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We recently purchased a Subaru Forester and were expecting to get about 24 MPG in the city. So, we were shocked when the fuel efficiency was averaging about 18 MPG. I searched the Internet and discovered other people were having a similar experience. There wasn’t much advice offered online. In a discussion forum on this topic, one owner stated that it might be necessary to break-in the engine over about 15,000 miles and then the fuel efficiency would improve.

I decided to do a little testing on my own. After a few modifications in how I was driving, I started seeing 25 MPG in the city.

Seven Tips for Improving MGP Fuel Efficiency

Here’s what I discovered can make a big difference in fuel efficiency:

  1. Slow Starts. Some cars have an Eco Mode that makes a car slow to respond. With our Subaru Forester, the driver needs to be mindful when pressing on the gas. The powerful Subaru boxer engine combined with responsive handling and precise cornering made me want to drive a little more zippy than any previous car I’d owned. Other cars were more sluggish, and so I wasn’t inspired to zip ahead.
  2. Slow Accelerations. There are times when fast acceleration is necessary such as getting on the highway or passing a vehicle. However, if you can accelerate slowly most of the time, this will equate to greatly improved fuel efficiency.
  3. Cruise Control. We tend to think of Cruise Control as something to be used for highway driving. However, with city driving it’s a great tool to improve fuel efficiency. It’s important not to let cruise control give you a false sense of security. In the city, it’s just as important to be alert and aware of your surroundings. However, for stretches of road when frequent stops aren’t required, Cruise Control will be better than the slight speeding up and slowing down that we all tend to do when driving.
  4. Reduce Breaking. When you use the breaks in a non-hybrid car, you’re simply converting the power of fuel into worn out breaks. The gas you used to speed up, is now being wasted in breaking. Instead, if you can keep your eyes on the road ahead of you, perhaps a greater distance than you normally would, it’s possible to let off the gas early enough so that the car naturally slows down when approaching a stop. This way, the full amount of fuel energy is used in forward motion.
  5. Use Trip Odometers. Most cars have a Trip A and Trip B odometer, in addition to the main odometer. If you use Trip A for in-town driving, and use Trip B for highway driving, this will help you get a sense of what your average MPG for each driving situation. It’s common for cars to have an Average MPG displayed based on a specific trip odometer, so you’ll get a handy readout of each. Then, for your overall average MPG, you can calculate that at the fuel pump by tracking the miles since your previous fill-up and dividing by the gallons required to fill up.
  6. Drive 55 When Possible. Most cars have a fuel efficiency sweet spot. When driving that speed continuously, and using cruise control, you’ll be amazed to see that your car is able to get 40 to 50 miles per gallon. For most cars this happens at 55 MPH. If you drive faster than that, or slower, you’ll get worse fuel efficiency. If we could all drive 55 all the time, then everyone would get amazing gas mileage. It’s the in-town slower driving, and 70 MPH highway driving that really causes a decline in the average MPG.
  7. City Driving Varies. Some cities, like Cedar Rapids have stretches of road where there are few stop lights, and the speed limit is higher. In Iowa City, when driving downtown it’s not uncommon to have many starts and stops. So, ‘in-town’ fuel efficiency will vary significantly depending on the driving conditions. Try to choose routs with little traffic, few lights, and with higher speed limits.

Insights

Here are a couple of insights that helped me arrive at the above list.

  1. Years ago, we purchased a Garmin Nuvi GPS system. We were driving a Toyota Corolla at that time. The Nivi had an Eco mode where you enter the vehicle make and model, then it suggests routes that will result in the optimal fuel efficiency. Those tended to be back roads with speed limits of 55 MPH. It was amazing to see the Corolla get 40 to 50 miles per gallon consistently at those speeds. It changed how I approached highway driving. That experience came to mind when working to improve our Subaru Forester fuel efficiency.
  2. We currently have a Honda CRV in addition to the Subaru Forester. The Honda CRV has an Eco Mode that we use most of the time. Occasionally I’ll take it out of Eco Mode for extra performance when getting on the highway. In Eco Mode, when you press on the gas pedal, the car considers it more like a suggestion rather than a command. Regardless of how erratically you give it gas, the car tends to slowly startup. When not in Eco Mode, the Honda CRV really takes off quickly and is more responsive to the gas pedal, allowing the engine to reach about 6,000 RPM before shifting. It’s a quick way to get ahead fast, but it does result in lower fuel efficiency. In fact, I was reminded that our Honda CRV gets about 18 or 19 MPG when we don’t use Eco Mode.

Questions?

If you have any questions, feel free to contact me using the contact page.

20110920tu-greg-johnson

Greg Johnson, Facilitator
Iowa City Subaru Club