2017 Taco gas mileage falling

Are those the right size tires for your Taco?

 

Not factory, one size up. Truck originally had 17s. Rims came off of FJ Cruiser and are 16s

 

As I know this to be true, sometimes I DO find helpful information via YT. Some things have the "Ring of Truth", others have the smell of BS. The issue of dirty but not yet failed O2 sensors affecting fuel mileage is one of those issues that has neither the ring of truth or the smell of BS. So before doing anything to my vehicle I decided to do more research. While I haven't found any evidence either way that can be considered "definitive" I have come to the conclusion that the best approach at present is to schedule a full diagnostics with the dealership. 15 MPH is just too low. Especially for my driving habits AND driving conditions. The truck hides in the garage during snow storms so I'm not driving around with a ton of weight and aerodynamic drag. The truck is in good condition, tires are wearing down and will likely need to be replaced before next winter, but for now the tires are in good shape. My foot is light. I don't race it around. If I'm not fast enough for someone then they can go around me. Oil changes occur at regular intervals and I use the proper weight of oil. Few days ago during routine maintenance inspection the radiator coolant recovery tank is at proper level, brake fluid is normal and oil level is full. Battery condition is in fairly good condition with a resting voltage of 12V. New batteries tend to rest at 12.6V. Resting at 12V means the battery, 5 years old, may be due for replacing later this year or sometime next year. There are no accessories hanging off my truck to disrupt aerodynamics, though I DO own a lumber rack for carrying long lengths of lumber. But that is only on the truck for those times when needed. Otherwise regular driving - it had a definite affect on fuel mileage. Especially on the highway (lots of wind resistance). So it hangs in the garage over the truck. If/when needed it can be lowered onto the bed of the truck. The truck is kept clean, though in winter times it's harder to do, so there's not a lot of drag due to dirt disrupting what's called "Laminar Flow" where the air at the boundary layer lays still. The smaller that layer the more efficient air flows past. Dirt affects airflow but at a very very small percentage, and can not account for the drop in mileage. Fuel quality is decent or better. I stay away from cheap gas. Saving 17¢ per fill-up and reducing mileage by 20% does not make sense. At least once every three months I throw a fuel additive into the tank to clean the fuel system. Sometimes it's Seafoam, sometimes it's Lucas. Or other additive. Do the same for the wife's Venza and her car gets the same fuel. She's heavy footed with both the gas and brake pedals but she gets 19 MPG average (city and highway). I get on average 23 MPG in her car. And hers is an 09. The Venza is AWD, routine maintenance and tire rotation occur on her car just like on my truck; every 5,000 miles. Give or take maybe 100 miles. But every time the odometer hits a 5K mark (5K, 10K, 15K and so on) it gets its scheduled treatment. Every two months at the longest both vehicles get a checkup. Usually it's done on the first of the month. Fluids and voltages are checked. Tires are looked at. Air pressure is taken. And yes, we run our tires at around 38 PSI. Smaller and lighter vehicles are held between 32 and 34 PSI. Low tire pressure takes a toll on fuel economy, and the local tire shop always puts us up to 40 PSI. But I request a little softer ride, so 36 to 38 is the target.

So, no, I'm not hell bent on pulling the O2 sensors out and cleaning them. I'll wait for the diagnostics to reveal whatever it may.

 

I saw 400 miles DTE on my fill up (19.6 gal) for the first time ever on my 17 (I always saw between 365 and 385). I set the trip ODO and will be able to check on my next fillup

 

I wouldn't jump straight to O2 sensors...
Spark plugs?
Air filter?
MAF and throttle body clean?
Idle habits change ?
ATF?


FWIW, over 7 years, I consistently get 19.5 mpg summer and 18 mpg winter on Shell 91 EO; stock except for 265/75/16 BFG KO2s(53lbs).

 

Thank you all. Today I'm taking it in for diagnostics. All the years I've owned this truck I've never gotten such bad mileage. And literally nothing has changed. I run a Tonau cover but that's it. Factory size tires and rims. Tire pressure is up where it has always been. Yet something has changed. IS changing. Month after month it gets worse.

A few months ago (may have mentioned this already) Toyota replaced the fuel pump on a factory recall. At that time I mentioned the dropping fuel mileage. After replacing the pump they said they reset the fuel mileage indicator. But it has returned back to the same low mileage.

If everything is OK with the truck then it may be the fuel. Who knows how they're trying to make more money out of every gallon they sell?! It could just be stinking gasoline. Well, after today's diagnostics I'll let you all know what the report says. From there - - - ?

 

Yesterday (March 6) Toyota did a full diagnostic inspection on the truck. They found no evidence of anything being out of spec. So it looks like the truck just needs a good hard drive on a couple of good gasoline tankfuls along with some fuel additive to help clean out the system. Hopefully that will help.

