Increasing Fuel Efficiency
The primary difference between a regular car, and a hybrid vehicle, is the way the engine works. In a normal vehicle with an internal combustion engine, when you step on the accelerator, you are using gasoline. The processes it goes through to enable your car to accelerate are varied and complex, but not as nearly as complex as a hybrid engine. As you can see from the diagram below, a hybrid vehicle is powered by more than gasoline.
A hybrid vehicle receives power from a battery, which is then transferred to an electric motor. The power from the battery is then channeled through the electric motor and is combined with the power generated from the gasoline engine to accelerate your car forward. One common mistake people make when thinking about a hybrid car, is that a hybrid car runs solely on electrical power from the vehicle’s battery. This couldn’t be farther from the truth. Hybrid vehicles use electrical power as well as its gasoline engine to get the car from Point A to Point B. However, the true efficiency of a hybrid vehicle can be seen when the car isn’t even moving at all.
When idling, a normal car continues to consume gas. It is important to remember that just because the car isn’t moving, and your foot isn’t on the accelerator, doesn’t mean that your engine isn’t consuming costly fuel. In fact, it has been found that when idling for more than ten seconds, it is more efficient to completely turn your car off. The fact is that your car consumes less gas when turning the ignition, than it does in ten seconds of idling! For you skeptics out there, you may say that the constant wear and tear off turning your car on and off at busy intersections is not worth the risk… Those who have practiced the aforementioned technique have said that the amount of gas they saved (in some cases upwards of a gallon per tank) led to sufficient savings that even if they had to replace the starter, it would still work out that they would end up saving money over keeping their car idling.
So, with the concept of a hybrid car somewhat etched into your mind, I offer you my personal advice on how to save gas both in the city, and on the highway.
There are many ways you can increase your fuel efficiency, but I have yet to find any that make as big of an impact on your vehicle’s fuel efficiency than coasting (excluding the obvious concept of driving the speed limit). However, it is important that you do not believe that coasting is all it takes. No, in fact, coasting is only half of the solution. As I mentioned before, hybrid vehicles save gas by shutting off the gasoline engines supply of fuel while idling, or when first accelerating. You can duplicate this process in your own non-hybrid vehicle.
When you put your car into Neutral, you are effectively regulating and severely cutting the amount of gas sent to your engine. So much that you can see tremendous gains in fuel efficiency just by shifting into neutral at red lights and while idling. But why stop there? For those of you who travel on stretches of road (whether its city or highway) in which you encounter dramatic downhills, you can see exponential gains in your car’s gas mileage by not only coasting down the longer stretches of road, but by also shifting into neutral while coasting.
MPG Weekly Challenge
I would like to take a minute to turn your attention to an excellent device that I bought for my car. It’s called the Scan Gauge II, and what it does, is it allows you to monitor the amount of gas you are using. It keeps track of your fuel efficiency in real-time, as well as daily efficiency, and the mileage per tank fill up. I would highly suggest purchasing this small and inconspicuous device for your car, it enables you to keep track of exactly how much gas you’re using, and in turn, helps you find ways of using less gas, whether its by easing up on the accelerator on a certain part of the road, or by finding out that a different route gives you better fuel efficiency.
I recently installed my Scan Gauge II into my ’02 Ford Mustang. My Mustang is a six-cylinder with a 3.8L engine. The EPA has the fuel economy rating of a 2002 Mustang 3.8L V6 at 19 MPG City / 24 MPG Highway (with a combined overall rating of 20 MPG). So I decided to put my theory to the test. I decided that I would spend the first week driving approximately 60-75mph on the highway (as is more than normal for many commuters) and not coast at all. I wanted to see if the momentum I gained from the continued downhill acceleration would net me a higher gain in fuel economy than if I merely coasted in neutral. For the second week, I would drive no faster than 60mph (unless by coasting I surpassed it), and when coasting, I would shift my car into neutral.
