Originally posted by donwhite
2) Overinflate your tires, 45 psi in front, 40 psi in the rear. Natch, pump up your spare to 45 psi and let out the air if used on the rear.

Bad idea. Overinflating your tires reduces road contact area which can easily result in a loss of control during emergency cornering, high speed turns, and wet weather. This can be especially dangerous on snow and ice.
Stick to the factory recommended pressures, and make sure you read the pressure when the tires are cold.

3) Open your windows and turn the AC to “OFF.”

This depends on your speed. Having the windows down increases drag. At low speed the extra fuel needed to counter the drag is less than the fuel needed to drive an A/C compressor. At high speed the drag is much greater and it is more economical to use the A/C.

4) If your car runs a 195 deg thermostat, replace it with a 205 deg. If already at 205, then maybe the bold will go to a 215 if available.

This depends entirely on the motor. Generally it is a good idea to keep the motor at the factory set operating temperature.

5) Refuel daily. Calculate - unless your car has an electronic calculator - how much fuel you use daily, add 2 gallons reserve, and keep that amount in your car, saving perhaps 10-12 gallons of fuel being hauled around unnecessarily. 75 pounds more or less.

Minimal gains. Do it if you want, but 75lbs only uses about 1HP.

6) Use your cruise control every time you can. Set it for 5 mph UNDER the posted limit.

Depends on the vehicle. Trucks and SUVs are high drag vehicles and have best fuel efficiency at lower speeds. Sports cars and other highly aerodynamic vehicles can obtain optimal economy at higher speeds.

10) Use 100% synthetic oil and

If your car has never used synthetic oil, and you have over 60,000miles, do not switch to synthetic. Synthetic will easily leak past carbon deposits and other contaminates that have built up around oil seals, which in many engines are the only thing keeping the seals from leaking. Only switch to synthetic on newer vehicles and only after breaking in the motor with dino.

posted by apc

“Overinflate your tires, 45 psi in front, 40 psi in the rear.” Bad idea. Overinflating tires reduces road contact area which can result in loss of control during emergency cornering, high speed turns, and wet weather. [Edited by Don W]

Tire patch is the measure of friction. Directly proportional. On the theory that people primarily interested in higher MPG will not be operating the vehicle at its limits, I again suggest higher pressures will improve MPG.

“ . . turn the AC to “OFF” This depends on your speed. Having the windows down increases drag. At low speed the extra fuel needed to counter the drag is less than the fuel needed to drive an A/C compressor. At high speed the drag is greater and it is more economical to use the A/C.

No argument here on drag. I personally believe air drag up to 35 is negligible. From 35 to 65, my recommended top speed, there will be more drag with windows down. Perhaps raising the windows and using the car’s VENT feature will produce satisfactory results?

“ . . a 195 deg thermostat, replace it with a 205 deg.” This depends entirely on the motor. “Refuel daily.” Do it if you want, but 75lbs only uses about 1HP

Higher operating temperatures should produce more thermal efficiency in the engine’s operation.

“Use cruise control . . Set it for 5 mph UNDER the posted limit.” Depends. Trucks and SUVs are high drag vehicles and have best fuel efficiency at lower speeds. Sports cars and other highly aerodynamic vehicles can obtain optimal economy at higher speeds.

“Efficiency” and “optimal economy” are not the equivalent of actual consumption. That is the bottom line here. It takes less heat to move any vehicle at 35 mph than it takes to move the same vehicle at 70 mph. Heat equals fuel. Less is better and “efficiency” and “optimal” do not enter into the equation.

“Use 100% synthetic oil . . “ If your car has never used synthetic oil, and you have over 60,000miles, do not switch to synthetic. Only switch to synthetic on newer vehicles and only after breaking in the motor . . “

Good advice.

Originally posted by donwhite
Tire patch is the measure of friction. Directly proportional. On the theory that people primarily interested in higher MPG will not be operating the vehicle at its limits, I again suggest higher pressures will improve MPG.

Higher pressures maybe in direct relation to the factory recommended pressures. You can not quote "Use 45psi on the front and 40 on the rear" to someone running 30" or larger tires. That would most likely push the beads to their limit and cause failure at high speed, probably resulting in death.

Safety is the primary concern when operating a vehicle, not fuel efficiency. Use the factory recommended specs as long as you are using factory recommended tire dimensions. The engineers who came up with the numbers know what they're doing. Unless you have considerable education to surpass their judgment, trust theirs.

