How Do You Hypermile?
In just the last week, we’ve seen three separate fuel economy records fall and go permanently to rest. Probably the biggest and most important, the record for non-hybrid fuel consumption on a long-distance trip. After trekking across 48 states and 8,233 miles, the driver of a certain bone stock 2015 VW Golf diesel managed a truly stunning 81.7 mpg — in a car rated for 32 city and 44 highway mpg. And who, might you ask, managed this incredible feat of skill and determination? Why, that would be Wayne Gerdes — the very man who coined the term "hypermiling" so many years ago.
The idea of driving a car for maximum fuel economy isn’t entirely new, but it did catapult into notoriety some years back with the birth of hypermiling. As our newest extreme motorsport, hypermiling quickly (and quietly) found a home among engineers, scientists, and other people who enjoy talking about things like adiabetic efficiency and the First Law of Thermodynamics.
That might not sound like the most exciting company in the world — but there was a lot of science, a lot of technical stuff and a lot of trial and error in the beginning. All very science-y. But now, after many years and many records fallen, hypermiling’s anorak forefathers have finally cracked the code of how to regularly double the average car’s gas mileage with driving technique alone. In truth, the specifics are all still very technical, and techniques will still vary greatly from vehicle to vehicle, and road to road. But here’s a basic primer to get you started on doubling your fuel economy with nothing more than patience, brains and precision driving.
Continue reading for the full story.
Preparation and Equipment
While hypermiling doesn’t necessarily require any special equipment, a little bit of preparation can go a long way. First, check your tire pressure. Tire rolling resistance is a huge factor in fuel economy, especially at highway speeds. The softer and lower-inflated your tires, the more they’ll drag on the road and cost you fuel. You want your tires as hard and round as possible. To that end, check that they’re inflated to at least the manufacturer spec. Most hypermilers will add 5 psi or so over the manufacturer recommendation, which is safe in most cases. Don’t take that as gospel though, especially if you have a heavy vehicle; check with a qualified mechanic or dealer if you’re not sure.
Take all the weight out of the vehicle that you can. Weight costs money, especially in stop-and-go traffic. Extra mass won’t hurt you much on the highway, where aerodynamics are the primary factor — but extra pounds will suck up fuel on acceleration at low speed. Many hypermilers never carry more than a half-tank of fuel, specifically to reduce weight. Sounds nitpicky, but gas weighs about 8 pounds a gallon; if you have a 15-gallon fuel tank, running half empty will cut about 60 pounds off the car. That’s almost 2 percent the weight of the average car, and you’ll see that weight reduction returned in fuel economy around town.
The DIY Initial D G-Meter
The legendary Japanese anime Initial D centers around a teenage boy named Takumi, who races his AE86 up and down mountain roads every morning delivering tofu for his uncle. In order to teach his nephew car control (and to avoid damaging the tofu), Takumi’s uncle places an almost-full cup of water in his cupholder before each delivery. The goal: To get all the way down and back up the twisty mountain road without spilling a drop. Basically, it’s a poor-man’s accelerometer
To make your own, just draw a line around a clear, plastic cup with a Sharpie marker, about an inch down from the rim. Set it in your cupholder, and fill it with water to about a quarter-inch below the line. Your goal is the same as Takumi’s: to not let the water slosh above the line under any conditions — especially acceleration, but also while cornering and while slowing down. The idea here is to keep you from wasting your car’s precious energy with excess acceleration, hard braking, or by turning the car’s forward momentum into useless sideways (lateral) G forces while cornering.
The Initial D G-Meter isn’t a necessity, exactly. But it will help you train your brain while first starting out, it’s fun, and it’ll make you feel like an awesome anime character.
Trip Planning — Shortest Route or Fastest?
Probably the single most important part of hypermiling starts with planning your trip. And obviously, it’s always a good idea to organize your stops with the minimum distance between them — or is it?
Hypermiling is all about not expending energy you don’t have to, and conserving the energy you’ve already used. That means, above all else: Avoid traffic, and maintain forward momentum at all costs. So, the shortest route isn’t always the best one if it involves a lot of turns and traffic. Most times, you’ll find your best fuel economy on the fastest route. That’s where you’re spending the least time stopped, and the most time preserving your momentum.
If you’ve got a navigation system: Set it to take you on the fastest route with the least traffic, not necessarily the shortest route. You can always drive a bit slower on a fast road in order to save fuel; but you can’t preserve momentum when you have to stop every 15 seconds for a red light.
Idling and Timing
Idling is generally something you want to avoid at all costs; most of that comes down to trip planning, but a lot of it comes down to timing traffic lights and traffic
It is technically best to shut your engine off if you think you're going to idle for more than 5 or 10 seconds.
