Causes of a Difference in the Gas Mileage for a 2007 Toyota Yaris
According the the Department of Energy, the average reported -- or real-world -- fuel economy rating for the 2007 Yaris spread over a stunning 26 mpg; from 23 mpg all the way up to 52 mpg, with an average of about 39 mpg. This reality of economy-car ownership sheds a whole new light on those neat 29 city and 36 highway numbers posted on the car's window. The reasons for this massive gap are manifold, and probably have as much to do with you and your driving conditions as with the car itself.
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Transmissions
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Despite advancements in automatic transmission technologies, the traditional manual gearbox remains the most efficient means of transferring power from flywheel to drive wheels. Manual gearboxes don't contain a torque converter, high-pressure oil pump or drive clutches, all of which suck up a certain amount of engine power. According to official EPA estimates, the manual Yaris rates an additional 1 mpg on the highway over the automatic Yaris. The real-world results for users reporting to fueleconomy.gov indicate a more impressive 3 mpg average gain; 38.2 manual mpg versus 35.1 for the automatic.
Extra Weight
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Even with its small stature and fairly low 2,300-pound curb weight, the Yaris is no bantam once wheels hit the tarmac. Its 106-horsepower engine is fairly sufficient if you're looking at hauling nothing but the weight of the car and a single 120-pound driver; but start adding multiple passengers, cargo and drivers who weigh more than a tiny ballerina, and the little engine that could suddenly can't anymore. This extra mass puts a lot of strain on an engine that was only adequate on its best day, and which lacks the torque to accelerate and climb hills without shifting to a lower gear.
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Driving Style and Conditions
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It's not about what you drive; it's about how you drive it. This is particularly true of small, underpowered cars such as the Yaris, which depend upon momentum to maintain decent fuel economy. The BBC's award-winning automotive program "Top Gear" once tested the fuel economy of a Toyota Prius -- which, incidentally, uses an engine almost identical to the Yaris' -- against a 400-horsepower BMW M3. "Top Gear" performed its test on a race track, with the Prius being driven as quickly as possible and the BMW driven just fast enough to keep up with the Prius. The result: Flogging the Prius to death returned 17 mpg, while simply cruising the Bimmer at the same speed netted 19 mpg.
Tires
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The Yaris draws from the heritage of its Toyota Vitz cousin, which has had its own racing series in Japan for more than a decade. The Vitz/Yaris is a sporty car, at least in terms of nimble handling and being lightweight, and Toyota's choice of tire reflects that. The Yaris' original-equipment Bridgestone Potenza RE92 uses a construction and rubber compound engineered for responsive handling, cornering grip and high-speed stability, but makes those gains come at the expense of rolling resistance and fuel economy. Five or more years after the car's original purchase date, odds are even to good that your car no longer uses those fast-wearing and somewhat pricey Potenzas. You or a previous owner may have traded them out for more durable and fuel-economy-oriented tires, which affects the car's overall mpg performance.
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References
- Race Car Engineering and Mechanics; Paul Van Valkenburgh
- Family Car: 2007 Toyota Yaris 4 Door Sedan and 2 Door Liftback
- Fueleconomy.gov: 2007 Toyota Yaris
- Tire Rack: Bridgeston Potenza RE92 Specs and Surveys
Resources
- Photo Credit Thinkstock/Comstock/Getty Images
