Picture of How to Become a Hypermiler
The best way to save on fuel is to not use it at all - ride a bike, use mass transportation, etc. However, there is a rather large subset of the population that live in a suburban prison. The following is a set of techniques used by people that call themselves hypermilers to achieve high fuel economy/efficiency (FE) numbers, save the planet and save their wallets.

Step 1: Tires

Picture of Tires
Inflate your tires to, at least, the maximum inflation pressure to reduce rolling resistance.

Should you wish to go beyond, that is up to you. Personally, I inflate my tires to around 55psi (they are rated for 44). Please do not attempt on old or visibly damaged tires. My tires are new and in excellent condition.

Modern tires are radially belted - that is, they won't balloon like tires of yore. Keep in mind what you're doing though. You are reducing the contact patch of your tires in order to decrease static friction. This will reduce your overall braking ability. So riding someone's bumper at 80mph is just that much more dangerous. Again, these steps only work when combined - you can't pick and choose.

When it comes time to buy new tires, look for low rolling resistance (RR) tires. While they may not have the same 60,000 mile (or even 40,000) guarantee, they will save you in the fuel department. The Toyota Prius comes equipped with LRR tires.
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jimmytvf5 years ago
yes, is effective in save money in gas, but it doesn't if you have to buy new brakes. is going to be more expensive the brakes than a few ml. of fuel.
trebuchet03 (author)  jimmytvf5 years ago
Don't brake during pulse and glide ;) This is a well documented driving technique.
i'm saying that because in downhill the engine make a little inertial brake, and if you turn off the engine, that inertial brake won't work and you have to apply more brakes. in flat surface will work good ;)
trebuchet03 (author)  jimmytvf5 years ago
It is quite possible to inertial brake with the engine off if you have a manual transmission ;)

Then again - on hills, I'd rather use my brake than use my engine as a brake. Brakes even have the name :) Needlessly having pistons slide in the head to slow down your car - it's much cheaper to replace brakes than rebuild an engine ;)

it doesn't really cause any wear on the engine to engine brake (the braking/energy losses is done through the compression of air in the cylinder, not the friction of the cylinders), plus modern engines cut fuel over a certian RPM while engine braking. so if you're going down a steep hill and you find you're having to use your brakes, just put it in gear and don't touch any of your pedels. Once it levels off you can go back into neutral.

jimmytvf5 years ago
I don't agree with the alternator feature. the alternator loads the battery, and doesn't need more power to drive all the electric features, the battery does the job as well. Yes, the faster the alternator goes, the more power generate, and goes to the battery.

It depends on the amperage of the alternator. Not the voltage or how fully charged a battery is. If the electronics are pulling too much amperage then the alternator turns into an electromagnetic brake and starts lugging the engine down.

My car now has a 70 amp alt. When my bass hits in the subs my headlights dim. My old car had a 120 amp alt (almost double the power output, not voltage) and the headlights never dimmed using the same exact system.

Its also the reason most cars are switching to LED. FAR less energy draw on the alternator to run them.

mrdoc jimmytvf2 years ago
Please don't spread rumors for what you don't know!

When the car is moving down the road the alternator runs ALL electrics in the car, AND recharges the battery. It ususally only takes a short time to recharge the battery, then that part of the alternators use is done.

The batteries sole purpose in life is to start the car. Once started you can remove the battery and car will run just fine and as long as you don't turn it off will run just fine for as long as you want!

UNLESS you've added additional electrics to the car, and I mean a lot of additional electric to the car, the alternator can power them just fine, there is no "big" load.

All the voltage generated that is not needed by the car/electrics are truned into heat and dissipated into the air. More speed does not mean more voltage generated, thats taken car of by the voltage regulator. The regulator keeps the top voltage output caped at 14.5 approximitely. After a few thousand rpms the output of the alternator does not increase, it stays constant. Same output at 30 as at 80mph.

trebuchet03 (author)  jimmytvf5 years ago
Generally speaking - the battery is only used while starting. Alternator output will match the load requirement from all electronics from the car. The alternator is capable of delivering more power at a higher RPM but will not deliver if the load does not exist.

A battery is not an infinite sink of energy storage. You can't add more energy to a "full" battery without damage. Grab an ammeter and measure yourself (I would recommend a clamp on inductive type rather than a shunt ammeter as the current flow during starting will be very high).

