Hi All
I have a 2001 hyundai elantra which I think is guzzling lots of gas. Just out of curiosity, is it reasonable to expect a car maintain its mileage rating as it gets older (assuming that the car is well maintained etc…etc). IF not, how different mileage rating will get (on average).
Anyway my problem is that I am getting worse and worse mileage for my car. It seems like I can see that the fuel gauge move (down) while driving even after travelling just around 6-7 miles. I noticed that this gas usage is worse when there is a lot of hill climbs and fast acceleration in a stop/go traffic. If I was to be maintaining steady speed, then the usage is more reasonable.
I regularly have the car serviced and looked into the obvious stuff (e.g. changing air filters and tyre pressure) but it does not seem to make any difference. I even tried using those fuel system cleaner additive (the one you add to the gas tank) to clean the injectors ect. It seems to work for a while the effect is gone after refilling. Does anyone have suggestions what I should check ? Injector leaks, oxygen sensors?
thanks
You should start by checking your mileage. You do that by filling the tank and noting the miles on the odometer. Then drive normally until you need fuel again then fill the tank recording the miles and the gallons again. Subtract the first odometer reading from the second and divide the result by the number of gallons added at the second refill.
Right now you are the doctor who has not even taken the patient’s temperature yet.
A competent engine computer scan and evaluation, by a competent mechanic can determine if any of the sensors, or actuators, are off. They (sensors and actuators) can be off without causing codes to set.
Have you measured the mileage? What is it?
If you haven’t measured the mileage how do you know you’re using more or less than before?
All cars get less mileage in stop-and-go driving than steady speed driving. This is normal.
The fuel mileage for a car should not change drastically as the car ages. If it does something is wrong.
Does the temp gauge come up to normal promptly? After 8 years it’s due for a new thermostat.
It is perfectly normal for a fuel gauge to show a rapid drop under certain conditions. Most cars will do this. It is not a true indication, however, of actual fuel consumption.
Most likely there is nothing wrong with your car. Don’t offer your car to a mechanic for costly repairs based on this assessment. Your car will be returned to you in tip-top condition and you will still see the same behavior of your fuel gauge.
As others have said, take the trouble to determine actual fuel consumption by long-term record-keeping. Then you can decide your next step,if any.
I don’t think a drop in fuel economy is normal. My car is 11 years old and gets the same amount of gallons per mile as when it was new. Notice I didn’t say “miles per gallon,” since gallons per mile (or gallons per 10,000 miles) is better for comparison.
You need to take some measurements by tracking your fuel usage and odometer readings when you fill-up. You should expect some fluctuation since you can’t rule out all the factors that affect fuel economy, but the GPMs (or MPGs if you insist on using this number) should not fluctuate too much.
how many liters per 100 kilometers is that? 
In addition to the type of driving you do, gasoline mixtures and maybe outside temperature can affect mileage. A decade or so ago, I owned a Mazda GLC that always got between 30 and 40mpg when I drove it in California … even with a fair amount of city driving. When I moved to Michigan and Winter arrived, the mileage dropped to 18 mpg. I don’t know how much of the decrease was temperature and how much was gasoline mix.
The gasoline-ethanol mixtures that are popular nowadays probably cut mileage also. Ethanol has substantially less energy per gallon than does gasoline.
No, it is not normal for gas mileage to worsen as a car ages. As an example of this, my gas mileage actually improved by about 1.5 mpg some time after it passed 90k. Apparently, it took that long for the engine to “loosen up”, but then again, I do maintain the car better than is specified by the manufacturer, and I usually drive it gently.
Another point with which I would take issue is the OP’s statement, “I can see the fuel gauge move (down) while driving even after travelling just around 6-7 miles”. The fuel gauge is not a laboratory-grade measuring device, and is only an approximation of what is contained in the tank. And, most fuel gauges do not move in a linear fashion, so the rate at which the needle drops is not of significance.
As was suggested, the only way to determine what is going on is to:
Actually calculate the gas mileage, preferably over the course of at least 3 fill-ups.
Have the engine checked by a competent mechanic if the fuel mileage really is “off” by a major extent.
I was also thinking Coolant Temp Sensor - so that should be checked too.
(If the engine runs too cool, or the computer “thinks” it is running too cool, it will always run rich - too much gas, as if it still needs to be warmed up).