Questions and Answers
Civic Drops MPG
Q. My Civic seems to have dropped fuel mileage lately. I bought the car new and would get 40 mpg on the highway and 34-36 in the city until about 70,000 miles. Currently I get 30 mpg, consistently; so I am seeing a drop of about 4-6 mpg or about 14% reduction.
I have a new set of Firestone Firehawk SS20's with proper pressure and rotation. Otherwise, the engine is properly maintained, including regular oil/oil filter changes, spark plug changes and air cleaner element.
I do need to change the anti-freeze.
What's causing the reduction in MPG? Do I need to have the injectors cleaned? Plug wires changed? (Can't find anything in the manual about changing the plug wires.)
1997, Honda Civic HX
Manual transmission
78,000 miles
Fuel Injection
Standard Power Assisted
P/S, A/C, P/WThanks,
BobbyA. Well first off, at 78,000 miles I would replace the ignition wires. There is no set schedule for replacing them but the time and milage would indicate that they can use replacing.
As for the drop in milage, it could be the tires that has caused the drop. Some tires "roll" better than others and thus require less fuel to move the vehicle. The biggest factor in a tires rollability is the tread pattern. A tire with an aggressive tread pattern will have more resistance than a tire with a less aggressive pattern.
Another reason for the drop may be that the engine is getting older. As an engine ages milage will drop due to internal wear. You might want to have the engine scanned to make sure everything is still within specs and that all the sensors are operating normally.
Basically you have done all that you can to keep the car in good shape and you'll get many more miles out of it. It just won't be as efficient as it was when it was new.
Additional Information provided courtesy of ALLDATA
