Two of the most commonly asked questions about the Honda Insight are:

"What fuel efficiency should I actually expect?"
"How can I achieve the best efficiency possible?"

As you'll see in this section, these two questions are closely tied together.

"Your mileage may vary"

Real world mileage varies according to the sort of driving you do (fast freeway driving, slower country roads, suburban areas, congested city centers, etc.), and also according to how much attention you pay to getting good mileage.

Because mileage will vary a certain amount, you should view the 61 mpg city / 70 mpg (3.9 / 3.4 L/100km) highway figures only as estimates. In some driving situations actual mileage will be lower, while in other situations you can see figures quite a bit better than this.

For examples of real-world mileage figures, see the lifetime fuel efficiency reports and trip fuel efficiency reports pages.

Comparing with other cars

The bottom line is that in any given situation the Honda Insight delivers twice to three times the fuel efficiency of the typical car on the road. While actual mileage may be better or worse than the 61/70 estimates, because the estimates are generated using the same test procedures on all cars, they are indeed useful for comparing one vehicle to another.

Doing the right or wrong things can make a real difference

The 61/70 mileage figures also serve as a useful yardstick to see how well you are doing. As you'll see in the tips & techniques listed below, there are a lot of things that you can do which have a real effect on the fuel efficiency you see. Some are simple things that require little or no sacrifice on your part, while others require real effort or skill.

In the end, you need to decide how much you want to do in the quest for better efficiency. While some owners strive for the holy grail of a 70 mpg or higher lifetime average, others are content with a 55, 60 or 65 mpg lifetime average.

Keep in mind that even without you doing anything special on your part, the Insight will deliver amazing efficiency. Many of these tips are for those who want to do even better.

Share your tips & techniques

The tips and techniques presented here come from owner's experiences with their Insights. Please email me if you have other tips or techniques you like to use, and which of these techniques work best for you.

TIP: Check Your Tire Pressure

Effort involved / impact on driver: Low

The Insight's low rolling resistance tires are an important contributor to the Insight's overall efficiency. As explained in the low rolling resistance tire question, high tire pressure is an important part of the low-rolling-resistance equation.

Underinflated tires can really hurt the Insight's fuel efficiency. Unfortunately, many Insight owners have found that their dealers delivered the car with underinflated tires! Often the dealers have been setting the the tire pressures set to the typical Honda specs of 32 psi all around, rather than the Insight specs of 38 psi front, 35 psi rear. If you haven't yet checked the tire pressure set by the dealer, do it now!

Also, keep in mind that tires will tend to loose some pressure as time goes by, and so it is worth continuing to keep an eye on the tire pressure. If you don't have one, invest a few dollars in a good quality tire gauge. Dial-type gauges are typically more accurate than the pencil type gauges.

Note that tire pressure figures are given for cold tires. If you check your tire pressures after having recently driven the car, you'll get an inaccurately high reading.

TIP: Don't Limit Yourself to Honda's Specified Pressure

Effort involved / impact on driver: Low - Medium (depending on pressure)

I've stressed the importance of ensuring that your tires are inflated to at least the Honda-specified pressures of 38 psi front, 35 psi rear.

I say "at least", because some Insight owners are taking this a step further, and inflating the tires to even higher pressure. Some of these owners stay on the conservative side, at 40 psi on the front and 37 or 38 psi on the rear, while others might go for 45 psi all around.

Note that the tires are rated by Bridgestone for a maximum pressure of 44 psi. While this figure has a significant safety margin built into it, please remember that you bear the responsibility for any damage resulting from excessively high tire pressures. Don't inflate the tires to 55 psi unless you you're sure you know what you're doing!

While increasing tire pressure above Honda's 38/35 recommendation can lead to some very impressive mileage figures, there are some other pros and cons to consider:

Pros

• Better fuel efficiency
• Improved road feeling in steering
• Lighter steering effort
• Less strain on powertrain
• Better weight bearing capacity

Cons

• Increased ride harshness and noise. Many see Honda's recommended pressures of 38 front, 35 rear as coming down to a compromise between energy efficiency and ride/noise. Honda's choice of where to put that tradeoff may not be the same as your preference.
• Possible uneven treadwear. While increasing the tire pressure a little above Honda's recommendation shouldn't be a problem, if you go for a tire pressure well above the tire's rated maximum of 44psi, you may find that the tires begin to wear in the center before wearing at the outside. My advise is that if you choose to go with tire pressure significantly higher than the specs, you should monitor treadwear. If you notice uneven treadwear starting, then you may want to back off a little on the tire pressure.
• Less contact patch, resulting in worse handling in wet or snowy conditions.

