I wanted to write this while my impressions were still fresh because the one thing I felt that I never explicitly said during our special episode was…anger. It made me mad. I felt used. Faraday Future, from here on, FF, used me for a sucker and I had to sit there and take it. Why? Well, let’s talk about it.
Many times, when discussing hypermiling techniques, someone will ask about how to approach a hill, or what to do in rush-hour traffic, or when driving in bad weather can’t be avoided. The only sane answer is, “get over it.” Let’s face it: if you are going to scrutinize every single mile or every single minute, you will go insane. That is why hypermilers talk in terms of tank averages and lifetime averages.
This should be your smallest unit of measurement except for the rare exception. It is only over the course of an entire tank that you can take multiple factors into consideration: morning versus evening commutes, good weather versus storms, etc.
If you wish to maintain daily logs – and for various reasons, I have suggested just that – bundle them into the tank average and then throw them away. Daily logs are for analysis and review only. For example, another article suggests keeping daily logs for the sake of identifying the best daily commute. Once these logs have served their purpose, dispose of them.
The easiest way to calculate the tank average is to divide the miles driven by the amount of gasoline used to refill the tank. However, here are some factors to consider:
Of course, the granddaddy of all averages is the overall Lifetime Average. This reflects your entire driving experience with the car. Lifetime averages do not need to start when the car is brand new; it is the one-number record of you and the car working together as a team, regardless of how old the car was when you two first met.
As you can imagine, calculating the lifetime average requires that you know exactly how many miles you have driven and exactly how much gasoline you have consumed. Not just for one tank or one month or even just one year. In order to calculate an accurate lifetime average, you must have been recording accurate fuel data for the entire time you have been driving the car. Trust me: this can get tedious but it is what must be done to achieve the goal.
12-Month Rolling Average
As you drive your car year-over-year, you might become curious whether you are becoming a better hypermiler. Actually, it’s great to constantly want that feedback to spur improvement. The problem is that the Tank Averages can’t be compared one-to-one and after a while the Lifetime Average barely budges.
This is where the 12-Month Rolling Average comes in. Whereas the Lifetime Average will forever be influenced by those first few crappy tanks, the Rolling Average will eventually let them go to reflect how you’re doing now. Though you can’t throw them out completely because they are part of your historical record, they are no longer an accurate representation of your current driving ability.
Calculating the 12-Month Rolling Average requires that you go back one year (sounds pretty obvious, doesn’t it?). Where it can get complicated is that the number of tanks will vary. For example, if you average a refill every other week, you cannot simply take the last 26 tanks and assume that’s a year. There will be those long-distance road trips in which you consumed a full tank in only two days. So just be careful and make sure to do the math based on the dates: sometimes 28 tanks, sometimes 32.
If you only keep two averages, they should be the Tank Average and the Lifetime Average. These give you a real-time feel for your hypermiling abilities and an overall view of your entire driving experience. Adding the 12-Month Rolling Average provides an updated perspective, showing how you’ve done over the past year.
“That which is documented is measured.
That which is measured is improved.”
There are several attributes as to who originated that quote, whether it was ever actually spoken, or whether it’s a mash-up of multiple quotes. As important as is the origin, the impact it can have is equally so. Basically, it’s this: if you want to improve something, start documenting. However, documentation does not, in and of itself, result in improvement. That’s where the middle step comes in: the documentation must be measured and comparisons must be made. After all, sheets of detailed documentation would be meaningless if they were tucked into a binder and never reviewed.
What Do We Document?
The following is going to be a list of as many possible things as I can imagine. In no way am I saying that you must document it all or even that every item is important to you. It’s up to you, your priorities, and your gumption to decide how far you wish to take the whole thing.
Route Timing (with waypoints)
Sometimes, the speed of the drive is more important than the mileage. Or perhaps you’re interested in finding out exactly how much longer it takes to drive one route compared to another. Consider using a small notebook and a pencil to make note of when you pass certain intersections or other static waypoints.
