Waiting for more ideas myself. My '06 is getting way worse mpg this season. I DD, 80 miles hwy each day. Last year I would average about 25 mpg (top always down). This season I am getting 20.

I was actually hoping to get better than before, as I put in new plugs (NGK Irridium) and did the valve adjustment, new air filter, right before Spring. But its actually gotten much worse. Nothing else changed.

Hoping for some good ideas here to try next.

 

If you can get it try ethenol free gas.

 

I'm averaging 28-29 mpg with a 200k mile AP1. So something is definitely wrong.

 

Guys, this thread is about helping the OP figure out why his car's MPG suddenly dropped. Posting your own MPG doesn't help.

 

Plugs
Primary O2 sensor
Try pulling any codes and see if anything comes up.
Shitty gas? Try a different gas station on your next fill up.
Finally, I'd try pulling the injectors and inspecting them. Maybe one of them is dumping fuel, and killing your mpg.

 

Dirty air filter also makes it worse. Tire pressure as well. But otherwise unless you're carrying a ton of weight I'm not sure what else it could be. If you have a test pipe or something maybe your o2 sensor or ecu is messing up and running rich. Does it smell like fuel from the exhaust?

 

Since no one has said it yet, our tank level indicators are absolutely worthless imo.

I've been driving to/from columbia sc and greensboro nc twice a week for the past several weeks and I fill up before each of those long streches, and use the same gas stations in both towns.

Temperature, humidty, traffic, etc. have been almost exactly the same for each occasion (I've gotten really lucky weather for those drives, gorgeous top-down weather).


One of the trip I went 62.4 miles before I got the first bar to tick, and then it ticked 1 bar per ~3 miles down 5 bars

The next fill-up I went 12.5 miles before the first bar ticked... lol wtf right?

And then when I get to the last 5 bars it could either be 80 miles to empty, or 5 miles to empty. No joke. So yea, worthless IMO.

The middle ~1/2 of the tank seems to be about where it's most accurate, but that part I don't really care about. Just always reset your trip and know how hard you've been womping it and go by mileage. That's what I do.


Back on topic though, I would just recommend what's already been recommended. But just wanted to let you know about our tanks if you didn't already know.

 

My '06 gas gauge is rather consistent in its in consistency. That is its consistent, just non-linear.

From full down to about 1/3 of a tank its fairly consistent. But the last third ticks by artificially fast for the actual fuel consummed. The last few bars disappear almost right away.

The first bar sometimes varies in how fast it goes away. I just attribute that to variences in how full is full. Not all pumps, even at the same station, shut-off with the same sensitivity.

 

Update:

I pumped the tank back to full and got about 15 miles with 5 bars missing. I went to refill the tank and it took ~3.5 gallons. I've got about 50 miles and I haven't lost a bar yet. I'm thinking the tank isn't consistently filling up all the way.

 

another thing you want to check is your valve adjustment. If you haven't done it and your exhaust valve are tight, then it will do some funky things.

I had the same thing, bad mpg and rich condition. Check and adjusted valve fixed everything so take a look and it get it fixed.