hello, My 07 Prius is now at 105237 miles. I used to get more than 55 mpg on highway. However, just lately I always get below 45 mpg. I am thinking of changing the spark plug now. Is it the right thing to do? Please also recommend spark plug which fit well with Prius. Other than spark plug, what else should I focus on? Thank Salen
use the oem plugs. clean the throttle body, check your tyre pressure and test the 12 volt battery. keep in mind, cold weather, slushy streets and winter gas formulation all work to reduce mpg's.
Changing plugs at 100K miles is a good idea and the recommended change interval. However, the most common and most overlooked cause of dropping fuel economy is poor wheel alignment.
Wheel drag might also cause a drop in mpg. Could be misalignment, as mentioned above, brake neglect causing drag for one reason or another, or even low tire pressures.