Conclusion? In many cases it makes sense to increase the tire pressure slightly above Honda's recommendations. This will give you even better fuel efficiency, without having any drastic impacts on ride, noise or handling.

For those who want to do everything possible to improve fuel efficiency, even higher pressures will lead to even further improvements, but you should start to pay close attention to the pros & cons listed above.

TIP: Conserve Momentum

Effort involved / impact on driver: Medium - High

In the city, I find that the biggest secret to getting excellent mileage is conserving momentum. If you just think about when you expect lights to change, other cars to pull into traffic, etc., you can avoid a lot of unnecessary acceleration and deceleration.

The closer you can get to keeping the car at a constant speed, either by changing lanes or not accelerating to too high a speed when you anticipate having to slow down soon, the better you're going to do.

As an added benefit, by actively predicting what traffic and stop lights are going to do, you'll also be driving more safely.

TIP: Use full-throttle acceleration

Effort involved / impact on driver: Medium

You'll get the best efficiency around town by accelerating with full throttle, and shifting up to the next gear quickly, before engine RPMs rise too high.

There are two reason why this works. One is that the higher the gear, the lower the frictional losses. By getting to 5th quickly, the total number of engine revolutions is reduced, with a corresponding reduction in frictional losses. The second reason is pumping losses. This is the work done to force air past a partially closed throttle plate. The more closed the throttle is, the higher the losses. Accelerating quickly reduces throttle losses, because the throttle is open. In addition, engine speed is lower in fifth, so to generate the same amount of power, you have a larger throttle opening (and hence lower throttle losses) - this is another reason to get to higher gears as quickly as possible.

The best fuel economy is gained by a combination of the gas petal to the floor with shifts at as low an rpm as possible to sustain your desired acceleration. This ensures a fully open throttle during the entire acceleration event and gets you out of the lower gears as quickly as possible, for lower frictional losses. It also gives you even more electric motor assist, as the acceleration takes longer. There is only one problem with this technique - its virtually impossible to do. You have to shift like a race car driver, except that the shifts are at low rpm instead of high rpm. You wind up going through gears like a maniac. It can be a lot of fun, but you have to be really involved with driving (no cell phones) and the technique is extremely counterintuitive. The combination of mashing the accelerator and shifting at 2500 or 3000 rpm just doesn't feel right. However, if someone is willing to practice this, they can get a nice boost in FE around town.

After accelerating this way in 1st & 2nd gears, you'll often be up to your desired cruising speeds. Now it is time to switch modes, using as little energy as possible to maintain this speed. Typically you'll now want to be in fifth gear. The 1-2-5 shift pattern (or 1-2-4 as the case may be) may seem strange at first. After all, why are those other gears there if you shouldn't use them? The answer is to think of them as passing gears or cruising at slower speed gears. In most cases, this is the way I use the five gears:

1: Accelerating gear
2: Accelerating gear
3: Even slower cruising / quick passing gear
4: Slow cruising / slower passing gear
5: Cruising gear

Once you're up to speed, in addition to quickly getting into your cruising gear, you'll also want to begin feathering the throttle. Since you should have done all your acceleration before going into cruising gear, you now want to use as light a throttle as possible that will still maintain your current speed. If you find that you want to accelerate further, you may be better to downshift for a quick blip of acceleration, and then shift back into your cruising gear.

TIP: Understand the effects of highway cruising speed

Effort involved / impact on driver: Medium

At highway speeds, the greatest effect on fuel efficiency is the speed that you choose to drive at, coupled with the wind speed & direction.

You'll find that when travelling at highway speeds, the same trip at the same speed will yield different mileage figures one day to the next, just because of variation in wind speed & direction.

Ignoring wind speed & direction (which will average out from day to day), if you want to achieve better mileage on the highway, the best way to do this is to drive more slowly. Of course, there is a tradeoff between driving slowly, and getting to your destination quickly. It is up to you to decide how much, if at all, you want to slow down in order to improve efficiency.