Thanks for all the input. Cool website. I've bookmarked this one for later inquires.

 

again,
I think the fix is adjusted expectations. 4x4 V6 owners simply are not getting mid 20s. If you got them in the past, it was just mother nature on your side, blowing wind at your back every direction you went.

 

Five years?

While crossing an open expanse between South Dakota and Cheyenne I had half a tank and range that was clearly good enough to make the trip. Though, unexpected, I ran into a stiff headwind. Maintaining 50MPH was hard, and I watched the "Miles To Empty" gauge go down faster than the miles I was covering. I had to turn back and fill up. After making the 210 mile trip the tank was very close to empty. 17 gallons to cover 210 miles? 12.4 miles per gallon. YIKES! AND I was doing 50 MPH. THAT was Mother Nature. However, while going out on I84 east bound I faced a stiff headwind and mileage was (from memory) around 13 MPG at a sustained 70 MPH.

Historically I've gotten really good mileage for a heavy truck. While in Wisconsin for work I took a rural highway with speed limit of 60. Driving around 64 MPH average I got 23 MPG regularly. It's doable. Flat land, shaded from wind by trees - she'll stretch her legs. Love my Taco. Maybe I'll name her "Rita".

 

try higher octane and resetting learned values via techstream. you could also clean MAF sensor, throttle body, replace air filter, install new spark plugs.

 

Less than 29K miles - - - perhaps the MAF may have something stuck in it. The air filter is fairly new and upon visual inspection is very clean. Spark plugs ? ? ? If after 30K they need replacing then I miss my old 72 Chevy Nova with old breaker point ignition.

I'll consider the MAF.

 

I have a trd OR 4x4 longbed with a gfc camper, c4 hybrid bumper with winch and sliders, and kings all around, with a magnuson supercharger, on 265/75r16s wildpeaks and im getting 17.5mpg averaging 70mph on the freeway. Forgot to add since i do have it boosted i can only run 93 octane.

 

This is from my commute this am to work

 

Honestly, I doubt anything is wrong with the truck. I've tracked every fill up on my truck since new, now around 32k miles, so similar mileage to you. The gas mileage chart in my Fuelio app looks like a seismograph during a major earthquake. The only thing I've learned from that data is that I get between 16-19 MPG during the summer, and 12-15 MPG in the winter. My commutes are short, around 5 miles each way to work and back, and running misc. errands in town, plus maybe 5 minutes per day idling in the winter to warm the truck up. On the highway, I can get 18-19 MPG consistently at 60 MPH without serious hills or wind.

You can track your fill ups over time if you think yours is truly dropping, but in my experience, it's like weighing yourself every day. Unless you can clearly see an overall trend over a long period of time using running averages, you won't obtain any useful information. The only discernible trend is winter vs. summer mileage (in my case).

A few MPG won't make much of an impact on your wallet over time. The difference between 15 MPG vs 20 MPG over 200,000 miles and 20 years of ownership, assuming $3.50/gallon gas is roughly $1.60 per day. Once I did that math for myself, I stopped worrying about MPG, if I was financially concerned about it, I wouldn't have bought a truck. If you're worried about the health and longevity of your engine, it sounds like you are already taking all of the necessary steps to keep it in top shape.

 

Well put.
Many good points (no pun to OP)
In the end; it ain’t broke, don’t fix it.

 

If i drove at 60mph around here id get shot lol

 

Instead of seeking arm chair mechanics advise, get obd2 app and download tacoma service manual. SM has all specifications for most of the sensors and engine "normal" parameters.

 

This has good reviews I did try it in another vehicle don’t know why o2s would be dirty on yours though. My other vehicle was getting a code for o2 or cat issue. The lights not on now but it turned back off by itself before I used this but good for now hopefully. Follow instructions on bottle.

$27 Cataclean Fuel & Exhaust System Cleaner – Pass Emissions Tests – Clear Check Engine Lights – Restores Catalytic Converters, DPF Filters and Cleans Fuel Systems, 16oz (120007)

Cataclean 120007 Complete Engine, Fuel and Exhaust System Cleaner, 473 Milliliter (Packaging May Vary)

I put Techron in mine once a year and fill up with some top tier gas once a year also. Does it help not sure but no issues!
Maybe a tank of top tier gas could help your issue but yours doesn’t sound bad to me.

$22 TECHRON - 266701317 Techron Concentrate Plus Fuel System Cleaner, 32 oz

TECHRON - 266701317 Techron Concentrate Plus Fuel System Cleaner, 32 oz

you may want the fuelly app to track your mpg if you don’t have it.

 

If you have an AT, you might play around with the ECT button. I noticed with my stop and go all city driving, my AT wants to up shift too early.

 

OP you only drive avg of 110 miles a week. Do you do alot of short distance driving? If yes then that explain the low mpg.