If you have the opportunity, I highly recommend auditing an introductory course on electrical engineering at a local university. Particularly lessons on Kirchhoff's Circuit Laws (loops and whatnot). I was Mech engineering but really loved the electrical engineering bits :)
that's what i wanted to say, when the battery is full, it have enough power to run any electric device you want, and doesn't mean any fuel consumption, because the alternator is always running. I'm spanish and i don't even know to express myself in some ways, and i'm a automotive technician and we learn Kirchoff's law too. Have to take a look, because i have some aspects that i don't remember, 3 years have been passed since that
trebuchet03 (author)  jimmytvf5 years ago
You're somewhat familiar, excellente! If we were to represent the vehicle loads (computers, lights, valves, etc.) as one single load for simplicity - we could draw the circuit diagram with three components in parallel. Those components are the alternator, the vehicle loads and the battery.

The alternator is source, the battery can be represented as a capacitor as it is near full and the loads can, for simplicity be represented as a resistor (lets not mess with inductance).

Before the car is started, the battery is around 12.5V

When the vehicle is started, current flows from the battery through the loads and bypasses the current source.

Next, the alternator takes over. The voltage off the alternator is higher than the battery (13.8-14.5V or so). Current flows into the load. Because the alternator's voltage is higher than the battery, current can also flow into the battery. As the battery voltage increases (as it will for this chemistry), current slows down until the voltage equalizes and current can not flow. This is why we can represent the battery as a capacitor. When a capacitor is fully charged, it is effectively an open circuit.

From this point on, current flows from the alternator to the load and bypasses the battery (as it is "open").

Now, an 80amp rated alternator does not always put out 80A. If the load only calls for 10A, the alternator only puts out 10A. We can not have this equation out of balance (energy in must equal energy out + entropy losses). Simply, the current that goes in must be consumed. When the car demands more current, the alternator supplies it and in turn the alternator requires more torque from the engine to turn.

More torque means more fuel consumption. With an instantaneous fuel gauge, this can easily be seen be comparing idle fuel consumption with little electrical load to fuel consumption with as much load as possible (high beams, defroster, vent fan without a/c, brake lights, hazard lights, power windows in motion, etc.)
The amperes become through the resistance of the material (more loops on the alternator), doesn't mean more torque. The engine has the same torque all the time (crankshaft, camshaft, and so on) are spinning with a minimum torque when it starts, the torque is only needed for the wheels to keep on the ground, excessive torque=wheelspining you don't want an alternator do this.


alternators work like engines, there's minimum friction, only for + and - contacts ( they have to spin to connect the wires obviously)

NOW, what you want to do, is turn, for example, water pump, fuel pump, the engine fan and so on, running electric, that will be less load on the engine and the alternator is capable enough to run all this elements, is designed for this use, A/C, the stereo, airbag control system, fuel injection... everithing is going with current nowadays and brands desing better alternators to handle up this loads. (Toyota prius, for instance, nuff power to pull out their own motors that are the alternators itselves)
I went driving one day in an older, low powered car. We were towing a caravan, and the car was jjuusstt coping with slight ups and downs. Then, when it got hot (we had started in the cool morning), we turned on the air-con.
Yup, aircon does make a difference. Now we could only tow it on the downhill, and acceleration was pitiful.

The load on the alternator does effect the strain on the engine.

And, if you want to prove it to yourself, grab a cheap DC motor. Spin it, see how easy it turns? Now solder a wire across the two contacts (shorting them). Now it is a lot harder to turn. The wire simulates a huge load, like what radios and air conditioning will place on a cars alternator.
trebuchet03 I'm just getting on the scene here, doing some research. I'm giving a lot of weight to your comments. You seem to know your stuff. It looks like you and another poster were speaking around each other. I think the other poster has it mixed up a bit, in that an alternator and typical electric generator/electric motor work a bit differently. Specifically where "Magnets" are concerned. Please correct me if I'm wrong.

If I'm correct, as are you, the increased spinning of the alternator will not increase output. It's not the input spinning that's the factor but the load placed on the alternator. The alternator will meet the load without an increase in the input rotation.

Again, please correct me if I'm wrong. Do know if you'll see this but if you do I'd appreciate your response.
they have some voltage regulators inside that keeps a constant voltage no more than 14v
JustinC49 months ago

Nope. This is false. I have an OBD Bluetooth connection to my tablet. This method sucks up fuel like a sponge. A nice slow acceleration is what is best, besides truckers (who have Standard Transmissions) do the same and they're all about conserving fuel. My car is an automatic.