Create a table on the sheet. Down the left, list all the waypoints. Along the top, list Mon, Tue, Wed, etc. or perhaps Day1, Day2, Day3. Whatever. The waypoints should be far enough to allow a measureable amount of time but close enough that the measurements aren’t a half-hour apart. For example, when I did this, my 50-minute commute had eight waypoints, mostly represented by stoplights, four-way stops, or important turns.
Some unexpected benefits to logging when you pass certain areas include knowing when the train comes, knowing the school bus routes, knowing when businesses let their employees out, etc. Sometimes it’s possible to identify something that had always been taken for granted but can be completely bypassed by adjusting your travel time.
The key to logging the travel is to be accurate to the time displayed on the clock in your car. From day to day, you might leave at approximately the same time but perhaps not exactly the same time. Don’t worry about that. Just record the time exactly as the clock shows it. After the trip, go back and figure out the time it took to travel each segment. Do not attempt to calculate the travel time until after the trip is complete. Driving is hard enough without performing math.
Don’t expect a good average for the segments until you’ve driven the same route for a full week. By that time, you will know very precisely exactly when you will be passing specific points in your drive based on when you started the drive.
Route Congestion versus Travel Time
If you have the liberty, consider driving your regular commute at different times to see how traffic patterns vary. We’re not talking about hours apart, here. But no doubt you’ve noticed that leaving home fifteen minutes later than usual results in completely different traffic characteristics.
Why would you do this? If you are going to be working on achieving good mileage, you might want to be surrounded by fewer cars. For example, it is harder to pulse and glide when you are creeping along in bumper-to-bumper congestion. On the other hand, you will have fewer opportunities to drive at the speed you want when the few cars on the road want to drive all-out as fast as possible.
The key is to find that time when there are enough cars on the road to keep everyone at a reasonable pace but not so many that it’s a parking lot. I’m not going to tell you that such a situation exists in your area, but it might and you might not know about it.
The good news is that some newer cars display the trip mileage on their own. You simply need to write it down at the end of the drive. If you have an older hybrid, however, you might need to reset the trip odometer to get the mileage for just that trip. If you have a non-hybrid, you might not be able to calculate the trip MPG at all. I say that because – unless you have another way – the only way to manually measure consumption over distance is to start with a full tank and then top off the tank when the drive is over. Since we’re talking about single-trip calculations, the amount of fuel consumed will be miniscule.
Documenting the Trip MPG is nice, but by itself, only presents a part of the story. For example, yesterday your trip MPG was much higher than today. Why? Without other variables, it might be impossible to know. Which is why you might want to also consider documenting. . .
Anyone who has driven a hybrid for more than a couple years knows that the ambient temperature really does have an impact on mileage. On the surface, it is easy to see that when the temperature is lower, the mileage is also lower. However, a little digging will reveal that the engine block cools down faster in the cold air and ran more to keep warm; the battery was cold in the morning and wasn’t running as efficient; or perhaps you were cold and ran the heater. Likewise, a hot battery pack is not a happy battery pack and you are more inclined to run the A/C when the temperature is above 90F.
And so it is that with the combination of trip MPG and temperature, the mystery of why today’s mileage is different from yesterday’s might be settled with an examination of the role played by ambient temperature.
Most hybrids and some newer conventional cars maintain an average MPG that the user can reset; many users reset it when they refill their gas tank. In this way, an average for the entire tank can be recorded. Another way to record the tank average is to divide the number of miles driven (per the odometer) by the amount of gasoline physically pumped into the tank. This can confirm the car’s calculations or prove it wrong. Some hybrid drivers have proven that even if the tank-to-tank calculations don’t match, they tend to even out over time. Which is to say, the car’s calculation and your manual calculation might differ for individual tanks but over multiple tanks, both methods return a very similar calculation.
Average Tank Temperature
This one is a little controversial. I didn’t think it would be, but clearly I was mistaken. When I recorded and posted my tank-to-tank averages, I would refer to weather.com for temperature readings. Here’s what I did: in a spreadsheet, enter all the high and low temperatures for each day during that particular tank; then average all the numbers. This is the value I entered as “average temperature for the tank.” Was I actually driving at the hottest or coldest points of the day, every day? No. What about the days I worked from home and didn’t actually drive; did I include those days in my calculations? Yes. Why? I simply didn’t care enough to be that precise. The end result was, as far as I was concerned, close enough.