After one week of driving in excess of the speed limit (I do not condone this type of driving, it is merely part of the experiment) I took a look at the Scan Gauge II and jotted down my the combined fuel economy for that week… A jaw-dropping 17.9 MPG… Low even for a Mustang!
So I had high hopes leading into the second week. I spent the next seven days following the same route everyday to and from school and work, while taking advantages of the long downhills to coast and shift my car into neutral. At the end of the week, I logged the data from my trusty Scan Gauge and found out that my new driving technique had produced a fuel economy of 27.1 MPG (35% over the EPA’s fuel rating for an ’02 Mustang)!
I made note of what I did differently in each case. For the first week I followed these driving patterns:
– Routinely drove 60-75mph on the highway and 5-10mph over the speed limit in the city.
– Quick acceleration from red lights and Stop signs.
– I kept my car in Drive while idling, and kept coasting to a bare minimum.
– I drove the most efficient route to and from work and school.
– I did not take advantage of drafting large trucks or big rigs.
– I did not try to time red lights (Pulse and Glide Technique… explained later)
During the second week, I did the exact opposite of what I had done in the first week of data gathering:
– I consistently drove 50-60mph on the highway and never exceeded the posted speed limit in the city.
– I moderated my acceleration from red lights and stop signs.
– I switched my car into neutral while idling and coasting.
– I drove the most efficient route to and from work and school.
– I occassionally took advantage of drafting larger trucks and big rigs.
– I took full advantage of timing red lights. (YouTube Video Explanation)
So as you can see, with my particular car, and my specific situation, I observed a 51.3% increase in fuel efficiency just by driving in a safer manner, and by regularly coasting, and employing the same principles that a hybrid vehicle uses. While I cannot guarantee that you will see the same results, I can guarantee that by adopting the aforementioned techniques you will be able to see a gain in your fuel economy. Lets not forget that with gas prices at or above $4.00 per gallon, saving even the smallest amount of fuel in each tank can really add up over the course of a year. (The route that I drove during the two week experiment was made up of approximately 40% city driving, and 60% city driving).
Drafting Vehicles
One very hot topic today amongst drivers seems to be about the gains recognized by drafting. Drafting is a practice used throughout our world, where an object breaks the wind current, essentially cutting a whole in the air, allowing the object following it to be dragged along, unaffected by the drag induced by the air or wind. This can be seen in NASCAR, on the highway with fleets of trucks, and in nature with birds flying in V-formations. It is undeniable that drafting enables you to save a tremendous amount of gas.
To make this a more concrete concept, I took the time to apply physics into our argument. Using the drag, or resistance equation, I calculated the amount of drag my vehicle (an ’02 Mustang) encounters while driving at certain speeds. Please note that the following figures are tallied without wind speed in mind, they have been calculated without factoring in windy days.
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Drag Based on Velocity |
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MPH |
Percent Increase |
Resistance |
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100 |
1112% |
5,725.5668568 N |
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90 |
900% |
4,637.709154008 N |
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80 |
711% |
3,664.362788352 N |
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70 |
544% |
2,805.527759832 N |
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65 |
469% |
2,418.2194918 N |
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55 |
336% |
1,731.279557728 N |
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40 |
164% |
848.85257088 N |
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30 |
0 |
515.301017112 N |
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Percent Increase based from 30MPH to x MPH |
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NOTE- Resistance is measured in Newtons (the standard measurement of Force). Percent increase is based on the resistance encountered at 30mph, compared to whatever velocity is being compared. (While driving at 100mph, the resistance your vehicle encounters is approximately 1112% more than when you are driving at 30mph).
If you are still having difficulty understanding what drafting does, I suggest you take a look at this video from MythBusters. It involves a person on a bike drafting behind a big rig at 20mph, and although its not a car, it really shows you the difference in resistance and force required to move a vehicle while drafting, compared to when you are not drafting.