Agreed. I use Torque on my tablet and slow and easy is the best way to accelerate. Ive tested it over and over while watching fuel flow, engine load, time, distance, etc. But us truckers start off slow because we have 13 gears to go through not to mention they weigh 80,000lbs. Plus most new trucks have an auto acceleration on take off. Meaning the engine idles up on its own as you raise the clutch. If you arent fully loaded you dont even have to touch the gas pedal until 3rd gear.

danwat12341 year ago

Keep in mind, if you have a torque converter automatic, trying to make the transmission go to lock-up or soft lockup as early as possibly is good for fuel economy. The more a torque converter slips, the more waste heat end ups up in the transmission. Also if you press too much on the gas, the engine computer may have the engine run rich, as in lower than 14.7:1 air to fuel ratio.

A scan gauge or torque smart phone app thing can help with this

pgan0021 year ago

In traffic (city driving) keep a large distance to the vehicle in front of you to reduce the probability of having to break. This is also safer, as you have more time to react.

On the highway, I would suspect tailgating increases fuel economy because it decreases drag. You have to watch in front of the vehicle(s) you are tailgating and anticipate obstacles that will cause the driver(s) in front to break.

pgan0021 year ago

To avoid stopping at a red light, try to arrive there just after it turns green again; if there is traffic stopped at the light, arrive just after it is leaving. This usually means breaking lightly, rather than coasting, as soon as the turns red. If you coast you might arrive too early and have to stop. But do not break too hard. Start breaking lightly and increase your breaking, always keeping your speed strictly above the speed required to coast to the light. Knowing the optimum speed comes with experience.

reddeth8 years ago
It takes a lot of power to get up to 40 MPH, even going from 30, this glide on/off idea is not only dangerous, but cannot stand to be truly effective, you're using a lot of an engines power to make it back to 40 MPH, this may be different for electric/hybrid cars running on the electric motors, which in turn use deceleration and braking to generate more power but on a traditional gas powered car this would not be a productive enough maneuver to outweigh the danger you present to other motorists by the constant accelerating/decelerating.
trebuchet03 (author)  reddeth8 years ago
...but cannot stand to be truly effective...

The pulse and glide method has been empirically tested by many people. Remember, while linear energy (momentum) is conserved - power is not. This is where the pulse and glide method shines. As for danger, possibly. I find myself much more alert and in every defensive driving course I have taken - evasive action is done by braking and steering.... Not gas and steer ;) Also take into consideration that you should be giving yourself plenty of space to begin with ;)

Here's Just one, well written example
I still find it questionable, but this isn't a forum for discussion, thank you for the link, thats all I'll say on the subject.
trebuchet03 (author)  reddeth8 years ago
I still find it questionable,

That exactly the attitude I want from people :) And I mean that with no sarcasm whatsoever :D Go out and test for yourself, see what data you end up with :D There are some better explanations out there which I can dig up if you'd like - but all I ask is that you keep an open mind :)

But, as a quite example from my numbers.... I might pulse for 7 seconds while getting 20 or so mpg -- and then I'll glide for at least double that getting ~180-200 mpg (that's engine on, clutch off). If I were cruising for that same 21 second period, I might be getting 31. That's not enough information to put everything together (I'll have to go out to my car and grab my notebook for that), but perhaps that glide number brings it into the realm of feasibility for you ;)
The correct answer is that for most vehicles pulse and glide results in worse fuel economy. It only helps with specific vehicles, most of which are hybrids.