Many owners drive their Insight just as they would any other car. You can still achieve very good efficiency by following the other tips here. However, if you're wondering why you never see the 80 or 90 mpg figures that some owners have achieved, speed may be a major factor.

Personally, I tend to drive at the same speed as other traffic around me. I don't pass a lot of other cars, nor do I give hybrids a bad name by slowing down the traffic behind me.

On the highway, you also want to avoid speeding up or slowing down unnecessarily by predicting what slower and faster traffic will do.

Technical explanation: Highway cruising speed is so important because wind resistance goes up with the square of the vehicle speed and the power demanded from the engine to overcome this force goes up with the cube of the vehicle speed. Fortunately, wind resistance is pretty small at speeds below 45-50 mph, or else this factor would be far more noticeable. However, it really starts taking over at speeds above 65 or so. The gas mileage drops in a hurry.

TIP: Pick a point on the FCD, and aim to stay at that point

Effort involved / impact on driver: Medium

An effective technique for maximizing highway mileage is to pick a point on the Instantaneous Fuel Consumption Display (FCD), and maintain light enough throttle pressure to stay at that point. Once you get up to cruising speed, you'll quickly be able to determine what the lightest amount of gas pedal pressure is necessary to maintain cruising speed. Note what the FCD bar graph reads at this point, and try to maintain the bar graph at or near that point. As conditions change, you may find that you need to adjust the point you're aiming for.

This is a great way to get a second-nature feel for what driving techniques have a big or small impact on your efficiency.

Once you get a feel for this technique and how the car responds to gas pedal pressure, you'll find this becomes second nature, and doesn't require a lot of extra effort.

TIP: Use both miles & kilometers modes on FCD

Effort involved / impact on driver: Low - Medium

If you've always left your Insight's display in miles or kilometers mode (depending on where you live), you should try driving in the other mode from time to time. The Fuel Consumption Display also switches when you switch the speedometer, and each mode gives you a different view of the car that isn't portrayed so accurately by the other mode.

• Miles per gallon mode: Here, the bar graph & number is larger when you're achieving better efficiency (distance over fuel consumed). The graph ranges from 0 to 150 mpg. The advantage of this mode is the extra digit of accuracy and higher resolution of the bar graph allows you to see more subtle differences in the efficiency you're achieving.
• Liters per 100 km mode: Here, the bar graph is & number is larger when you're using more fuel (fuel consumed over distance). The graph ranges from 0 to 12 L/100km. In this mode, you can see the difference between using very little fuel and using no fuel at all, both of which would register as 150 mpg in the miles mode. For example, you can get a feel for when the Insight enters fuel cut mode (not to be confused with idle stop), when no fuel is being consumed at all because the engine is continuing to be turned by the wheels.

(Note that you have to hold down the miles/km button for about 1 second until the display switches modes.)

The illustration below (thanks to Bert Singer) shows how the MPG and l/100km scales correspond to one another:

TIP: Maximize Regenerative Braking

Effort involved / impact on driver: Low-Medium

Maximizing the amount of use you get from the regenerative braking will maximize the amount of "free" electrical power available for later re-acceleration. Also, if you are able to keep the battery level above the 2/3rds point, you can avoid requiring heavy charging of the batteries from the engine at cruising speed, further improving efficiency.

Because the regenerative braking system is limited in how quickly it can slow the car by itself, the more abruptly your stop, the more you are using the friction brakes, and the so the more energy you've wasted. For this reason, it is best to begin slowing sooner, using only a very light pressure on the brake pedal.

Usually I leave the car in whatever gear I was cruising at, using only regenerative braking until the engine gets down to 1000 rpm. At that point I shift into neutral and only using the mechanical friction brakes to bring me the rest of the way to the stop.