As you can see, the amount of resistance that your vehicle encounters from 40mph to 55mph and so on is astronomical. Through the application of physics we can clearly see the effect that drag has on our fuel economy. So, what if there was a way to minimize your car’s drag?
Drafting is a powerful weapon in our arsenal to combat rising gas prices and low fuel economy. However, it does not come without its risks. Drafting is both dangerous to you, and the vehicle you’re drafting. Let it be clear that I am not condoning drafting, I am merely stating the obvious from a scientific perspective… Drafting saves gas… Lots and lots of gas! But again, you have to wonder if putting yourself and your fellow driver at risk for an accident is worth the savings at the pump. Again, I in no way condone drafting, especially at dangerously close distances.
For more information concerning drafting, I urge you to take a look at the following links:
Mythbusters: Drafting a Big Rig
OmniNerd: Factors Affecting Fuel Efficiency
The “Pulse and Glide” Technique
I briefly spoke about the “Pulse and Glide” technique in the first section of this page. However, I would now like to focus primarily on applying this technique on the highway. This method is highly efficient, however, not always practical… Especially if you own a car with a manual transmission.
I will explain this technique assuming that you have an automatic transmission like myself. The Pulse and Glide technique has been developed and perfected by owners of many hybrid cars. We read about owners of the Toyota Prius getting 100+ MPG, and the hypermilers in Japan getting over 100 MPG as well. How on earth are they able to accomplish this? Its actually quite simple and only takes about a week to get used to.
The idea behind the Pulse and Glide technique is that like a hybrid car, once you achieve a certain speed, you can use your cars momentum to coast for stretches of the road. What I find most interesting about this technique is that it seems as though its a hypermiling contradiction. Pulse and Glide consists of two stages… Yes, you guessed it, the “Pulse” and the “Glide.”
In order to fully explain this, I will give you a scenario to envision. You are driving on the highway. The stretch of highway you are on is mostly flat, with several downhills and minimal inclines. The speed limit is 65mph and the closest car to you in your lane is approximately 200 feet away. You are driving at a conservative and safe velocity of approximately 55mph because you know that your car performs particularly well at that velocity. Now is the time to begin the Pulse. Steadily accelerate from 55mph up to 70mph. Once you have achieved 70mph (and you are on level, or a down hill stretch of the highway) it is time to begin the “Glide.” The Glide is exactly what you are probably guessing it to be. Just as a bird flaps its wings continuously and then uses the air and its momentum to glide effortlessly over our heads, the same goes for your car. When a bird glides, it uses no energy, it makes the air around it do all the work. The same principle works with your vehicle. When you begin the Gliding stage, make sure that you are on a level or down hill part of the highway and begin to coast, once you are sure that you have enough momentum to carry you for more than a quarter of a mile without dipping below 45mph it is time to initiate the final phase of the technique, of which I explained in the opening section. It’s time to cut your engine’s supply of gasoline. Shift from Drive to Neutral and glide. By accelerating to 70mph you build up enough momentum to power your vehicle’s glide.
Some of you may be scratching your head thinking… Wait, if you accelerate up to 70mph, you must be using a lot more gas than if you maintained a steady velocity at around 55mph. You are exactly correct! But before you congratulate yourself on putting a hole in my argument, think about this. When you are coasting in Neutral you car is getting an infinite about of MPG. In comparison, a car that gets 20 MPG while driving at a steady clip of 50-55mph on level road (i.e. a Jeep or comparable SUV) will get 999999 MPG while gliding with the same amount of acceleration while in neutral.
Still wary of what I’ve said? Something doesn’t make sense? Well I don’t blame you, with all the hype about hypermiling going on out there, it is important that you get all the facts before you can fully believe anything you read. So here are several sites that I’ve found that I believe are exceptionally helpful when it comes to explaining the Pulse and Glide technique:
Fuel Economy: Increasing Fuel Efficiency 