No argument here on drag. I personally believe air drag up to 35 is negligible. From 35 to 65, my recommended top speed, there will be more drag with windows down. Perhaps raising the windows and using the car’s VENT feature will produce satisfactory results?

Well, if the temperature is 80+degF and the dewpoint is over 70, using the vent only will just turn your mobile greenhouse into a well ventilated mobile greenhouse.

But there are some cars who experience optimal fuel efficiency at 80MPH. The Nissan 300ZX circa 1988 comes to mind. Again it comes down to the aerodynamics and weight of the vehicle in question. A 4500lb SUV going 75MPH will get far worse fuel economy relative to the motor displacement than a 3000lb sports car traveling at the same speed relative to displacement.

Higher operating temperatures should produce more thermal efficiency in the engine’s operation.

Again it depends entirely on the motor in question. Some like to run cool. Others like to run hot. Unless you are well educated in the thermal operating ranges for your specific motor, compression, and fuel needs, it is best to stick with the factory specs.

“Efficiency” and “optimal economy” are not the equivalent of actual consumption. That is the bottom line here. It takes less heat to move any vehicle at 35 mph than it takes to move the same vehicle at 70 mph. Heat equals fuel. Less is better and “efficiency” and “optimal” do not enter into the equation.

Uhm... maybe you should look up "efficiency" and "optimal" in the dictionary.

The bottom line is if you want to get significantly better fuel efficiency, buy a car with a better rating. There's only so much you can do to a motor that has received a specific rating, and most of the options do not pan out in the end.

The only truly practical and economical way to improve fuel economy on an existing vehicle is to adjust driving habits. Drive like your brakes are going to give out... milk inertia for all it's worth.

I have to agree. To get the best mpg you can only tweek so much. If you are interested lowering your gas consumption you have to downsize and change your driving habits a bit as well.

Now a small car may not be practical for all everyone for any number of reasons.

What you need for maximum mpg IMHO. A plug in hybrid with a diesel engine. There are plug in Prius's that are getting close to 100 mpg in city driving (They enlarge the battery pack and you can plug the car in to charge it) the engine only comes on over 35 mph. SO in Los Angeles where they are based, they spend alot of time in traffic.)



[edit on 5/4/07 by FredT]

posted by apc

You cannot "Use 45psi on the front and 40 on the rear" to someone running 30" or larger tires. That would push the beads to their limit and cause failure at high speed . . Safety is the primary concern when operating a vehicle, not fuel efficiency . . [Edited by Don W]

Between the lack of refinery capacity here, and Hugo Chavez there, the current near $3 gasoline may look cheap before year’s end. For example, I share ownership in a 2nd house some 275 miles from my primary residence. I’m fortunate that even $4 gasoline is more a political issue than an economic one for me but many people are not so well placed. I was alive and well during the Great War, WW2. We had a well observed 35 mph national speed limit. The base “A” gas coupon got a mere 3 gallons per month allotment. Everyone I knew about over-inflated their tires with little adverse consequences. You do what you have to do.

If the temp is 80+ deg F and the dewpoint over 70, using the vent will just turn your mobile greenhouse into a well ventilated mobile greenhouse.

Undeniable. But I’m addressing the issue of increasing the MPG of existing vehicles.

There are cars that experience optimal fuel efficiency at 80MPH. The Nissan 300ZX circa 1988 comes to mind. Again it comes down to the aerodynamics and weight of the vehicle in question.

When you compare rate of consumption to rate of progress, it may well be that by varying drive axle ratios, tire size as well as using overdrive transmissions, one might correctly say Car X is “most efficient” at this or that speed. Which is ignoring the simple fact that at the higher speed Car X is consuming more fuel and not less fuel than at a lower speed to cover a specified distance. My approach is to achieve point A to point B travel using the fewest gallons, regardless of “efficiency” or “optimal” conditions. You may be including "time" in your equations whereas I am not.

posted by FredT

I have to agree [with APC]. To get the best mpg you can only tweak so much. If you are interested lowering your gas consumption you have to downsize and change your driving habits a bit as well. What you need for maximum mpg IMHO. A plug in hybrid with a diesel engine. There are plug in Prius's getting close to 100 mpg in city driving (They enlarge the battery pack and you can plug the car in to charge it) the engine only comes on over 35 mph. SO in Los Angeles where they are based, they spend a lot of time in traffic.)