The problem is the method was suggested as if it applies to any vehicle (by omission of vehicle parameters necessary to benefit from it) when for "most" people it is worse because most people don't own applicable vehicles.
I must have forgotten my 2003 5.4L V8 F150 was a hybrid... I can get about 25 mpg on the highway, quite an improvement.
M0HIZ2 years ago
Correction: air resistance/drag goes up as the velocity squared, not cubed.
Outlander8 years ago
No real pay off here. My old 87 Oldsmobile cutlass achieved 21-23mpg highway with a carbed 5.0L V8. This is one of the most non-aerodynamic cars ever made, but! A new V8 dodge charger only gets 17-18mpg. Something most likely a lot more "aerodynamic" than an old square 4000 pound muscle car, but yet it achieves even less fuel mileage. One the of the most aerodynamic cars, the smooth looking mid-late 90's camaros only achieved 24-28mpg. Aerodynamics has very little to do with MPG unless one is planning on driving 200 MPH. Sorry to be a negative Nancy, but it's true.
Aerodynamics don't matter until 200mph!? Try riding your bike behind a semi and then against the open air.
LMAO but true. that's why bike racers on Tour de France wear those helmets and not a block shaped one
trebuchet03 (author)  Outlander8 years ago
Once 4000 pounds of car is no longer accelerating (say you've stopped at your cruising speed of 70mph), it takes no additional force to move the mass of your car EXCEPT that of resistance forces coming from: 1) Rolling Resistance 2) Aero Resistance Ride a bike on a windy day and tell me that aerodynamics doesn't matter. You're comparing different cars, with different power trains and making a link to aerodynamics. That is what's known as a fallacy ;)
Not true again. an 87 olds cutlass vin 9, and some vin y's used the 4 speed overdrive 200-4R. Every single GM car has used the 200-4R and 700-R4(a less efficient but tougher trans.) since the late 80's up until the early 2000's The 4L60 and 80's are nothing more than an electronically controlled 700-R4. As for the engines, not much has changed, still 5.0L, 5.7L 90deg roller V-8. The fuel, electronics and induction has changed over the years, but still the same. Simply look at the EPA rated MPG figures for each. There is no major change, or difference. On some models there has been a change for the worse. As with the 4.6L ford. The fuel economy has dropped since going from the 5.0L going to the "modular" 4.6L. No real positive change. hope that makes some sense for you.
trebuchet03 (author)  Outlander8 years ago
So you're saying your 87 cutlass has the same shape as a charger and camero and the same exact power train (mind you, electronics is an integral part) - and then go on to say the changes that have been made (and some not so good). Honestly, I don't care about what changes have been made over the years - if they are not identical, you're practicing bad science. Again, when you want to make a link to aerodynamics - control everything, except aerodynamics. Here's a perfect example - the TV show myth busters did a bit on Tailgate up versus down. They took two identical vehicles (brand new, same mileage), then had one tailgate up, and one down with rules fro driving technique. Same power train, a best effort to control driving technique, two different aerodynamic configurations and a full tank of gas. 800 or so miles later, the truck with it's tailgate down ran out of gas - the other truck ran out of gas around 40 or so miles later. Later, it was empirically tested with a fuel consumption meter -- again, tailgate down consumed more fuel.
 OMG, if aerodynamics didn't make a difference then why is there such a term?
True, if you look at any race vehicle you will see any or all of the following: 1) a spoiler, this is a airfoil that uses the wind to keep contact to the road, why because the natural aerodynamics of a car suck and that mostly is from air going under the car which leads to the next item. 2) a splitter, this is a curved gap filling board of sorts, this is used to get the vehicle as close to the ground and diminish the gap, or reduce drag and improve aerodynamics. So anyone that says aerodynamics is fake or doesn't work..... well haha go on paying for gas as we pass you at the gas station..... haha
So, basically you're saying that if electronic engine control really makes milage better, or at least wasn't just an unnecessary complication, then a more aerodynamic car should not have lower rated milage, am I reading you right? Two things have changed: engine control and car shape. So assuming that the new engine control is better, it must be the car shape causing the lower milage. But since we know from experience that wind resistance does actually matter, we may have just proved that most electronic engine management is all smoke and mirrors. Another possibility is that you're quoting sports cars, which are generally tuned for downforce. Of course, downforce gives you more grip, but robs your straightaway speeds and fuel economy, which is especially obvious in stock car racing. I do know, though, that my dad's '93 Olds Cutlass gets embarrassingly close to a brand-new Milan's milage, with more than 120,000 hard miles on it's clock. There's something amiss there from a technology standpoint.
jimmytvf5 years ago
that's what i'm talking about, playing with throttle and RPM. Low rpm = low fuel --> FALSE Low rpm make the time lapse between injections increase, so we get less fuel in a second, that's true, but, if we have to step more the throttle to get the same rpm, the volume of fuel increase, and the car needs energy to move and spend more fuel. you have to play with what your engine needs and, at the same time, manage the efficiency of the fuel you send to the engine
best rpm shiftings on petrol: 2000 to 2500 RPM
best rpm shiftings on diesel: 1500 to 2000 RPM (lower rpm torque point)
trebuchet03 (author)  jimmytvf5 years ago
To your earlier comment - this is why instantaneous fuel economy data is important ;)

Yes, we care about long term average consumption - but you won't get good long term averages if you can't keep your instant consumption low (as you accurately said: "play with what your engine needs").
yes, i've just realize about that ;)
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