Poor Gas Mileage-Any input appreciated

Greetings, hope everyone is well and having a wonderful holiday. So my taco has recently (last 4-5 months) had a major MPG drop. When I first got the truck 3 years ago i was getting about 17-18 miles to the gallon. Today I get about 11-13 MPG. I have tried 87 Octane and 93 Octane. No difference, had a local mechanic who I trust take a look at it and he didn't find anything wrong with it. I am not versed on trucks (Or any kind of vehicle unfortunately) so I have no idea what the problem could be. I do drive the truck rough sometimes, especially responding to fire calls being a volunteer but my driving habits vary week to week. Recently the fire company has been very quite and I have not been driving rough at all, but my MPG is still horrible. The other weird thing i thought was I have been driving it rough to calls for about 4 years now and just recently my MPG took this major crap.
Any and all suggestions or comments are greatly appreciated.

 

Was about to say since it's getting close to winter, but it's been happening for awhile.

 

Is your check engine light on?

 

U joint, in front of pumpkin. Happened to me and two of my friends recently. Does it make noise or clunking? See if it will take grease. Air filter, plugs, tire pressure, ect.

 

No check engine light is one. Has never come on before. It does sometimes make a clunking sound when shifting from park to drive or visa versa. Didnt know the U-joint could affect MPG though? (Im not truck smart though so) Air filter is a K&N repalcement and was just cleaned about two months ago. Had plugs check by a mechanic said they are okay and look to be around 40,000 miles in. (Truck has 73800 total). I will check tire pressure too. Havent done that. They dont look low to just look at but couldnt hurt. Thanks for all the replies.

Note: I just got gas today. I drove just about 188 miles and the truck took 12.5 gallons of gas. About 15mpg but still bad compared to what ive seen others get on the forum.

 

I'd start with a basic tuneup. If you have been ignoring your rig, then its over-due anyway.

New plugs (NGK or Denso), PCV valve, oil, oil filter.
Also, clean the MAF properly (K&N air filters deposit oil on it).

Grease all drive train zerk fittings.
Set tire pressures to 35 psi.
Get rid of K&N filter, and go back to stock .

 

Bound u joint creates alot of friction.
Good luck

 

There have been several instances of K&N filters getting oil on the Manifold Air sensors (MAP/MAF) and causing reduced mileage. That is one of the main reasons the AFE Pro Dry filters are usually recommended.
You could do a quick clean of the sensor and go back to stock or AFE.

 

Clean throttle body, maf sensor, sea foam.

 

I had a bad injector once that killed mpg.
Pretty easy to diagnose, just take a laser thermometer and point it to each cylinder on the header. If one is running alot cooler than the rest then thats the injector thats hanging open.

 

Awesome. Thanks for all the replies and help. Going to take my truck into the shop this week to have all this performed.
Respectfully,
Randy

 

These are suggestions that MIGHT be your problem, not guaranteed.

Just a warning, if you can't do any of this stuff yourself, it will cost you quite a bit of money to do all of the above, especially the injector and cleaning the throttle body. A good shop should be able to tell if the injector needs replacing.

 

THIS

 

If not mentioned, replace your fuel filter as part of your maintenance. Winter gas may also play a part of your reduced mileage.
Good Luck

 

If it were me, I would remove the K&N filter and buy a Toyota or equivalent paper filter. Not that it's necessarily bad but just to eliminate a variable. Check tire pressure to make sure it's at the recommended pressure, then take a road trip of at least 100 miles, and check your mileage. Try to do it when it isn't bitter cold, keep your speed down, accelerate moderately, take two-lane roads so you can go 55-60, and see if the truck will get its EPA highway rating. It's very hard to assess mileage when you are doing different kinds of driving, and short trips especially in cold weather annihilate your economy. I would do this before spending any money to fix anything. (Obviously if it is due for normal maintenance such as an oil change do that first.)

I have found that most cases of bad mileage are a mixture of driving habits and circumstances such as temperature, weather and trip duration. I've never seen spark plugs or any "tune-up" related things affect mileage one iota on newer vehicles. Not to say it never could, but I never have seen it in a slew of different vehicles I have owned.

 

Thanks to all who posted. Appreciate all the input and suggestions. I took the truck to the body shop last Thursday. They checked the injectors with a laser heat gun, they all were at about 95 degrees Fahrenheit so nothing injector wise was done, tire pressure was set to 35psi, air filter was replaced with a normal paper one, spark plugs were replaced with NGK Iridium plugs, sea foam treatment was done and front end was lubricated. The throttle body was cleaned about 3-4 months ago when I had it in the shop last time, oil is changed regularly and everything else seams to be working fine. Ill keep an eye on my MPG and performance of the truck as well as my driving habits.

 

I'm new to the world of Toyota Tacoma trucks but my other vehicles are BMWs. When my mileage starts to deteriorate (it will normally deteriorate in the winter months slightly because the brain box will enrichen the fuel mixture when cold sets in, making starting and warm-up much easier) my first thought is the lambda sensor (oxygen sensor) so I put the car on the analyzer and it verifys the problem. If the sensor is bad, the engine will revert to full rich mixture, which you will notice by a deterioration in your MPG. As I say, I am very new to Toyota but I believe it does in fact have a Lambda sensor and if your vehicle is approaching high mileage, you might want to look at it. My Ford Ranger sensor lasted about 80K miles.

 

I neglected to mention in my last post that if your EEC reverts to full rich (default setting) due to the Lambda sensor failure, you stand a good chance of taking out the catalytic converter as well. As I pointed out, I am not a Taco expert but I believe most engines of this era have Lambda sensors, EEC boxes, and catalytic converters, and sensors that sense coolant temperature (one of the parameters/inputs to the EEC that adjusts the fuel mixture. Bad coolant sensor will also mean an enriched fuel mixture because the engine still thinks its cold! You might want to research a good Toyota maintenance manual and see what all is in the EEC circuit and proceed from there. From your posts I think you are throwing away an awful lot of good money by troubleshooting your problem with knowing what any of the specifics are. Than can get very expensive.

 

I'm getting shit mileage now too. But, winter gas + lots of idle time + mostly very short (5-10 min) trips = shit mileage lol.

This weekend I was planning on doing most of what was mentioned above and change diff oil also. Most items can be done pretty easily. Search for write ups to save $.