How Do We Document?
This one is entirely up to you. File it under “try a lot of things and go with whichever one works best for you.
Personally, I record the tank averages. There is an added convenience to this: with every fill-up the gas station gives me a receipt. On that receipt is the exact amount of gasoline I pumped to which I add the car’s reported average MPG and the odometer’s recorded distance. The amount f gasoline simply adds into the “total amount of gasoline consumed”. The tank distance is primarily used to verify the overall odometer.
A friend keeps a small notepad and pencil in his glove box. He records all the pertinent information there. He never transfers the data and refers to the notepad when he wants to look up past tanks. Since I transfer my numbers into a spreadsheet, the gasoline receipt is temporary.
How Do We Use the Measurements?
Most people keep their documents because they simply want to know their own mileage. It surprises some people have quickly a problem can be detected simply by monitoring the mileage. For example, some people have been able to determine they get better mileage with one gas station versus another. Others have been able to identify a failing 12-volt battery through a drop in mileage. Of course, if a hybrid battery is starting to fail, overall mileage could be a forbearer.
My spreadsheet started simple but became more complicated in time. I started with:
With these four data points, I was able to create a historical trend graphic showing tanks over time compared to the average temperature for each tank. The “Tank Miles” was only because I wanted to know how many miles I could travel on a full tank of gas.
In time, I started getting curious about other calculations such as a rolling 12-month average and the Lifetime Average MPG. With the Lifetime MPG, I can use the sum of all Refill Gallons (Total Gallons) to compare my car to any other car driven the same total distance. By using their estimated MPG, it’s easy to show how much more they spend in total fuel costs.
Here is a screen capture showing one 12-month span from August 2010 to August 2011. This format shows the raw numbers and automatically generates the chart underneath. With the temperature shaded in the background, it is amazingly easy to see the direct impact temperature has on overall mileage.
Whatever your intentions, without proper documentation there cannot be proper measurement and nothing will improve. Think of it this way: if you want to tell someone you get good mileage or that you drive the quickest route, or that traffic is always bunched up this time of day, be prepared for them to say, “prove it.”
In this post, I will attempt to provide a simplistic overview of a hypermiling technique known as “Pulse and Glide” (P&G). Before we get started, you need to know that the application and technique for P&G is variable based on many factors such as the car, terrain, traffic, current speed limit, etc. For all those reasons, this will be an overview and not overly detailed. My concern is that if I provided any real details: 1) you would try to apply the details where they don’t fit, and 2) someone will argue the minutia of the details.
How Do You Pulse and Glide?
Many times, I compare hypermiling to riding a bicycle. This works because almost everyone knows how to ride a bike, which makes it a universal reference. Also, you most likely remember how tired you can become if you do not ride efficiently. Though neither you nor your car will get tired, you have to focus on the amount of effort being exerted; the goal is to travel farther with less effort.
The Pulse. Just like riding a bike, the intent of the pulse is to get up to speed. When accelerating from a dead stop, use a brisk acceleration: accelerate quickly but not stomp on the gas. Once you have reached a speed that is, perhaps, a little faster than the speed limit or average traffic speed, let up on the accelerator.
The Glide. Think about riding that bike. Once you have reached a decent speed, it requires only a minimal amount of effort to maintain it. In fact, depending on the situation, you might be able to coast for a long distance before needing to pedal again. In exactly the same way, the point of the glide is to “stop pedaling”.
The first and second generation Prius were exceptionally good at gliding because they had a “dead band”. This dead band is a spot in which there would be no power coming from the engine or batteries to drive the wheels and also no regeneration from the wheels to the batteries. A practiced driver could work the accelerator into that dead band and let the car roll.
Unfortunately, this type of “free wheeling” is nearly impossible in almost all modern hybrids. And so it is with modern hybrids that the glide is an attempt to reduce the energy flow to a point as low as possible.
