Decrease in Gas Milage Problems

Over the past 4 months, my '99 2.7 taco has been slowly decreasing in gas milage. Over the summer I was averaging around 23. I keep very good care of it, changing oil regularly, align and balance, air filter, the works. It went over 150,000 miles when this decrease began but I cannot figure out what the root cause is. I have ran it with both the deckplate mod on and off, reset the ECU, and have driven it on and off road with no change in milage. I'm now running around 19 MPG no matter if I run it off road all weekend or if I drive 70 on the interstate all week. Could it be a problem with the fuel filter or something that needs to be serviced? Anyone else had this same scenario? As I said, I was getting 24 MPG highway pre-150k and now I'm getting 19 MPG highway post-150k. Please pm me with any ideas.

 

Try this. Seafoam, clean MAF sensor, check/replace plugs, egg under the gas pedal mod.

 

Winter gas will alone will contribute to a 1-3 mpg decrease in efficiency. At least that's what I have experienced.

 

I have the same problem. It seemed to start when it began getting cold out.

 

Actually, cold gas has more tightly compressed air molecules making it denser, which should yield better gas mileage... I'm thinking it's something to do with your Mass Air Flow Sensor or something similar...

 

Thanks for the help. I changed the plugs, wires, and belts less than 25k ago and I live in alabama. Trust me, the weather has been nothing but hot and humid all winter. I'll try the MAS cleaning, but again, no check engine light or any change in driving style to contribute to the problem

 

X2

 

But winter gas blend is different than summer gas and it yields lower mpg. Not only does winter gas evaporate faster than summer (wasted into the air) it also has a lower energy value than summer gas. Which literally equals less bang for your buck.

 

Try filling up at the same gas station every time if you aren't already... I fill up at my local Sam's Club and have gotten consistent mileage for the last 115,000 miles on my Honda Civic... Might just be getting crappy gas from the knock-off stations that buy whatever's next on the line or last off the truck which will have a lot of trash in it...

 

Its not a conspiracy theory or something. Winter gas is a different mixture than summer gas and is written right on the pumps. Maybe in TN the winter isnt "winter" enough to warrant the cold weather blend.

I have got gas at the same Esso (Exxon) for the past 4 years. Only another station if I happen to be out of town.

 

Fuel filter definitely needs to be changed periodically.......I usually do around every 15k with mine. Another thing tho......and even tho it won't throw a check engine light.......your o2 sensors could be causing your mileage drop. If you haven't replaced them ever.....may be a good idea. With them not throwing a cel.......not necessarily bad,but they are nearing the end of their life as far as reading correctly.

 

Winter fuel as opposed to summer fuel definitely makes a difference as well. Also.....ethanol rich fuels(most are nowadays) don't help with mileage either.

 

X4 ^^. I've tracked every tank of gas through 6 vehicles driven by my wife and me over the past 15+ years. Winter gas (here in Colorado) causes about a 15% mileage redux while also killing performance, across the board.

 

Ha Ha this began to happen in late September; I promise its not the winter gas. I have tried different fuel stations and have also tried ethanol vs. pure to no avail. Any way to change or check the fuel filter without taking off the gas tank?

 

lol I wonder if we even get winter gas down here in florida. I swear to god this has been the hottest winter I can ever remember. I just wanted to throw out my 2 cents about the O2 sensors. tacomaman06 is right. I read somewhere that O2 Sensors have an "Average" Life of 50thousand miles. Now I'm sure this is a highly shortened life span because I've had many O2 sensors that have lasted much longer then 50k. But they do tend to fade over time and wont throw a check engine light up until the point of complete Failure.

 

I believe your fuel filter is located under the intake manifold. Pain in the ass to change.....but doable.

 

I am averaging 17.5 miles per gallon after I switched to 265/75/16's. Before that I was getting 20 MPG with the stock 265/70/16's. Is that bad?

 

Wouldn't this mean that more gas is needed to prevent a lean air/fuel ratio...????

lol

 

have you run a fuel system cleaner....something like proguard or the like? some fuels will leave deposits and resins which will present it self as gradually dec power and eroding gas mileage...

Good like

OPI

 

We typically don't get below the teens in the winter although we'll have an occasional single digit night here and there... May be something to that, I've never seen the "Winter Fuel Mix" signs on our gas pumps that I recall...

By the way, we do have stations around here that are known for buying the undesirable gas that is last off the trucks, or whatever is next on the line just to save a buck... And you can tell it if you fill up there... Low price isn't always a good thing to look for on a fill-up...