Gas Mileage on a 2009 Toyota Yaris



Any ideas why I only get 25-26 mpg with my 2009 Toyota Yaris? My mechanic (whom I trust), has adjusted the computer but has no other ideas. I live in Seattle, which is pretty hilly.


There’s no way to adjust the computer–or any other part of the fuel control system–on your car so something must have been lost in translation from your mechanic to us.

What was your gas mileage a year ago? How are you determining gas mileage? When do you get this 25 mpg. I’d expect mid 30’s on the highway at a steady cruise at 70mph. I’d expect 25 (maybe even less) if all you do is short distance driving in hilly Seattle.


Have you checked tire pressures? How many miles on the car? As asked, is this a new drop or been like this since 2009.


The EPA estimates 29 MPG for city driving. Their estimate is not 100% city, and if you only do city or rush hour bumper to bumper driving the mileage might be about right. A few drivers reported similar mileage at Let us know what percentage is city and how much you sit in traffic. Winter blends go gasoline also drop the mileage about 10%.


I agree with all the former comments. Fuel economy is affected by the way you drive and the location in which you drive. My wife always gets better fuel economy when driving than I do. We used to live in the Seattle area and fuel economy was always worse there than the area we left…flat Wichita, KS. I think your 26mpg is right on the money provided your tires are at the proper pressure.


+1 to all of the preceding comments.

I REALLY hope that the OP simply misunderstood what the mechanic said, because if he really did say that he adjusted the computer, then he is lying. Whether that lie was to extract a fee for work that was not done, or simply to get rid of the customer for the time being, is impossible to determine from a distance, but the bottom line is that the “computer” is not adjustable–as asemaster pointed out.

Hilly terrain can definitely have a negative impact on gas mileage, as can the way that people drive. As an example, when I drive my friend’s Rav-4, I can wring at least 2 mpg more from a tank of gas than he can. The major difference is that I don’t go directly from the gas to the brake pedal unless there is an emergency situation. Coasting for some distance before braking can really help with gas mileage.

The ways to achieve maximum gas mileage include:

Keeping the car in excellent mechanical condition. (Is ALL of the maintenance up to date? Is the motor oil the same viscosity as Toyota specifies?)

NOT warming up the engine before driving. (The engine actually warms-up faster by driving very conservatively for the first few miles.)

Never using drive-up windows at banks & fast food joints. (Your waistline will benefit from this also.)

Keeping the tires inflated to at least the pressure that the car mfr recommends. The recommended pressure is listed on a label affixed to the driver’s door jamb. (Inflating the tires to 3 or 4 lbs over the car mfr’s recommended pressure will help slightly to improve gas mileage, although it can produce a slightly harsher ride)

Making believe that there is a raw egg between your foot and the gas pedal/brake pedal. (If you want to avoid crushing that egg, you have to use very gentle and gradual applications of both pedals.)

Making sure that you are not carrying around excess junk in the trunk.

Making sure that you plan your drives in order to combine errands. Instead of taking 3 separate short drives to do your errands, learn to combine them in one efficient pattern, so that the engine never has a chance to cool-down fully between stops. (When an engine operates at or near its normal operating temperature, it will be more economical than when it is run while cold.)


I have a 2008 Yaris and I seldom get less than 40 mpg. Most of those less than 40 mpg tanks occurred on long highway trips against a really adverse headwind.
The less you use your brakes, the better your gas mileage will be. With practice, you too can spot red lights from as far as a quarter mile away and coast towards them instead of continuing at your normal speed only to stop at the last second, coming to a complete stop only to have the light turn green right after you stop, had you coasted, you would not have reached the light early enough to have to stop and you would just have resumed your speed. Less energy expended approaching the light and less energy expended to re-accelerate the car.
As a side benefit, after 110,000 miles, my OEM brake pads still have over 60% of their lining left.


All of the above comments are relevant.

I would ask the shop if they have checked your coolant temperature sensor and analyzed your fuel trims for signs of weirdness.

I would also be sure that you are calculating MPG using mileage from the odometer and gallons pumped as shown on the fuel pump. If you really want to know, don’t trust the fuel gauge or in car computer display (if you have one of those).


Computer display on a Yaris? Mine has an analog speedometer, fuel gauge, clock, and idiot lights.
These are basic transportation, the windows even open with cranks.


As said above, it is hard to tell whether your mpg is below what it should be or not. It depends on many factors. But if the same driver is driving the same places and the mpg drops suddenly, my first suspect would be either the engine isn’t getting to normal operating temperature – usually due to a stuck thermostat – or the ECM is not reading the coolant temperature incorrectly – usually do to a faulty coolant temp sensor. After that … hmm … dirty air filter, faulty fuel pressure regulator, spark plugs need replacing, etc …