In batteries it is a law of nature, power is amps. But More Amps in any battery equals More Weight. At some point, the lines cross and you are hauling more weight in the battery than you are saving in the fossil fuel, whether in your own tank, or at some far off power plant.

I am not addressing which car now available or soon to be is the most efficient. I am offering ways to gain more MPG from your 5 years old clunker.

[edit on 5/5/2007 by donwhite]

Originally posted by donwhite
Between the lack of refinery capacity here, and Hugo Chavez there, the current near $3 gasoline may look cheap before year’s end. For example, I share ownership in a 2nd house some 275 miles from my primary residence. I’m fortunate that even $4 gasoline is more a political issue than an economic one for me but many people are not so well placed. I was alive and well during the Great War, WW2. We had a well observed 35 mph national speed limit. The base “A” gas coupon got a mere 3 gallons per month allotment. Everyone I knew about over-inflated their tires with little adverse consequences. You do what you have to do.

I'm not sure what most of that statement has to do with the issue of improving fuel economy on an existing vehicle.

If you suggest everyone blow their tires up to their max rated PSI and then never go over 35MPH... more power to you. But people will get even better fuel economy if they just got out and pushed.

When you compare rate of consumption to rate of progress, it may well be that by varying drive axle ratios, tire size as well as using overdrive transmissions, one might correctly say Car X is “most efficient” at this or that speed. Which is ignoring the simple fact that at the higher speed Car X is consuming more fuel and not less fuel than at a lower speed to cover a specified distance. My approach is to achieve point A to point B travel using the fewest gallons, regardless of “efficiency” or “optimal” conditions. You may be including "time" in your equations whereas I am not.

Your approach is too generalized. Super Aerodynamic Car X travelling a specific distance will use more fuel at a lower RPM, in a certain gear, at a certain speed, than at the same RPM, in a higher gear, at a higher speed. Total fuel used to travel a given distance is directly and inversely proportional to the rate of consumption, horsepower, gear ratio, and time spent over the rate of travel.

This is funny though. Reminds me of the old people driving episode of South Park.

Elderly Man: Damnit Mona, this isn't the fastest way to Country Kitchen Buffet!
Mona: No, but it's the shortest. I save the most gas that way.
Elderly Man: You save the most gas if you take the highway to Country Kitchen Buffet!
Mona: Less miles means less gas you old fool.
Elderly Man: There's Country Kitchen right there!

[edit on 5-5-2007 by apc]

Thread Topic: How to Increase MPG

posted by apc

I'm not sure what most of that statement has to do with the issue of improving fuel economy on an existing vehicle. [Edited by Don W]

I offered a personal anecdote to demonstrate that adding air to tires is not only an old practice, but one without the dire consequences you forecast.

If you suggest everyone blow their tires up to their max rated PSI and then never go over 35MPH . . more power to you . . people will get even better fuel economy if they just got out and pushed . .

Necessity is the mother of invention.

Your approach is too generalized . .

I think you are mixing “efficiency” and “optimal” with absolute consumption values. Both “efficiency” and “optimal” are relative terms, useless unless we know what the comparison is. Like the child’s “my father can beat your father.”

I, OTOH, am confining my recommendations to absolute terms; how to reduce the number of gallons consumed traveling from point A to point B. I do not need to know the relative “efficiency” of Car X, or the “optimal” values of Car Y when either is compared to yet another Car Z.

Originally posted by donwhite
I offered a personal anecdote to demonstrate that adding air to tires is not only an old practice, but one without the dire consequences you forecast.

If people die because their tires exploded on the highway because their T-speeds were reduced to 50MPH or if they slam into a concrete wall in a turn because the normally thumb-sized contact area between the tire and the concrete was reduced to the width of a pencil, all because they listened to the archaic anecdotes of someone on the Internet, I hope you are held accountable.

I suggest you do a quick Google search for "overinflated tires". Learn a thing or two, and realize that what you did sixty years ago no longer applies.

I think you are mixing “efficiency” and “optimal” with absolute consumption values. Both “efficiency” and “optimal” are relative terms, useless unless we know what the comparison is. Like the child’s “my father can beat your father.”

