body kit with lower bumpers, to improve wind resistance on your highway trips?

 

[aldive]

al, have you ever considered a body kit with lower bumpers, to improve wind resistance on your highway trips?

I will consider most anything.

Is there such a kit?

 

[SLVRTRC]

You do not gain fuel efficiency at lower speeds because you are at a lower RPM. That is a contributing factor, but a very minor one. The mileage increase is from wind resistance, which increases exponentially with speed.

So very true.

then why would 70mph be optimal

 

[rileyrs]

I will consider most anything.

Is there such a kit?

i was browsing and ran into this http://www.andysautosport.com/ford/1995_2000_explorer/exterior/body_kits/xenon/

then i realized you already had the EE air dam so this would probably be of no help since its similar.

what about the fiberglass cowl induction hood from EE, not so much for airflow, but maybe to loose a little weight, also it might help with cooler running temps.

a lighter truck should make a difference in mileage right?

 

[Carguy3J]

Because numerically lower gears require more torque from the engine to maintain speed, requiring you to use more throttle.

Well 1st, numerically lower gears will require more torque input IF you are traveling at a speed which causes the engine to be at an RPM below peak torque. However, if you make proper use of those numerically lower gears, and simply travel a bit faster, maintain a speed which puts the engine at peak torque rpm, then your statement is no longer correct. In other words, while Al's vehicle (w/ 3.73's) may be most efficient at a particular speed; all else remaining equal, if he were to simply swap to 3.55's, his most efficient speed would be higher. ( whatever increase in speed that would put is motor back at the same "most efficient" rpm he was at with the 3.73's)

I think, people frequently forget to take into account the fact that 1.)every vehicle is different, and will therefor require different techniques/adjustments/strategies to achieve the same goal. 2.) Where and when you drive IS a significant factor (road condition, traffic patterns,etc.) 3.) don't believe everything you hear from the government and "experts"

Also, geting back to your comment regarding "more throttle"; useing more throttle is NOT automatically less efficient. In fact, it's frequently the opposite. This is why one of the "secrets" that Al hinted at in a previous post works. I'm referring to increasing EGR flow. Why does it improve fuel ecnomy under cruise? Well 1.) it cools the air/fuel charge, lessening the chance of detonation. This allows for more advanced timing, and contributes to a more complete burn of the air/fuel charge. Since it is diplaces some of the air/fuel charge (w/ partially burnt exhaust gases), you have to supply the engine with more air to compensate. This means giving it "more gas" (not really, just a greater throttle angle or opening) In other words, you have to press further on the pedal for the same power output as w/o egr. Why is this good? Well, remember that an engine is an air pump. A more open throttle (w/o an increase in power output) results in less restriction, less parasitic pumping losses, and a more efficient engine ( at the cost of power production, which is why it only works at light load cruise) This is a big part of why diesels are so good on fuel (no throttle body/plate at all!)

comments / discussion ????

 

[Carguy3J]

MPG is not everything!

My standard driving is cruise set at 53 mph and get 24-26 mpg on level ground on a calm day.

Seriously????

Unless you are experiencing some kind of mechanical problem, that is extremely dangerous and down right rude. ( I'm assuming you are referring to traveling on the highway,at these speeds. Interstate highways are a minimum of 55mph, and many are 65mph or 70mph.

I don't care if it gets you 100mpg, you are a serious threat to safety on the highway at this speed. :roll: Speed itself is not nearly as dangerous as DIFFERENCES in speed. It has been my consistent observation that the general driving public has a very poor ability to judge closing rates, and said differences in speed between themselves and other vehicles around them. YOU NEED TO KEEP UP WITH TRAFFIC, AT LEAST!

 

[CDW6212R]

Very well said in the post two before this, I agree with 99% of that. Most people refuse to analyze what is happening inside an engine well enough to conceive of these ideas, let alone understand them. If it isn't written in a book, then the sun doesn't rise. Regards,

 

[Carguy3J]

More than aero

then why would 70mph be optimal

While aerodynamics do play a role, I don't think drag is so great at 70mph-ish that it overrides mechanical efficiency.

So, to answer your question, 70mph may be optimal for some vehicles, while others will be most effcicient at 55mph, 62mph, 79mph, or 90mph,etc..... Excluding extreme cases, the most efficient speed for any vehicle, in terms of sustained highway cruise, will be the speed (in top gear) that results in the engine operating at peak torque. At this engine rpm, the engine is it's most efficient, and this is the speed at which you can "float" the throttle to maintain speed. ( you are essentially limiting power output to a small fraction of the engine's potential at this point)

Final drive ratio (differrential gear x top gear trans ratio x tire diameter) will determine what speed is needed to maintain peak torque rpm. If this speed is undesirable for one reason or another, then you need to make appropriate adjustments to one of the three factors, to maintain rpm, while adjusting the target speed to what is desired.

 

[CDW6212R]

You are almost dead on with that. The part that isn't quite accurate(1% I was referring to before), is the point of maximum torque.

The best fuel mileage isn't going to be at exactly the maximum torque rpm, it will be at some point not far below that. Let's not nitpick, the concept is correct. It's just a slight matter of a different lower rpm than the max torque. As the gearing or other parts change, that magic speed does change slightly.

Al may be able to show several actual dyno tests of his truck, and results of his mileage testing. He can say from his testing where his maximum torque is for his SOHC, and the rpm where his best mileage comes at. The two are not the same. Regards,

 

[SLVRTRC]

pictures were taken on the same stretch of highway 80* flat for 2 miles with a tail wind. I rest the mileage each time on the flat while cruising.

 

[CDW6212R]

Please do not rely on the message center information as accurate fuel data. I have owned several Lincolns with the message center, and two Explorers/Mountaineers with it. That is not accurate, it's not even close.

Fuel mileage data must come from longer distances than a mile or two. The only real reliable fuel data is what you get from multiple tank fill ups.

Shoot, I've gotten 28-30mpg going to work in my Mark VII tons of times. Never mind that it's a downhill section and the message center is in error in those light throttle conditions. My real mileage with that car was about 18-21mpg, as documented by recording all fuel tank fill ups and mileage.