Driving for MPG

It’s all about managing your power. As mentioned above, you will need an electronic readout to know the precise location of your right foot. The TPS reading in the KR ScanGauge will give you the current Throttle Position from 0 to 100%, or you can watch the instant mpg, load %, gph (gallons per hour) or even a horse power reading. A trip meter with an average mpg is also a must. It acts as an incentive and will help you judge where to set your throttle. I have my KR ScanGauge driving screen set up with the instant mpg, instant hp, throttle position, and trip mpg. That way I know where my foot is at all times and can use the trip mpg as a reference or goal to beat.

Some of the old timers used the boost gauge and pyrometer for this because it was the best they had. It actually did a pretty good job but wasn’t as precise.

Because your speed will vary a little more than in a normal driving style, some of the following driving techniques should be used with discretion. Especially in high traffic areas. Don’t be a pain to the drivers around you just to get a little higher mpg. That said, the variation in your speed will not really be much different than someone pulling a heavier load or running a smaller engine so you don’t really need to be bothered by having someone pass you on the hills.

Over-the-Road Hypermilers will tell you that the most important fuel saving technique is learning to control the right foot. Holding it steady rather than putting the pressure to it while coming into a grade is almost impossible at first but well worth the effort to learn.

When traffic permits the Hypermiler style of driving described below can improve your mpg by at least a half mile per gallon, usually more.

Driving tips:

I use my average trip mpg reading to detect what my “road load” is. “Road Load” is the force or power required to propel a vehicle at any moment in time. These forces include tire rolling resistance, aerodynamic drag, acceleration, and grade effects.

Your average trip mpg will be very close to the same mpg and TPS reading as when you are on a flat stretch of highway. Using that as a target, resist going past that throttle position even if you lose some speed on the uphill grades. Allow the truck to slow on uphill grades and gain speed and momentum going down.

For demonstration purposes we’ll use a load that requires 6 mpg at 68 mph. If you hold your throttle position steady you will lose about .3 mpg every time you drop a gear. Keep it in the highest gear practical for your load and resist the urge to downshift until you reach the low end of the torque curve for your engine, usually around 1200 rpm.

With the gear drop and the speed loss you may lose as much as 1 mpg over the distance of the climb, dropping to 5 mpg. A cruise control on the other hand, would have you at Wide Open Throttle (WOT) trying to maintain your set cruise speed and have you sucking 3 mpg or more, a 40% decrease in mpg over the length of the same climb.

The goal is to crest each hill at or above 55 mph while using the least amount of throttle pressure and as few gear changes as possible. A good thing to keep in mind is that there is not a hill in the US that requires more than 300 hp to climb and a 300 hp engine will only consume about 15 gph at WOT.

If I’m heavy and running though terrain like WV for example and know I will need full throttle to crest the next hill I will drop a gear a little sooner (around 1350 rpm) while maintaining the same throttle position and then start down shifting earlier as my speed drops but still not using full throttle until my speed has dropped to below 60 mph. Sometimes the total road load requirement just won’t let you take full advantage of the trucks momentum because the grade is too long and you’re going to be at WOT before you reach the top anyway.

On a 440 hp engine the WOT fuel consumption is somewhere around 22 gallons per hour. WOT at 60 mph calculates to 2.7 mpg. In many instances you can crest the grade at a reasonable speed without increasing the throttle position, thereby not dropping your mpg fuel mileage below 5 mpg. You will have gained 2.3 mpg (5 - 2.7 = 2.3) on the distance of that climb, definitely worth it even if it was a little slower during the climb. It’s much better to make up that time on the downhill side and gain a little momentum for the next uphill grade.

Watch your readouts and try to keep your instant mpg above the trip mpg. Your trip mpg will continue to gradually improve throughout the trip.

When you drop off a hill remember to back off the throttle completely just before you reach your desired speed as long as the grade is sufficient to give you some momentum for the upcoming grade. Unlike idling, where your fuel consumption is .6 to over 1.0 gph the fuel rate will drop to 0 gph with the throttle in idle position at highway speeds. This technique will also save fuel and brakes whenever you need to slow for exit ramps, stop lights or traffic. It’s all free miles, 0 fuel.

While the above techniques will improve your mpg they do require making a conscious effort and are almost impossible to apply in all driving conditions. The “Power Manager” described in the “Products” section of this web site makes it possible and has shown impressive results.

Brake less, coast more (but make sure you are in gear with the clutch engaged or it will go to idle consumption and waste a 1 gallon of fuel per hour). Remember if you waste a gallon of fuel it’s like throwing away 20 horse power.

If you gain ½ mpg on a truck currently getting 6 mpg, and run 125,000 miles a year, you can save 1,600 gallons a year. At $2.50 per gallon, that’s $4,000 per year.

As stated above, using a cruise control will cost a Hypermiler fuel. The cruise control saves fuel is by eliminating over-fueling at speeds above the cruise set speed that commonly occur when using the foot throttle. It also eliminates the constant motion of the driver’s foot while using a manual throttle and bouncing down the road. The computer senses every little motion and the average throttle position is higher.

The reason Hypermilers can beat the cruise control is because they will allow their speed to droop or slow on the grades while the cruise control will throw more fuel at it in an effort to maintain the set cruise speed. In many cases if you will maintain a steady throttle position and allow the truck to slow 5 to 10 mph on a grade you will save 25% on fuel while climbing the grade.

If you must use a cruise control be sure your ECM parameters are set to maximize mpg. Setting the Lower Droop to 0 will shut off your fuel as soon as you reach your cruise speed setting and allow you to roll over the hill with less likelihood of needing the brakes before you reach the bottom. Setting your upper droop to 3 mph or more will allow your speed to drop 3 mph before adding fuel to maintain your set cruise speed when coming into a hill. This way you use some of the truck’s momentum before adding fuel to maintain speed on the up side of the hill. This will help some when using a cruise control in rolling hills like I-80 in IA and many other US interstates.

Also, some ECMs have two settings for the accelerator. The ‘Automotive Accelerator’ setting gives you a more precise control of fueling much like the throttle in your car while the ‘Variable Speed (VS) Governor sometimes call ‘All Speed Governor’ acts more like a governor or cruise control and will add fuel without moving the throttle as it tries to maintain the current speed with less foot interaction. In my opinion the Variable Speed Governor setting will make it harder to precisely control your fuel savings while driving for MPG.