I, OTOH, am confining my recommendations to absolute terms; how to reduce the number of gallons consumed traveling from point A to point B. I do not need to know the relative “efficiency” of Car X, or the “optimal” values of Car Y when either is compared to yet another Car Z.

... yes, relative to the amount of a resource consumed over a given period of time. The comparison is one set of conditions on a specific vehicle compared to another set of conditions on the same vehicle.

Your recommendations are asinine, impractical, destructive, and risk serious injury or death.

Originally posted by donwhite
I offered a personal anecdote to demonstrate that adding air to tires is not only an old practice, but one without the dire consequences you forecast.

apc is not over exaggerating here. Over inflation of your tires may be an old practice, but that doesn't make it any better. They are many old practices out there that worked before, but can actually damage newer vehicles. Not only does over inflating decrease traction and stress the tire (which can lead to high speed blowouts i.e death), it creates abnormal tread wear and shortens the life of the tire. Which doesn't make people too happy after they've spent $500-800 on a good set. 40-45 PSI is way too much for 99% of most passenger tires, most of which have a maximum pressure listed on the tire itself of 35 PSI.

I worked at a tires shop for years and we could always tell when someone was over inflating their tires just by looking at them. Many of them came in because they tires had begun separating and were vibrating the drivers teeth out of their head.

Also, putting a higher rated thermostat doesn't seem like a good idea for me for two reasons. Mainly because the engineers who design these cars know what they're doing and design them to run as efficient as possible while still meeting emission laws. Also, raising the combustion temperatures of an engine produces more NoX, which is one of those nasty gases they measure when you go to get smogged. I'm not sure how high you'd have to get your coolant to actually effect combustion temperatures enough to raise your NoX levels, but I thought Id throw it out there anyways since its the first thing that popped into my head while reading your post.

How To Improve Gas Mileage

Heat is the great enemy of tires. Heat is generated at those 2 points in the tire’s circumference where it first contacts the road then departs from the road. At those 2 flexing points the tire ceases to be round and becomes flat. And forms the tire patch. Strengthen the tire and it will produce less heat as it rotates. Car makers - and their tire suppliers - want a soft ride more than long tire life. Or higher gas mileage.

Persons seeking to raise gas mileage are unlikely to be engaged in high speed cornering or hauling heavy loads at breakneck speed. Although I admit I have never tried this, I doubt the typical service station air compressor is strong enough to explode a new tire by overfilling.

Peace.

If the service station has an in-garage compressor, it is compressing usually to 125PSI.

Most people don't engage in high speed turns on the highway. Unless a deer runs out in front of them, someone elses overinflated tire explodes in front of them throwing the tread directly in their path, or some other emergency situation.

Cars aren't designed for optimal conditions. They are designed for worst-case scenario. Stick with the factory designs unless you know exactly what you're doing.

posted by XL5
What about adding O3 to the air intake from a small 10-25 watt ozone generator, making up 5-10% of the total air intake? [Edited by Don W]

I think O1, O2 or O3, it is the same in the combustion chamber. Or to put it another way, O is O. I think the problems with O3 advocates is they are right but only in a laboratory setting. Not in the real world because they cannot produce enough O3 to be useful. And O3, left to its own devices, quickly reverts to O2, the natural variety of O.

if you halve the weight of the car you need 4 times less power to get it moving at the same rate.

Sounds nice at first XL5, but it looks counter intuitive on reflection. I believe weight and power are directly related. Not inversely. The more of one, the more of the other, the less of one, the less of the other. In direct proportions.

Florida has a no price gouging law invoked in the aftermath of hurricanes. It has worked for the most part. Dire predictions of shortages by the anti-social free marketeers proved unfounded. When the retailers run out, they close. So far, the large suppliers have rushed extra goods into the state rather than close. I believe the law's application expires automatically after 60 days.

posted by newtron25

The material required to halve the weight of a car currently has many restrictions. Right now, composite fiber materials are still very expensive. It would be unlikely consumers could afford a "half the weight" car.

As for O3 adding to the engine, I think this is a great interim idea. The entire IC engine needs a complete redesign and nobody is stepping up to offer any real innovations, just micro-steps forward at a time is all I see. The latest design change to autos that got my attention was the CVT. This actually seems to promise more in potential savings than most engine improvements.