Wherever you’ve got the option, stay as far back from the car ahead of you as practicality will allow. That way, if they hit their brakes you may be able to coast down to a lower speed without having to hit your brakes, or stop and idle behind them if they stop or turn. Remember, maintain forward momentum, and avoid coming to a complete stop whenever possible.
That goes for traffic lights and traffic, too. Look as far down the road as you can; if you see a stop light, stop sign or traffic ahead, let off the gas and start coasting. Don’t accelerate toward stationary objects — that’s just an epic fail in every way imaginable. Start slowing down the second you think or know you’re going to have to. You won’t waste fuel maintaining speed for a known stop, and you might be able to slow down enough to time a traffic light or stopped traffic. One more time: avoid coming to complete stops whenever possible.
If you do have to idle: With modern cars, it’s almost always technically best to shut your car down immediately. That old saw about how it takes 30 seconds worth of fuel to start an engine doesn’t apply to new cars. Realistically, a newer car in decent shape might waste 5 seconds worth of fuel while starting up. So it is technically best to shut your engine off if you think you’re going to idle for more than 5 or 10 seconds. That’s the ideal, and it’s what cars with start/stop technology do.
In the real world, those cars use super-powerful starting motors and batteries designed for the load. In a normal car, you’d probably end up frying the starter, battery or ignition key switch pretty quickly if you actually shut the thing down and restarted at every stop light.
So save the start/stop technique if you know you’re going to be sitting for a while. Or better yet, just try timing your driving so you never have to stop at all.
There’s an old saying in hypermiling: "Drive like you don’t have brakes." On a lot of levels, driving your car like the brakes are literally broken will help you to develop a lot of good habits in terms of following distance and cornering speeds. But more importantly, it’ll force you to simply coast while decelerating. That preserves more of your car’s forward momentum, instead of just burning it off in the brakes.
On a lot of levels, driving your car like the brakes are literally broken will help you to develop a lot of good habits in terms of following distance and cornering speeds.
The "Driving Without Brakes" technique is actually one of the oldest and most reliable in hypermiling; it was one of the first developed, and still delivers results more consistently than almost any other technique. Enough cannot be said about the evils of brakes and braking — even for hybrid and electric cars with regen capacity.
On a really good day, a very good electric regen system might recapture 80 percent of the energy it expended accelerating. Most electrics run about 60 percent, and hybrids will typically recapture 30 to 40 percent. That’s certainly a lot better than none, but it’s still wasting energy. You’re a lot better off practicing Driving Without Brakes than relying on regen systems to make up for it.
It’s also worth mentioning here that a lot of modern electric cars have auto-regen features; meaning, the car automatically starts applying a certain amount of brake regen as soon as you lift your foot off the accelerator. That can be handy in stop and go traffic, if you can get used to it. But really, all these auto-braking systems do is reduce your coasting time and engage the regen system. Which, again, wastes energy. So, if your car has this feature, turn it off and continue to drive like your brake pedal doesn’t exist.
Just follow that principle as often as possible, and your sense of self-preservation will usually lead you to the right hypermiling decisions.
This is one place where your handy Initial D G-Meter can make a big difference.
As anticlimactic as it might sound, accelerating like an old lady usually is the surest method with today’s cars. But what does that mean, in terms of practice? As a driver, you want to think in terms of "rate of acceleration." That is, accelerating very gently from a standstill, and focusing on maintaining that rate of acceleration until you get up to speed.
As anticlimactic as it might sound, accelerating like an old lady usually is the surest method with today’s cars.
The old adage is "Drive like there’s an egg under the gas pedal." But think of it as "rolling into" the throttle. Meaning, you start the car moving at a certain rate of acceleration (say 1 mph / per second), and then progressively add throttle as necessary to overcome wind and rolling resistance. No matter how fast you go, you always want to keep adding just enough throttle to maintain your 1 mph/per second of acceleration, until you get to the target speed. Don’t worry about the throttle position — just focus on maintaining your rate of acceleration. One mph / per second is a good baseline rate for most cars, though you can adjust that up or down as need be. But whatever rate you initially pick, stick with it until you get to your target speed.
If you don’t want to look at your speedometer and count mph, your Initial D cup can do the same thing. As you accelerate, acceleration force will push the water up the back side of the cup. It might slosh a little, depending on how firm your car shifts. But you want to focus on keeping the top of the water at exactly the same point on the cup relative to your line. Right below the line should be about right if you filled the water to a quarter-inch under it. Just maintain your rate of acceleration, and keep the water level consistent.
So don’t worry about your throttle position at all. Focus all of your attention on progressively rolling into the throttle, adding only as much as you need to to maintain the same rate of acceleration up to your target speed.