Pulse Again. As you can imagine, after coasting for a while, you will start to slow down. Once you’ve slowed to a speed you are no longer comfortable with, pulse again. Unlike the dead-stop pulse, this time you want to use just enough acceleration to get back up to speed. Just like riding that bike, it’s not a sprint back up to speed but rather just enough.
And then you glide again. Then pulse, then glide, repeat.
Why Does it Work?
The concept is simple: the entire intent of P&G is to glide more than you pulse. The following image provides a sort-of representation starting from a dead stop, accelerating up slightly above the desired speed, gliding, pulsing, and then gliding again. As you can imagine, the farther you can glide the better. The black line in the following image might represent the average traffic flow, the speed limit, or simply the speed you want to average. Your situations will vary.
It works because gliding is essentially free. It’s the pulsing that costs you. Therefore, rather than paying to constantly maintain a steady speed, you allow your speed to vary. The trick comes in making sure the pulsing uses less effort than would otherwise be used maintaining a steady speed.
So many times, when it comes to achieving higher mileage, people focus on their car and how they drive. Most times, they just assume the commute is an unavoidable variable. A predefined route that some days has good traffic while other days has bad traffic. This article will explain why the route you take and how you drive it plays as much a role as all other variables. When it comes to improving, never consider anything to be predetermined. The goal is to scrutinize everything.
Find a Mileage Friendly Route
If you happen to live in a large city, there’s a very good chance there are multiple options when it comes to the daily commute. Personally, I have three choices that I will call “Fastest”, “Easiest”, and “Hypermiling”.
“Fastest”: I have the opportunity to hop on an interstate for about ¾ of my commute. Doing so would save about ten minutes and is an attractive option when time matters. The downside is that the interstate maintains a relatively constant 70 – 80 MPH except when it comes to a screeching halt for no particular reason before slamming back up to 70 MPH. In other words, exactly the opposite of hypermiling.
“Easiest”: There is a state highway that runs is literally a straight shot from town to town. Albeit, one with multiple stoplights. Like the interstate, traffic is either racing along (though closer to 50 MPH), stopping for the red light, or accelerating Grand Prix style at the green light. It’s a multi-lane stop-and-go early-morning ball of stress. In no way do I look forward to starting or ending my day on this drive.
“Hypermiling”: This drive is 5 miles and 9 minutes (on average) longer than the “Easiest” route. This drive has longer stretches without stoplights and some stoplights are timed. It passes two schools and one nature preserve. The highest speed limit sign is 45 MPH. It is on this route that I see joggers, walkers, and the occasional wildlife. On nice days, I drive this route with my windows down enjoying the sights and sounds. All the while, the speed is conducive to attentive hypermiling and plays into the capabilities of my car.
By selecting a different route, I can not only achieve better mileage, I can choose how my day starts and ends. If you find that you arrive at work already stressed and you return home mentally ragged, do yourself a favor and seek out a more casual and hypermile-friendly route.
Memorize Your Route
Here is an analogy parents can appreciate. Let’s say your son goes to the first day of school and is presented with a difficult, lengthy exam. How would you expect him to score on that exam? Probably not very good. On the second day, he is presented with the exact same exam. Should he do better than the day before? Perhaps. Let’s pretend your son is presented with the exact same exam every day for the entire 180-day school year. You would expect him to be acing that exam with absolutely no effort, wouldn’t you?
Now what about people working an average 250 days per year? Most of them drive the exact same route every day, to AND from work. Even after all this repetition, it has been my experience that people drive their daily commutes as though it’s their very first time. Every time.
You are a human (I hope). You are preprogrammed to identify and memorize patterns. It’s what we do.
If you drive a hybrid, consider basing battery usage on drive segments. Pick up some charge during the fast segments in order to run farther on battery during the slow segments. Or vice versa: consider going deep into the battery pack if you know an upcoming faster segment will allow you to recharge. Recharging will impact the instantaneous mileage. Ignore that; it’s the average that matters.
It’s all about driving the same route every day, figuring out what works best, and repeating it.