Other system wide tweaks are needed too such as regenerative braking systems, solar roof components, mixed fuel systems that are rely upon a very wide range of fuels, not just a narrow range of refinery based products. Just adding my 50 cent. [Edited by Don W]

Multi-port injection coupled with sensitive computers controlling the time for injecting as well as the quantity, has brought performance of the typical car’s engine in 2007 to a level never imagined in 1982, just 25 years ago. Prior to the engines of today, we said an IC engine was 25% efficient. I have not heard whether that number has increased or not, but surely if 25% was right in ‘82, it must be 40% or even 50% today?

[edit on 5/11/2007 by donwhite]

I agree with apc's posts regarding conscientious braking...

I'd like to add tailgating (as in NOT TAILGATING) so as to not have to be on and off the brake and gas as much, not to mention it's safer and you won't dick-up your hood or windshield as easily. Also using cruise control helps me max my mileage.

I also suggest using the terrain to your advantage.. Like if your coming up on the crest of a hill let off the gas before you crest, let momentum carry you over the top and gravity pull you down the other side.

posted by Stale Cracker

I agree with apc's posts regarding conscientious braking . . I'd like to add tailgating (as in NOT tailgating) so as to not have to be on and off the brake and gas as much, not to mention it's safer . . “ [Edited by Don W]

Given the opportunity, I have always driven as fast as I could. I like speed. It is pleasurable. It is (for me) irresistible. That is why I never bought a fast car. I harbor no death wish. A 350 Olds Cutlass was the fastest car I ever owned. Other cars I owned were, 3 Beetles, 2 English Anglias,1 Volvo 242, and various 302 Fords. The Olds maybe 115 mph, the Fords maybe 100 mph downhill. Because on American interstates you can frequently get away with 78 or 79 mph, I have many miles of VW time with the pedal to the metal. I said all that to explain that I have always been a keen observer of brakes and braking techniques.

As the IC engine is nothing more than a heat converting device - turning heat into motion - so also automotive brakes are nothing more than heat exchanging devices converting kinetic energy into heat.

Brakes unlike engines work best when cold. Or at least at the ambient temperature. Therefore, to bring a car to a quick halt from high speed, it is best practice to apply the brakes as strenuously as possible at the beginning of the deceleration maneuver. Never begin with the “light” tap and then gradually increase pressure. Although modern disc brakes are not nearly so susceptible to heat as the old time drum brakes, the bottom line is do your heavy braking when the system is cold or cool. Anti lock brakes take out most of the braking skills I learned over the yeas to the betterment of driving.

[edit on 5/11/2007 by donwhite]

If you need to use heavy braking, you have wasted your momentum, and therefore wasted the fuel spent to build that momentum. I reaffirm, drive like your brakes are going to give out, and you save significant fuel.

Driving in hilly terrain is a good way to note the use of momentum. You want your slowest speed to be at the tops of hills, and your fastest speed to be at the bottom. Tapering the throttle appropriately to achieve this result.

However donwhite, you are correct in your statement about high speed braking. It is best to apply the greatest amount of braking force at first when the brakes are cold, rather than when they heat up and start to fade. Although I'm not quite sure what that has to do with improving fuel economy.

>

Sounds nice at first XL5, but it looks counter intuitive on reflection. I believe weight and power are directly related. Not inversely. The more of one, the more of the other, the less of one, the less of the other. In direct proportions.

I'm afraid they are inversely proportional. This is a basic engineering principle called the Power to weight ratio. The formula for finding it is PtW = P/m, where P = engine power and m = vehicle weight. The higher the PtW, the better the performance. It should be obvious by logic anyway, but you can see from the formula that as m decreases, PtW increases.


[edit on 11-5-2007 by apc]

one thing that i dont think has been covered in this thread is tuning your vehicle. i had good results with only a rough street tune i did i went from roughly 270miles per tank to around 350 miles per tank in my car ad it runs sooo much better ive also tuned other cars as well!


www.moates.net < has things for tuning ford, chevrolets, HONDA's, and i think dodge's and they have great serivice!

Depends, and only as long as you stay naturally aspirated. But the cost of most modifications are usually greater than the average driver's fuel savings over three or four years. It costs about a thousand bucks to build up your typical low-end rice rocket. But there's plenty of little things for free you can do, especially on Hondas, that net one or two ponies. Plus, you only see gains if you don't change your driving habits for the worse (strong accelerations).