I have noticed in the past 2 weeks that my car has been sucking down gas at an alarming rate. I noticed it 2 weeks ago on Saturday, when I filled up at my dad's office and drove to my apartment (55 miles). When I got down to my apartment, I had used over a 1/4 of a tank of gas. I usually barely get past the fill mark. I was only getting 23.8 mpg, when Im usually up around 28/29. I wasn't driving aggressively, wasn't loaded down with stuff, anything. I went home again on this past Saturday, filled up, and same thing. I checked my tire pressure, air filter, all that, everything is the same. I asked my dad if he got in a new load of gas, and he hasn't. There are no check lights or anything seemingly amiss in the car, other than its idling quite rough (thats being checked this weekend at my mechanic). I try to fill up at my dad's every Saturday, and im barely making it through the week now. Any thoughts?

 

My guess would be Oxygen Sensors, they are notorius for causing horrid gas mileage.

 

Interesting, I wouldn't have a check light come on though? I mean the car has almost 64k on it, its time for stuff to start going bad, or am i just being pessimistic?

 

I beleive diffirent cars react diffirentley to a fouled oxygen sensor, you can have your mechanic have a look at them when the car is over there this weekend... All it takes is a glance at them to tell if they need replacing.

I got this from a google search, does this sound a little more like your car?

"The car is a Dodge Caravan, the engine is a Mitsubishi 3.0 liter V-6 with Holley multiport electronic fuel injection. At 100,000 miles(what a coincidence) the car started to run a little badly. A bit of hesitation, and some slight bucking at highway speeds. Full throttle performance was good. Exhaust was a bit smelly, both at idle and when driving. After a day or two of this, the "check engine" light would come on whenever the car had warmed up. I did check, and there was an engine :-) Fuel economy had slipped about 35 percent."

 

The only thing that I can notice is that its idling rough. However, my clutch is starting to go-could it be related?

 

As far as I know, a clutch on its way out wouldnt effect the idle... I could be wrong there, I will let some body else chime in with that...

 

plugs or coils/wires?

Fuel Filter or MAF? O2 sensors, but those may be covered under emissions warranty.

What car is it? If it was a Saturn, I'd say go out and replace your coolant temp sensor...lol.

 

Thats true, it could be a dirty MAF sensor... Do you happen to use a K&N Filter?

 

Its an 04 TSX with 63k on it, AEM intake and Hondata reflash. Nothing else. I drove down to my parents yesterday and back again, and same thing, although the mpg were slightly higher, like 25.5 or so. Highway, I was solidly getting 28.8/29.3, drively normally. This just came on so suddenly, its weird.

 

did you consider if the gas you are putting into the car has an Ethanol mixture to it??? because now that many gas stations added that into the mix, it has greatly decreased gas mileage... i have seen a drastic reduction and try my best to find gas stations that do not use gasahol...

 

It looks like her dad owns the gas station that she fills up from, Her dad would tell her if the gas had any ethanol in it.

 

That was the first thing that I thought of. My dad hasn't had a new gas delivered.