More Details:

The Insight's regeneration strategy is dominated by brake feel and driver expectations. The goal is to make the hybrid driving experience virtually identical to driving a conventional vehicle. Thus, Honda did not want the vehicle to unexpected slow down faster than anticipated by the driver. To avoid this, there is a two-step regeneration strategy. In the first step, the amount of regeneration energy is proportional to the rate of deceleration. The idea here is that larger amounts of energy (and hence motor braking) can be done when the customer is expecting the vehicle to slow down faster. This is fairly intuitive and explains why you get more regenerative energy if you downshift (although the same thing could be accomplished by using the brakes to increase deceleration rate). The second step is not intuitive. The computer is programmed to increase the amount of motor braking when the driver activates the brakes. Unlike the first step, this increase is not proportional to how hard the vehicle is decelerating or the driver is braking - it is a fixed increment of regenerative braking. The idea here is that the driver expects the vehicle to slow down when he/she hits the brakes, so the additional motor braking will not be noticed. The cool thing about this is that you don't have to really brake to activate it. If you just barely touch the brakes, you can feel the motor braking kick in even though there is little friction braking. So, anytime you are just coasting down, very lightly depress the brake petal. This is a great way to increase the amount of regenerative braking energy.

TIP: Maximize Use of Idle Stop

Effort involved / impact on driver: Medium

The idle stop feature that causes the engine not to run when propulsion is not needed makes also makes a significant improvement in the Insight's fuel efficiency.

Idle stop will activate when you're decelerating, typically when your speed falls below 30 km/h or 19 mph, if you are in neutral or your foot is on the clutch in any gear other than 1st or reverse. This means that you don't want to sit at a stoplight in 1st gear, as the engine will continue idling. Personally, I sit at the light with my foot on the clutch, and one hand on the shifter. This allows me to shift into1st and take off just about as quickly as if I had left the transmission in 1st.

When my battery level is at or near full charge, I put priority on idle stop rather than regenerative braking. So, rather than decelerating slowly, I decelerate relatively quickly to the 30km/h / 19mph auto stop threshold. As soon as the engine stops running, I'll often take my foot entirely off the brake, and continue to coast towards the red light ahead. Not only am I moving without the engine running at all, but by continuing to move slowly, I maximize the chance that I won't have to come to a complete stop before the light changes to green. This in turn further improves fuel efficiency.

While this takes a little practice at first, it soon becomes second nature, and really helps with fuel efficiency.

Other situations where you can encourage it to entire idle stop is in stop and go traffic, or when going down hill slowly. The best situation is when in stop and go traffic while going downhill. Here, you can just release the brake and start coasting without running the engine at all. One thing to remember is that idle stop won't happen when you're in first, which is typically the case in stop and go traffic. You'll have to switch into neutral to get idle stop to happen in this situation.

Also, since the power brakes are fed off intake manifold pressure, continual applying and releasing of the brakes in the downhill stop-and-go traffic situation will "use up" master brake cylinder pressure. The Insight is smart enough to restart the engine automatically to continue to provide brake pressure. Typically you'll get three or four brake applications before this happens. Once this happens, the Insight may not return to idle stop mode until it next sees you applying gas in some gear to accelerate.

Note: When coasting, you may notice that if you don't keep your foot on the clutch, the engine will sometimes restart when you release the brake pedal. For this reason, I tend to keep my foot on the clutch, even when in neutral.

TIP: Drafting

Effort involved / impact on driver: High

Drafting is following another vehicle - typically a large truck - very closely, to reduce the amount of aerodynamic drag that your car experiences. Drafting very closely to another vehicle is dangerous, and I don't encourage the practice. However, there is no denying that drafting can lead to very good fuel efficiency numbers.

TIP: Surfing

Effort involved / impact on driver: High

Submitted by: Tim Duggan

In addition to drafting, one can also "surf". I have found that large trucks (esp. cab-over's) can produce a fairly nice wake. The trick is to stay in an adjacent lane just far enough ahead so you are not taking the air blast to the side. The technical aspect of this is as follows.

1. The motion of the vehicle creates a vacuum behind it as air rushes around the back of the vehicle to replace the void created where the vehicle once was.

2. Air flowing around your vehicle travels faster than the vehicle itself, since it must go around the vehicle and fill the void.

3. The only thing accelerating and moving this air is the vehicle.

4. The larger the vehicle, the larger this effect is. So why not use part of the air being displaced by a large truck to fill the tiny void behind your car.

My experience shows a gain between 5 and 7 mpg. It seems fairly easy since you don't actually have to watch the truck constantly. You will know by feel if you are pulling ahead or falling behind (chances are you won't be pulling ahead if you are feathering the throttle right). So the upside is mpg (and no ticket for riding too close) the downside is you can get blown around a bit. So go surfing, just don't get caught in the undertow!