Horrendous Gas Mileage

I have a 2014 Tacoma, 4x4, with the V6 motor. Started out new getting about 22-23 MPG in the summer, and 20 in the winter when new. At this point, it's getting 16.6 when I filled up yesterday, and got about that all summer long. No towing on this last tank, and I only drive 3 miles to work. A tank lasts me at least 2 weeks. I don't let the truck warm up really, or let it idle for any length of time. I get that my daily commute might be affecting the mileage, but this is ridiculous.

So, what has been done; New spark plugs, good ones. 2 new coils, and the rest checked out fine. New air filter. Mass air flow sensor cleaned. My buddy put his scanner on it, a Snap On I think it was, and he found that it seemed to be using 5% more gas on one side. I don't have any more specifics other than that.
But with my fill up yesterday at 16.6 MPG, adding back 5% more fuel would only bring mileage to about 17.5 MPG.

Any thoughts?

 

Has the truck been lifted? Have you changed the tires since you bought it? Added a roof rack? Changed your driving habits? Are your tires low on air? Did you go up a tire size? Is your serpentine belt loose or old?

All things that can affect mileage.

 

Those were absolutely amazing fuel economy numbers. My X-Runner (V-6, 6-speed manual, 4X2 & lowered 2" from the factory) gets similar highway numbers, and ~18 mpg in the city. What you're getting now is probably pretty standard for a 4X4.

I think your buddy was specifically talking about your fuel trims, with one side's LTFT being 5% higher than the other. If I had to venture a guess, either the pre-cat O2 sensor may be weak (going bad) on the higher LTFT side, or your fuel injectors need cleaning.

 

The following thoughts come to mind in no particular order of importance:

- What brand of Spark Plugs did you put in? No need to get fancy here. The OEM Denso plugs are just fine.
- What brand of Ignition Coils did you install? Again, OEM generally work better than aftermarket.
- Have you checked your tire pressures? Colder weather drops tire pressures all by itself.
- Have you checked for a Brake Caliper that may be hung up? Classic way to have your mileage tank. If one is hung up, replace both, but skip the parts store rebuilt / remanufactured junk and either get Toyota OEM Remanufactured (expensive) or new OEM (really expensive) or be prepared to change them every 40,000 miles from now on.

 

Sounds normal to me. I get about ~17 in mixed driving on winter gas and up to 22 in pure highway on summer gas in my stock non-lifted 2009 V6 Tacoma Sport.

 

What spark plugs did you use?

What engine oil and how often do you change it?

Have you checked compression?

Change to upstream air/fuel ratio sensors (not o2 sensors) use denso, and a/f ratio sensors are not exactly the same as o2 sensors.

I'm lifted and always have a bunch of tools in the truck.
Everything runs fine, but i get about 14mpg avg with my setup

 

Anything under +\-10% is considered normal, it just means it’s pulsing fuel longer, the mixture is still the same.

5% actually means it’s lean, not rich.

poor fuel economy in the winter is normal, if you want to try and recoup some, use a block heater.

 

My 15 Prerunner is getting 19. Summer 20-21 with 265/75R16, stock suspension. It seems to run a tab better on 89 octane top tier fuel. Every three months I run a fuel system cleaner. Try cleaning the throttle body and maf sensor. I do that every 30K when I do the plugs.

 

Your short drives aren't helping you, and what is the average speed on your commute?
The best mileage I ever got is on a trip when I drove about 2 1/2 hours each way, 2 lane blacktop, 55 mph speed limit. I drove 55-60 for about 5 hours. I think I got 21 from that tank, but that's ideal.

Look at it this way. If you commute 6 miles per day, that's 30 miles per week. For work only, getting 16.6 mpg, you're using 1.8 gallons of gas.

If you were getting 20 mpg, everyone would be jealous and you'd be using 1.5 gallons of gas. That would be a savings of 0.3 gallons per week, or at $4 per gallon, $1.20 per week (the internet says average gas prices in New Hampshire now are $3.44 per gallon so this is a safe estimate).

IF you replace $100 worth of parts, that's a return on investment of 83 weeks, or 1.6 years.

If something is wrong with the truck, by all means, fix it but don't step over a dollar to pick up a dime. Chances are, your length of commute, and average speeds have something to do with it.

 

No lifts, no bigger tires, no roof racks added. Mass sensor has been cleaned. I'm asking because of the drop in gas mileage. It went from 22 ish in the summer to 17 ish. That seems like a lot. And if it were just work commuting, 3 miles a day, agreed, who cares? BUT, I also somewhat frequently pull a trailer, and drive longer distances, which has to be adding up.

Admittedly, I drive fast, yes. Hard starts and stops, too. But I don't see that whacking my gas mileage by 5 MPG...

NGK Iridium plugs were put in it.

 

During short drive warm up it runs the most rich, its desperately trying to warm up the engine to get the cats operating.

I used to get 13mpg on my 16 tacoma when I lived 5 mins from work. These trucks don't like short drives.

 

This, plus winter gas will do it

 

3 mile commute is your issue. Your A:F mixture is probably closer to 8:1 when truck is cold. I get 20-25% worse fuel economy in the winter. For multiple reasons, these trucks hate cold temps. All your driveline fluids will be of a higher viscosity and therefore add frictional losses. Consider a block heater. Also, short runs don't allow your trucks oil to get hot enough to burn off acids in the oil. It takes about 10 miles to get fully up to temp.
Edit: Also, if you are using the defrost feature, your A/C compressor is kicking in to dry out the air. Pretty much anything that can sap the motors efficiency is in play. 16 MPG is actually pretty good for that length of commute. I personally dislike the A/C coming on for defrost.

 

This. I have a similarly short commute, I'd be thrilled if I got 16mpg in winter, let alone close to 17... hell, I'd be happy with it in summer. I get 14-15 in winter if it's not bitter cold (at which point I am warming it up for 5 or so minutes & mileage goes straight in the shitter)

 

Iridium plugs,nope.

 

I've never gotten 22mpg. 4.0 4x4 stock height dclb. 245 70r 17s

I can get 20 if i drive 300miles on the freeway. if i'm driving around town 16mpg.

Mixed freeway/city is about 17-17.5mpg.

my experience is when a coil pack goes out, the rest are going to soon. might as replace them all, since they have the same amount of firings

they consensus here is replace the iridiums with the normal copper ngks

 

Experiment: go drive a half-tank (or more) of gas at 70+ MPH. Then, return to your normal driving habits- see if the next tank is closer to where you think it should be.

 

Well, it sounds like my truck is in line with most here. I am now doubting my recall of my math results on fuel mileage and the math itself.

How about this; In the summer, I'd get 360 miles to a tank. The light would be on, and I'd put 19 gallons in it. Yesterday, the light was on, with a little over 300 miles and I put 19 gallons in it.

Yes, so putting it that way, I was only getting 18 - something MPG in the summer. I swear to god that doesn't sound right.

At least there doesn't seem to be any real issue with the truck...

 

You might have calculated it on a trip with perfect conditions. On a long drive, about 100 miles, I once got like 21 miles per gallon. Hardly had to slow down and kept it at about 70

 

Sounds pretty good beings you only drive 3 miles at a time, the 4.0 is quite thirsty until it gets up to operating temp. I drive 20 miles to work although on a hilly road and about 18 is as good as I've gotten, if I go a long way on flat road and keep it around 60 I've gotten as high as 21 but mine is a manual which is rated 1-2mpg less than the auto.

If you just drive 3 mi at a time all the time you may just need to take it on a roadtrip and run it, vehicles that do short trips all the time tend to get gunked up from not ever reaching operating temp to burn all the crap out.