2015 getting awful mpg...help!

It "may" retard the timing with a heavy throttle. Most of us aren't flooring it all the time, under normal load the timing is just the same 91 or 87. Still doesn't mean you will see a slight increase in mpg.

 

You must not know how an engine works lol. If it's designed for best performance on 91 it will retard timing the entire time you're driving with 87.

 

The 1GR-FE is the 4.0 L (3956 cc) version, designed for longitudinal mounting in RWD and 4WD pickup applications. It has a 94 mm bore and a stroke of 95 mm. Output is 236 hp (176 kW) at 5200 rpm with 266 lb·ft (361 N·m) of torque at 4000 rpm on 87 octane, and 239 hp (178 kW) at 5200 rpm with 278 lb·ft (377 N·m) at 3700 rpm on 91 octane. This engine features Toyota's VVT-i, variable valve timing system on the intake cam and a compression ratio of 10.0:1.

 

Octane rating won't change mpg.

 

It only retards if the knock sensor tells it to, you must not know how it works. Many here with scangauges which shows the timing have checked into this and found no difference in timing.

 

It will if an engine is having to retard timing to compensate for the octane ratio

 

I just posted the facts for you. I know how it works. The 4.0 is designed to run best on 91 octane, but can run 87.

 

Not if you think it changes the timing all the time.

 

It's not going to change the timing unless it detects pre ign. it does not have intelligence to decide on its own or a method of detection of what’s in the tank. Nor will it advance the timing beyond a fixed point even if you fill it with 100 octane aviation fuel. Too high timing will effect emissions Toyota does not want that or the EPA will be in their face. The manual for my 2011 states 87 or higher meaning as long as you burn 87 all is well there is no statement of higher output with 91. If the figures quoted are correct the 3 HP gain is just about insignificant about one % the weather will have greater effect.

 

All most true 87 has a higher heat value than 91 but it is unlikely the difference can be calculated.
.

 

Bought gas at Fred Meyer today for $1.09/ gal. For 87. With my discount. Costco had it for $1.69.
I usually get 17.5 with 32.4's and stock gears. Got 14 1 time in a 40 mph head wind.

 

It will change timing if it detects knock, which the 4.0 will knock slightly with 87.

 

You really don't know how it works.

 

I'm thinking I do and you don't. 87 octane is what causes the Yota tick. The 4.0 was designed to run 91, but will detune a bit for 87. Countless threads on this.

 

I have a 2015 TRD Off Road 4x4 and it just has plain black mud flaps...

 

Just to update, my 2nd fueling I got 17.8 MPG. (I didn't let it sit in the driveway for 10-15 minutes warming up)

My current fueling is going to be a lot less...I'm between a 3/4 and 1/2 tank and have 128 miles! (I continued not let it idle in the mornings, but I did have it in 4x4 for a few miles on back roads in the snow. That definitely seems to have sucked up more fuel)

 

Then you should question the dealership why. Unless it's like the 2016 and has a 4x4 badge instead?

 

1) Relax relax relax. You start to get an average after a few months. Stop freaking out and over-analyzing every tank.

2) Ignore your 'per 1/4 tank' mileage. That's going to fluctuate wildly and every single truck is going to read different.

3) RELAX! My goodness.

Write down your averages in a notebook. An average / trend is something over a few months, and then you can experiment from there. Right now you don't even have a baseline b/c you're flipping out over every fill-up and time out with 4X4 on.

 

2 things working against you here. Cold weather and using 4wd.

 

Yup, 4WD drops the mileage to 10-12 and lot of that is tire spin finding traction, etc.