This one’s easy: Going fast costs money. Plain and simple. Over a certain speed, aerodynamics start pushing back against your car, the energy required to overcome wind resistance goes up with the square of speed. That means if you were to double your speed from 50 to 100 mph, you’d need four times as much power. Double that again to 200 mph, and you’d need four times as much as you did at 100 mph. So, even though 200 is only four times as much as 50, you need 16 times as much power to go that fast. Now you know why it only takes 150 horsepower to hit 100 mph, but 600 horsepower to hit 200 mph.
Over a certain speed, aerodynamics start pushing back against your car, the energy required to overcome wind resistance goes up with the square of speed.
That power requirement translates directly to fuel use. So, you might get 80 miles to the gallon at 30 mph; but double your speed to 60, and fuel economy drops like a rock to 20 mpg. Isn’t aerodynamics fun?
For smaller cars, aerodynamics usually come into play between 20 and 30 mph. Big trucks and SUVs, it could be 10 to 20 mph. Anything over those speeds, and you start exponentially giving up fuel economy to air resistance.
General best practice is to go as slow as your vehicle can go in top gear. If your vehicle shifts into top gear at 50 mph with your foot light on the throttle, that’s probably your ideal cruising speed. Any slower and you’d be in a lower gear wasting fuel. Any faster, and you risk angering the gods of aerodynamics.
So, while cruising: Go as slow as you can in top gear. Anything else is a compromise.
This has been the subject of some debate for a long time — but the matter has been more or less settled in recent years. Thanks not least to Wayne Gerdes himself. Common wisdom held for a long time that the most efficient way through a corner was the "racing line" — the path you’d follow across the apex of a turn while racing, as illustrated in this picture. It is usually the shortest path you can take while maintaining forward momentum.
Theory and experience have shown that the actual most efficient way around a curve is to follow it as wide and to the outside as possible.
However, theory and experience have shown that the actual most efficient way around a curve is to follow it as wide and to the outside as possible. That seems a bit backward to what you’d think — that following the shortest path around a turn would be the most efficient. But no, following the longest possible path will maintain more of your forward momentum, and keep you from turning it into useless lateral G forces. Hard cornering forces are always fun; but they’re also incredibly wasteful.
Remember the old 1980s Batman movies with Michael Keaton? You might recall his Corvette-style Batmobile was equipped with a side-shooting grappling hook that could snag telephone poles, and allow the Batmobile to round corners at insane speeds. The grappling hook and chain transferred the Batmobile’s forward energy in one direction very efficiently into another direction. So, after swinging around wide on that chain, Michael Keaton could exit a 90-degree corner almost as fast as he went in.
That’s how you want to think while cornering. Swing as wide as possible, and think of your car shooting out a Batmobile grappling hook to the middle of the turn. Follow the radius of the turn as wide as possible. If you have room to swing out even wider on the exit, then so much the better. Do it if it’s safe and you can manage.
As far as speed entering a corner goes — this again is where your Initial D meter could prove very, very helpful. Ideally, you want to be going so slow through a turn that (while following the outside of the curve) you don’t generate any sideways cornering force at all. But that just isn’t realistic, unless you go everywhere at 5 mph. You still want to minimize those lateral G forces though, because every bit is wasted energy. This is going to take a lot of practice, and no small amount of skill on your part.
Long before entering a turn, let off the throttle and coast. (Remember, you don’t have brakes.) You want to plan to be going slow enough when you enter the turn that your water cup meter doesn’t hit the line. Minimal G forces, always. How fast that is really depends on the radius of the turn and the width of the road — the tighter the turn and the narrower the road, the slower you’ll need to go to keep G forces down. Longer curves and wider roads will allow you to go faster hugging the outside of the turn while keeping G’s down to acceptable levels.
Again, this isn’t something you really need the Initial D meter for — even though a lot of serious hypermilers use electronic G meters for exactly this reason. You can use your own discretion, and try to keep side loads as low as possible. But a little visual aid will go a long way toward keeping you from wasting your precious fuel on pushing sideways.
So, there it is — your start on beating The Man by driving right to double your fuel economy. Granted, nobody’s claiming these little tricks alone will usher you to that kind of improvement; not everybody’s going to break world records right off the bat, and results will vary by vehicle and driving conditions. However, it certainly isn’t impossible you could double your mileage using only what you’ve learned so far — especially if you were doing everything wrong before. No shame in that, though. It’s not like they teach this stuff in driver training courses. Yet.
Still, you’re well-armed to get started. Let us know in the comments section how badly you’ve crushed your personal best mpg records, and keep an eye out for future articles on advanced techniques to hone your hypermiling skills even further.