Gas mileage cut almost in half!!! what could it be??

[askingxforxit]

Have you verified that the gas Gage is correct and not giving you a false reading. I'm not sure about the Fuel pumps on the X but i know on some trucks that an early warning sign that the fuel pump is going out is a floating/non working fuel Gage. My X's gas Gage is kinda retarded. One moment Its looking like at a half a tank I'm getting terrible gas mileage, then it takes forever for it to get to empty and my mileage is right where it has always been. A tank later and its acting normal.

That thought was in the back of my mind but this is the first time this has happened. I guess I can wait until I hit the gas light or try to fill up and see how much goes in and go from there with the gas gauge.

 

[Biggles]

What about the temperature sensor

My mileage went down a couple of years ago. I could not find anthing wrong.
I did all the clean-up and preventative maintenance things documented in the forum but with no improvement.

I read a thread that commented about engine temperature and faulty sending units. I replaced them and my mileage came back to 15-18 around town 20 on the freeway.

The assumption was that the computer thought the engine was not getting hot enough so the "Choke" was always open.

I read another thread about air in the cooling system causing false temperature reading. I may have been this but I will never know.

The cost of the sending units was cheap.

 

[askingxforxit]

I talked to a coworker last night and he mentioned that it may have been the gas I used at said fill up (post #1) The fact that I went to a different gas station than normal could be my problem. He said that since gas prices are so high that these places can't get rid of 91 octane so they put in the other pumps to get it out of their tanks so it doesn't go bad and they loose money. SO being that the explorer is tuned for 87 and I MAY HAVE gotten 91 with out knowing could be the issue at hand. I'm going to give it a couple more fills at my normal station before I got crazy at the auto parts store and waste time and money.

 

[aldive]

He said that since gas prices are so high that these places can't get rid of 91 octane so they put in the other pumps to get it out of their tanks so it doesn't go bad and they loose money.

Thats nonsense.

SO being that the explorer is tuned for 87 and I MAY HAVE gotten 91 with out knowing could be the issue at hand. I'm going to give it a couple more fills at my normal station before I got crazy at the auto parts store and waste time and money.

You would never notice any difference.

 

[askingxforxit]

Thats nonsense.




You would never notice any difference.

Well it sounded like a possibility. I trust the mans judgment and knowledge, he builds and maintains mini dragsters for his kids and races a 1970 GTO with 1000 HP. I'm still going to wait a couple more fill ups before my wallet starts emptying. Its a mystery to me that I " have no loss in power, performance, and no noises " and the mileage went south. I'm sure it will bring it's self to the surface sooner or later, I just hope later isn't stranded on the freeway far from home

 

[redneck21]

Running 91 in a car made for 87 wont drop make ur MPG go down. Now if u car needs 91 like my prelude and i run 87 it will go down some. Wear did u go to get ur gas B/4 and wear did you get it at when ur millage went down. When i run shell or BP gas i get about 5-7 MPG more then the cheap places that mix 10% ethanol in the gas.

 

[askingxforxit]

Running 91 in a car made for 87 wont drop make ur MPG go down. Now if u car needs 91 like my prelude and i run 87 it will go down some. Wear did u go to get ur gas B/4 and wear did you get it at when ur millage went down. When i run shell or BP gas i get about 5-7 MPG more then the cheap places that mix 10% ethanol in the gas.

I usually fill up at Arco cuz its right by work but the fill up that started it all was at Shell.

 

[askingxforxit]

Well I don't know WTF happened but the mileage issue is "gone" after another fill up I'm getting 400+ to the tank. I hope this isn't a sign of something happening and going to screw me later. I did add some Marvel Mystery Oil in the gas tank to clean things up a bit. The X seems to run a little smoother and accelerates better. I'll probably put some in the crank case on my next oil change.

Many thanks to everyone's input and advice. I love this forum!! Even if I dont have a problem I'll sit here and read other posts and steal ideas:

 

[memhorn]

One thing that sometimes happens to me is that I fill up the gas tank using the small clip to run the gas while I check the oil or tires, and when I slam the hood or jiggle the car the gas pump shuts off even though the tank is not full. Sometimes I double check by pumping more gas, but sometimes I just put the hose away and drive off.

If this happens when the tank is just a couple of gallons away from actually full, the gauge will still appear near the "F" and then my next tank will reflect really bad mileage. In other words, maybe your tank wasn't really full, and the gauge quickly started showing 1/4 tank down with very few miles driven.

 

[memhorn]

Oh yeah, forgot to mention that I have the 3.73 LS and my engine turns at least 2500 rpm at 70 mph. At that speed, I get about 20-21 mpg, all highway.

 

[askingxforxit]

Oh yeah, forgot to mention that I have the 3.73 LS and my engine turns at least 2500 rpm at 70 mph. At that speed, I get about 20-21 mpg, all highway.

Yeah I never thought my RPMs were any lower than that, I'm sure they have always been at 2500 doing 70pmh. When I filled up in post 1, I know the tank was full because the gas pump read 19.x.. GAL and would not go anymore.

I think I got some bad gas or something.....thats bad GASOLINE you dirty minded jokers!!! :