Fuel leak?

13hondacivic

Alright. My 2013 civic. I'm taking it in on Saturday once again. I filled up my gas tank yesterday and im now down to half. All of the driving I did with the full tank was from the gas station to my house, then to work. Car says I'm getting 33.6 mpg which is absolutely impossible. I see nothing under the car. Can you have a leak internally? I figure I have to be pouring gas out somewhere.

iamgumby

How many miles from gas station to house, then to work? Have you calculated your actual gas MPG by filling the tank, logging miles, running until fuel is needed again, and dividing actual miles traveled by gallons used? I know it is the old fashioned way of doing it, but it is real information. Not a computer generated optimistic calculation designed to make the customer feel good.
If your trip was short and used a half tank of gas, the engine would have been running very rough, smoking black, eventually fouling the spark plugs to the point it would no longer start. If it leaked half a tank of gas, you and everyone for several blocks around would have smelled it. If the engine had an internal fuel leak, the oil would be way over the full mark, and very likely getting pushed out past the seals and gaskets onto the ground.
There are 3 logical possibilities. 1. When you filled the tank it was not actually full even though the gauge said it was. 2. The gauge is malfunctioning, and there is more than 1/2 tank left. 3. Someone siphoned gas from your tank.
I don't know if Honda still does it, but they used to have a drain plug in the bottom of the fuel tank. It makes it real convenient for someone to just remove the plug and drain out as much fuel as they want. Only a "nice" gas thief puts the plug back in after they are done..

13hondacivic

well I noticed that my gauge was going up and down so I took it to mieneke and they said my fuel sending gauge is failing. So essentially I really don't know how much gas I have. But I still feel like I'm putting in more gas than I should be and not getting the gas mileage that it says I am, which is 33.5 mpg. So I'm still confused I guess.

13hondacivic

I didn't take it to Honda because they don't know what the heck their doing and make me out to be incompetent every time I go in there.

iamgumby

If you have not yet replaced the sending unit, there is a possible "cure" that you can try. Get a bottle of Chevron Techron fuel injector cleaner (available at Auto Zone and other auto parts stores) and add it to the fuel tank next time you fill up. The sticking sending unit may be caused by fuel deposit build-up on the unit, which will be removed by the injector cleaner. I have fixed 2 Corvette fuel gauges this way, and both have been working fine for over a year now. Even if it does not fix the fuel gauge, cleaning the injectors will help improve fuel mileage by removing deposits from the injectors.

Dashboard MPG displays are inherently optimistic. Manufacturers know that most people will not "do the math" if the car does it for them, so they prefer to err on the higher MPG side to make the customer feel good about their great fuel mileage. If you want to know the REAL MPG, keep a log book and enter the mileage and gallons every time you fill up. Subtract last fill up miles from this fill miles. Then divide that answer by the number of gallons added this time. That will give you the true MPG for that tank of gas. Put that in the log book also. Do this every time you fill up, and you can see your real MPG average over time. The longer you do this, the more accurate the average will be. For example, if you did this 5 times, you would add all the MPG figures together, then divide by 5, giving you the true average MPG figure. This is also great to monitor for a change in average MPG which might indicate something is starting to go wrong. (like injectors getting dirty or spark plugs wearing out) This happens slowly, and usually goes unnoticed.

While on the subject of fuel economy, do not forget to keep an eye on tire pressures. Tires will loose several pounds of pressure per month, and under inflated tires require more power to roll, hence more gas used. You can not look at a tire and see that it is under inflated until it is so low that the tire is being damaged from excessive sidewall flexing. This can cause a life threatening condition such as a blow-out or what is referred to as a zipper rupture when you fill the tire back up. The excessive sidewall flexing causes the wire cords in the tire to break, and it can blow out the sidewall while you are refilling the tire. This can have deadly results. In this case an ounce of prevention is worth several hundred pounds of cure.

I am a Certified ASE Master technician with over 42 years experience. Most technicians are honest, and try their best to do what is right for their customer. However, there are some that are just in it for the money, and will do whatever they can to increase their bottom line. I believe that you will find more of the bad ones at the "stealerships" than at the privately owned repair shops. Any shop that fails to treat their customer with respect, doesn't deserve either one. Just my 2 cents worth...