Improving Your Mileage
Understand your Mileage
Mileage versus Gear
|The chart to the right depicts
the mileage (miles per gallon of fuel, or mpg) possible in each gear, under
The worst mileage is in 1st gear (max power to the wheel).
gets progressively better with each up-shift to a higher gear.
Best mileage is in top gear (5th gear in this chart).
Acceleration versus Mileage
Another important factor that affects mileage is how heavy your foot is
on the accelerator (the gas pedal.) The more you depress the
accelerator, the more power the engine produces, and the more fuel it uses.
We look at accelerator use in the next three panels, below.
The blue dots at the intersection of each torque curve with the next
higher gear is where the shift point would be for maximum power and
In an automatic transmission vehicle, the driver would floor the gas pedal
and keep it there. In a manual transmission vehicle, the driver would
shift gears at red-line.
Unfortunately, shifting gears at the maximum point is also the
worst possible fuel economy. It is also
very hard on the engine -- so hard that race car drivers often choose to
rebuild their engines after every race,
This graph, to the right, displays the same possible torque curves for each
gear, but we have moved the shift point to the maximum torque point for each
The blue lines represent what portions of each torque curve would be
utilized, and the blue dots and vertical dotted lines represent the shift
This would produce a brisk acceleration to speed, and a much improved fuel
efficiency over the previous pedal-to-the-metal race car style.
When you are driving in traffic, especially commuter traffic, other drivers
expect you to keep your speed up, or they tend to go into road rage.
So a polite driver is more or less forced to drive at a brisk rate.
Maximum Fuel Efficiency
This graph, to the right, displays
the same possible torque curves for each gear, but we have moved the shift
point further to the left of maximum torque point for each gear.
The red lines represent what portions of each torque curve would be
utilized, and the red dots and vertical dotted lines represent the
The strategy here is to minimize fuel usage by shifting up to the next gear
as soon a possible (without stalling the engine.) And to stay in top
gear as long as possible before having to shift to a lower gear.
Unfortunately, up-shifting at the soonest point can also produces an anemic
acceleration to speed.
Done in the extreme, such as often done by extreme hyper-milers,
such slow acceleration as done under Maximum Fuel
Efficiency, above, can result in road rage from other drivers caught
behind him (or her), as this type driver takes an extremely long time to
accelerate to normal traffic speed.
When you are in normal traffic, accelerate more briskly to flow with the
traffic. But when you can, take your time accelerating.
However, in congested "Stop & Go" traffic, you are often forced to just poke
along, with the long line of impeded traffic contracting and expanding by
cars speeding up then being forced to slow down, often forced to stop
intermittently. In that situation, it is better to pace
yourself, with very mild accelerations when the opportunity arises to speed
up a little, and try to avoid speeding up and slowing down.
Selecting routes which allows you to avoid traffic lights and stop signs
whenever possible also is a good strategy -- it helps you avoid having to
drive in lower gears (with higher fuel consumption rates.)
Generally speaking, you will get much better fuel efficiency (mileage) on
highways than driving in the city traffic, even at elevated highway speeds.
© 2014, Simon R. Mouer III, PhD, PE
All rights reserved.