If you have the opportunity, drive a route that returns the highest mileage. If it turns out to also be least stressful, then it’s a double-win. The only way to know which route is the most fuel-efficient is to document each pass in order to develop an average and recognize patterns. Once the best route is identified, memorize how to handle each segment with the intent of getting better with each day.
First of all, I want to make it clear that this is not an article about drafting. To prove that point, let me explain what drafting is and why it’s dangerous, illegal in some places, and a really, truly, and seriously bad idea.
In auto racing, drafting is also referred to as “slipstreaming” because the goal is to ride in the slipstream of the car in front. In order to do this, the trailing car must be close enough to the leading car to stop the air from collapsing around its back. By doing this, the airflow moves around both cars as though they were one single vehicle. Since much of the effort of propelling any object goes into wind resistance, the trailing car is able to travel much more efficiently. This is shown in the following image, stolen from efluids.com.
Drafting is most beneficial at high speeds where wind resistance is great. This is why racecars draft and some people draft behind semi trailers on interstates. Drafting is rude because the trailing car is much too close to the leading car. It is also extremely dangerous because driving can be unpredictable and drafting leaves virtually no room for sudden movements or braking. To reiterate: don’t do it.
So What’s the Difference
Driving behind a large vehicle at a safe distance is similar to drafting only in that the vehicle in front takes the brunt of the air resistance. Unlike drafting, the trailing vehicle is following at a safe distance. The benefit to the trailing vehicle is that the lead vehicle has disturbed the air in such a way that it does not represent as much resistance to the trailing vehicle.
Notice in the illustration above that the air flow lines are drawn parallel to each other in what’s called “Laminar Flow”. Air is illustrated as strata – or sheets – of air that don’t interact with each other. This does a great job of showing that air is moving around the car, but this is not how air really flows. The goal of most automobile manufacturers is to perturb the air as little possible in order to make their car more efficient.
However, there are many not-so-efficient vehicles on the road such as delivery vehicles, semi tractor-trailers, etc. These vehicles have large flat backs and leave huge eddies of air as they travel. Anyone who has ever been standing on the side of the road when a semi tractor-trailer rolled by understand just how strong their wind currents can be. Depending on the aerodynamics of the truck and their speed, their wake can extend hundreds of feet. This is illustrated in the following image.
This image is probably the best to illustrate the difference between following at a safe distance and versus drafting. Someone drafting would want to be in front of the red, disturbed air, between the truck and the first marker line. Notice how the dark blue actually curls up and towards the back of the truck? This will literally pull the trailing vehicle towards the truck’s bumper. Following at a safe distance has the trailing car behind the disturbed air, in the light blue area, almost two truck-lengths away. Even at that distance, there is benefit thanks to the disrupted air.
The Other Reason to Follow Other Vehicles
Deserved or not, hybrid drivers have a stereotype of being slow drivers. Sadly, I have seen some cases in which this reputation is strongly earned. Having said that, there are times when I am on a multilane road and I just don’t feel like driving like a bat out of Hell, acting as though commuting is a competitive sport with a trophy handed out if you get to work faster. Perhaps I only want to drive a few MPH above the speed limit and have no concern with keeping up with the general flow of traffic.
Sometimes, I come upon a delivery vehicle or lawn care truck that is driving close to the speed I prefer. In this situation, I will maintain a safe following distance and stay there. There is a very good chance – like many of my phobias – that it’s all in my head, but I like to think that rather than me being the slow car now it looks as though I’m the poor car stuck behind the slow vehicle. But I don’t care because in the end I get to drive at my desired speed. This might sound like a stretch, but I was a little relieved to see a post on an online forum in which someone asked if they were the only ones to apply this technique. Multiple people admitting to it.
At a slower speed, any benefit from perturbed air is minimal if there is any at all. The primary point in following a large slow vehicle is the benefit of not feeling as though you are being pressured to driver faster than you would prefer.
Drafting is a really stupid idea and extremely dangerous. Following large vehicles at a safe distance can reap aerodynamic benefits without risking your life. Sometimes following slower vehicles gives you the opportunity to get out of the roadway racetrack and drive at a more comfortable speed.