Struggling with 12 mpg

Something ain't right. My 07 is basically the same truck, same tire size, same engine and I live in NW GA. I don't do much true city driving. My everyday driving is rural 2 lane and small town traffic and I get 15-16 mpg. On the road 19-20 mpg. My 2014 F-150 Supercrew 4X4 is only about 1 mpg worse than my Tacoma.

Winter gas makes no more than 1 mpg difference. That tire size isn't enough bigger than stock to matter. If most of your driving is in a large city like Atlanta then 12 makes sense, but you should be in the upper teens on the highway. One simple thing that can make a big difference is the air pressure in the tires. I keep mine a little on the hard side running in the upper 30 psi range. About 38-40 psi. If you're below 35 psi it will ride better, but you pay for it with more fuel.

 

There's no way, I only lost about 0.5 mpg when we switched recently.

I never get less that 20 mpg , stock tires but lifted.
There is no reason a taco should only get 12 unless it's slap covered in steel armor and has mega tires.

 

I've never hit 20, most of my highway driving is in the mountains.

 

Yeah, I dont really buy into the whole winter gas theory that much either..

 

It probably depends on where you live but I've documented losing around 1.5 to 2 mpg with just about every vehicle I've owned when the winter gas hits. But the OP's 12 mpg is extremely low if he isn't lifted with bigger tires and extra weight. It looks like I'm going to average around 14 to 14.5 mpg this winter with it being city/around town driving so my Tacoma is almost as bad as my old Silverado was. Highway mixed in will get me up to 16 mpg and I'm lifted 3" on 33" tires with the 2.7 and automatic. The OP may need to get a Cangauge or Ultragauge to see what the computer is showing. He should be getting at least 14-15 mpg city and probably more mixed.

 

My truck has never hit 215*. I’m usually around the 180-190 mark unless hauling or towing on the interstate.

After a coolant flush my temp hasn’t gotten above 186.

 

One more suggestion... go for a drive, a freeway drive (limited stops), after filling up with good gasoline (not premium, just a good name brand like Chevron or Shell or whatever your state has like that). With tires properly inflated (did you do the chalk test?) and limited gear along for weight consideration, drive out 100 miles and back... 200 highway miles, should take you 4 hours or less (keep it at 65 mph or less)... then fill the tank and do the math. Hopefully, you will need only 11-12 gallons giving you close to a 17-18 mpg range... or maybe you will get better? If 10 gallons fills the tank then you got 20 mpg! I have only done that a couple times in my truck, which is like yours in weight... 4WD DC Automatic V-6. Remember, the taller 75 series tires will slow the odometer, so add 4% to the miles recorder to be accurate with how far you traveled.

 

Coolant temp is a big factor but you'd expect to see a p0128 if the coolant wasn't reaching/staying at operating temp. OP said he hasn't seen any cel or codes..

 

Couldn't it just be the colder weather though? (Theoretically) the engine will have to burn more gas to stay nice and toasty when it gets cold

 

I'm fairly certain (at least in Southern CA) that we don't get winter fuel...stays the same year round. Doesn't get cold enough here for long enough to justify it

 

The losses of heat through the engine bay into the surrounding atmosphere would be pretty negligible, even on a really cold day. At most, the thermostat would just cycle less.

 

My mileage is around 13 mpg in city and 17 on hwy. I'm running 265/75's and 140 lb sliders. After getting these my mileage dipped a couple mpg's. What affects me more than anything is the way I drive. I run a scangauge and I'm always trying to get the best mileage on my drives. If I don't watch, my mileage can dip quite a bit. What doesn't help either is I drive down in elevation to work and back up at the end. On the hwy it's up the mountain, then back down. Sure I get to coast going back down, but it never makes up for the shitty uphill mileage. Perhaps it's as simple as your hilly terrain and the way you drive.
The V6 Tacomas typically don't get the best mileage.

 

Oh, but we do have a summer blend so when I say "winter fuel" it means normal gasoline and not the stuff we get in summer that drops our mileage. Now, if we could only get pure gasoline without the ethanol dilution!!! I love driving in Mexico as the gasoline there is real gasoline, no ethanol added! My mileage goes up in Mexico, even when I have a load of camping gear!

https://www.popularmechanics.com/ca...blend-gasoline-whats-the-difference-13747431/

https://www.eia.gov/todayinenergy/detail.php?id=11031

"Special fuel formulas

California's tough environmental rules mandate that gasoline sold within the state be produced according to strict formulas that reduce pollution. But the gas is more expensive and difficult to produce than dirtier fuel sold elsewhere. Few refineries outside the state are equipped to produce it. What's more, the state gasoline formula changes twice a year, from a winter recipe to a summer blend designed to retard evaporation during warm-weather months. The summer blend is even more expensive and trickier to make, increasing the chance of refinery mishaps. In addition, refiners try to use up inventories of one type of fuel before the switch to the other type, increasing the risk of price volatility."

The above quote is from: https://www.latimes.com/business/la-fi-gasoline-manipulation-infobox-20150706-story.html

 

True, but if it's really cold out, that period of time before it gets fully warmed up is going to be a pretty rich mixture.

 

https://www.discounttire.com/learn/tire-size-calculator

 

Have you verified that the Oxygen sensors are switching from lean to rich ? Do you know for certain that the PCM is in control of the fuel delivery? Only a scan tool can help you determine this. Also, have any of the Oxygen sensors been eliminated or modified with anti fouling spark plug extenders? My guess is someone had to have changed something. Engine management system are extremely reliable and responsive providing excellent fuel mileage, drive ability and low exhaust emissions. It’s when the home mechanic messes with this system that causes havoc. Seen everything imaginable done by my students because they believe they are an Automotive genius, engineer extrodinare. lol

 

I am still getting 12mpg.

I have Installed a volant CAI, replaced the air filter, did a fuel trim test, and tried Premium fuel.

fuel trim test. first 2 pictures >idle<


fuel trim test. second 2 pictures >2,500rpm<

 

my 06 gets around 14, kinda just what happens as the truck ages.

 

While our V6 isn't known for great fuel economy,I believe really poor economy is generally due driving style. This assumes the truck is running correctly, is stock ,and not heavily loaded or towing. I often see that driving style here. I was behind a guy recently who blipped the throttle(with his loud exhaust) constantly the whole time I was following. I'm not even sure he was aware of it. Long idling and warm up time is 0 mpg. Jack rabbit starts and slamming on the brakes at lights all deteriorate already poor economy. Some people just don't care about their gas expenses I guess. Those that do already know what to do. Winter fuel, here anyway, is a known milage killer also. Not all areas of the country use that as far as I know.

What is the term used on Tirerack? "Spirited Driving"... probably equals low fuel milage.

 

Rear cats are not monitored.