Hey guys, I'm curious if anyone has any ideas why my MPG have significantly dropped. I was getting approx 19MPG on my 04 4.6L after installing an S&B Air Intake Kit. I consistently got 19MPG for about a year and a half, then all of a sudden I'm sitting at 14 or 15MPG. My driving habits have not changed, and I always fill up at the same gas station. My first thoughts were maybe my O2 sensors have gone bad, but wouldn't that set off my check engine light? I've got 80,000 miles on my truck, and haven't done anything engine related other than the air intake and scheduled maintenance. I am a do-it-myselfer but this is the first vehicle I've owned or worked on newer than a 99. Any advice would be greatly appreciated!! Thanks!

Neal

 

Where are you located at? It's probably just the winter fuels...

 

I guess I should have added that info, I'm in South Georgia. Temps still mid to upper 70s.

 

A lazy O2 sensor will cause that, but I would first check the PCV- a defective one will cause that also. Secondly, if they have gone to winter fuels (even though you might not be in winter yet, that will cause a good drop as well!

 

Man...that's funny this thread got started today!! I just filled up at work and drove my completely normal route home. 43 miles one way. Drove straight from the same gas station I always use to the house just like I always do. Normally with this drive, the gas needle will not move at all. Today, I dropped clear past that "full" white mark. Dropped enough for me to notice.

I wasn't going to say anything until I saw what kind of mileage I got out of the tank, but yea, very wierd. I'm with ya Neal...hope it's the gas like everyone says.

 

If you don't have a programmer I could see it. If you are not throwing a code (check engine light) this is good. My guess is two thigs:
1. New stuff is making your driving a bit more agressive, i don't fault you in the least.
2. The motor is definitely adding more fuel to the mix to compensate for your increased air charge coming in.

I agree that seems pretty steep. If you are not using the same gas station, chances are you are you got some poor gas with that BS ethanol in it.

 

I suffer the same problem and have 78k on my truck. I am thinking the coils may be getting old. I have new ones and will replace them prob this weekend. I will advise of the results.

 

I would change the plugs and fuel filter and see what that does.

 

Im down about 50 km on about 70 liters. I normaly get about 450 km on about 70 liters. Its the cold and winter gas that does it. Its been about 0c to -12c here in Canada the last few weeks.

 

As of January 1, 2004, California completed a transition from methyl tertiary butyl-ether (MTBE) to ethanol as a gasoline oxygenate additive. With most gasoline sold in the state presently containing 5.7 percent ethanol, California is now the largest ethanol fuel market in the United States.

 

First of all, I greatly appreciate all the comments and suggestions! I did change the fuel filter about 6,000 miles ago. I considered changing my coils not too terribly long ago. I heard it's one heck of a pain in the **** to do. Let me know how that goes Screwed Up. Both the procedure and the results

I'm going to try and look into the fuel thing a little further, see if I can find out what they have in their tanks at the station and whatnot. I'll keep in touch!

Neal

 

Checked the PCV last night, the PCV itself wasn't quite connected properly to my intake. Maybe that was the problem! Also, could anyone tell me how much of a vacuum there should be? It didn't seem too strong when I simply put my finger over it, but the longer I left it there the more it sucked, that sound right?

 

Our fuel is higher in ethanol now..............could be the cause..

 

I just changed my cops and I hope that solves the problem. 78k on my 03 Screw.

 

when was the last time the frt o2's were changed