Questiongetting bad gas mileage replaced plugs,wires even ran injector cleaner multiple times,still 18mpg.
AnswerHi, Kancep. The problem with trying to correct low fuel economy is that there are so many possible causes, it's a daunting task just attempting to find a cause. Unless your spark plugs are misfiring or your wires are arcing, replacing them won't affect your fuel economy. Not only will injector cleaning chemicals not improve your fuel economy if your injectors are not partially clogged, I've never even seen any indication that most injector cleaning products readily available to consumers even do an effective job of cleaning injectors.
Is your check engine lamp on? If so, you should start by having this diagnosed. Many issues that will cause a check engine lamp to illuminate will also cause poor fuel economy.
Next, I typically like to examine the type of driving done. Checking the EPA estimates for this vehicle, the rated city fuel economy is 21-22 MPG. If you're doing city driving nearly exclusively and/or you drive aggressively, then 18 MPG doesn't seem far enough removed from the EPA rating to cause me concern. If you're doing mostly highway driving (steady speed 50-70 MPH with little slowing/accelerating) and driving the vehicle somewhat easily, then I'd have some concern regarding your fuel economy in comparison to the EPA rating of 30 MPG.
If you're still of the opinion that your fuel economy is poor, then there are a few more things you can check yourself.
-- Does the engine provide the proper amount of power? Does the car accelerate properly? If not, the cause should be diagnosed.
-- Are your tires inflated to the recommended pressure on the door jamb or up to a few PSI above that? Low tire pressure will reduce fuel economy.
-- Does your vehicle track straight? Do you have abnormal tire wear patterns? An improper toe setting (alignment issue) can cause poor fuel economy.
-- Does your transmission shift normally into all forward gears? If an automatic, does the torque converter clutch engage at steady speed driving of 50MPH and above? Excessive engine rpm can cause poor fuel economy.
-- Are you carrying a lot of weight in the car? This will reduce fuel economy.
Beyond this, there's probably little you can check yourself. A shop with a scan tool capable of reading the engine management data stream will be able to check additional items. But if your check engine lamp is not on, this indicates the engine control module (ECM) ahs not noticed an abnormal condition and means it is also unlikely the shop will see anything abnormal in the data.
In addition, my experience is that shops tend to use poor fuel economy as an excuse to sell tune-ups, injector cleanings, top engine cleanings, air filters, fuel filters, and other services which will not improve fuel economy if there is no actual problem. If you cannot detect any of the potential issues I've mentioned above, the chances of a shop finding an actual problem causing low fuel economy are very small.
