Toyota FJ Cruiser Forum banner

21 - 40 of 82 Posts

·
Registered
Joined
·
107 Posts
My first bet your mileage is so bad is the mud terrain tires. If you switch to AT it will probably go up a good mpg.

You should switch out your rear diff gearing to do the lift/tire size change properly. I've seen charts say a 4.56 rear for 33 inch tires, but the chart was for Jeeps, not FJs.
 

·
Registered
Joined
·
4,701 Posts
First of all, what did you mean when you said you "cleaned your oxygen sensors"?

There are two air-fuel sensors that, along with the MAF sensor, control fuel mixture. There are also two oxygen sensors that monitor catalytic converter efficiency. These sensors have a useful life of 85-100K miles. If your air-fuel sensors are beyond this mileage, they are unavoidably degraded and will not provide accurate data to the engine ECM, and will frequently cause poor fuel economy. If these sensors have not been replaced in the last 100K miles with OEM Denso sensors, they need to be, as accurate mixture control overrides anything else you might try to do to improve MPG.

There is no way to 'clean' either of these sensors, as the critical ceramic electrode is protected inside a perforated metal shell.

Assuming that your fuel-feedback system is functioning properly, 90% of any significant improvement in fuel consumption will come from modifying your driving habits.

As suggested, the fastest and most reliable way to see what's needed is to install some device that will provide real-time feedback on instantaneous fuel consumption. You will be absolutely shocked to see how little throttle, or how slight an increase in RPM, will drive fuel consumption down into the single digit range.

The fastest and least expensive way to get fuel real-time fuel consumption data is with an Bluetooth OBD-2 adapter ($24) that plugs into the OBD connector near your left knee, and the Android app Torque Pro ($5). You can run this on any Android phone, tablet, etc. In addition to instantaneous, long term, and 'trip' fuel consumption, Torque Pro can display hundreds of other important engine and driveline parameters (actual coolant temperature, ignition timing advance, transmission fluid temperature, air-fuel ratio, OBD fault codes, etc.).

Fuel consumption of single VVT-i FJs ('07-'09) can be as good as 18 MPG or higher with a properly maintained engine and conservative driving habits, even with some reasonable mods that add some weight or aero drag.

To achieve this, you need to:
1. Limit highway speed to 65-68 MPH.
2. Start off with minimal throttle opening, and modulate throttle to allow upshifts at around 2,000 RPM.
3. Lots of coasting to stop signs or stoplights, back off the throttle as soon as you see that a stop may be required, even if it is far ahead.
4. Minimal use of brakes: ANY use of brakes (aside from going downhill) is just wasting energy (forward momentum) that you burned fuel to produce.

I have a fairly heavily modified '14 AT (roof-top tent, sliders, heavy 'E' load range tires, skidplates, fridge, recovery gear, on-board air system, etc.) and I can consistently get 19-20 MPG on the highway.

If you install lower gearing or tires substantially larger on diameter than stock you will unavoidably see further reductions in MPG.
 

·
Admin
Joined
·
7,922 Posts
1150676
 

·
Registered
Joined
·
30 Posts
Discussion Starter #26
First of all, what did you mean when you said you "cleaned your oxygen sensors"?

There are two air-fuel sensors that, along with the MAF sensor, control fuel mixture. There are also two oxygen sensors that monitor catalytic converter efficiency. These sensors have a useful life of 85-100K miles. If your sensors are beyond this mileage, they are unavoidably degraded and will not provide accurate data to the engine ECM, and will frequently cause poor fuel economy. If these sensors have not been replaced in the last 100K miles with OEM Denso sensors, they need to be, as accurate mixture control overrides anything else you might try to do to improve MPG.

Assuming that your fuel-feedback system is functioning properly, 90% of any significant improvement in fuel consumption will come from modifying your driving habits.

As suggested, the fastest and most reliable way to see what's needed is to install some device that will provide real-time feedback on instantaneous fuel consumption. You will be absolutely shocked to see how little throttle, or how slight an increase in RPM, will drive fuel consumption down into the single digit range.

The fastest and least expensive way to get fuel real-time fuel consumption data is with an Bluetooth OBD-2 adapter ($24) that plugs into the OBD connector near your left knee, and the Android app Torque Pro ($5). You can run this on any Android phone, tablet, etc. In addition to instantaneous, long term, and 'trip' fuel consumption, Torque Pro can display hundreds of other important engine and driveline parameters (actual coolant temperature, ignition timing advance, transmission fluid temperature, air-fuel ratio, OBD fault codes, etc.).

Fuel consumption of single VVT-i FJs ('07-'09) can be as good as 18 MPG or higher with a properly maintained engine and conservative driving habits, even with some reasonable mods that add some weight or aero drag.

To achieve this, you need to:
1. Limit highway speed to 65-68 MPH.
2. Start off with minimal throttle opening, and modulate throttle to allow upshifts at around 2,000 RPM.
3. Lots of coasting to stop signs or stoplights, back off the throttle as soon as you see that a stop may be required, even if it is far ahead.
4. Minimal use of brakes: ANY use of brakes (aside from going downhill) is just wasting energy (forward momentum) that you burned fuel to produce.

I have a fairly heavily modified '14 AT (roof-top tent, sliders, heavy 'E' load range tires, skidplates, fridge, recovery gear, on-board air system, etc.) and I can consistently get 19-20 MPG on the highway.

If you install lower gearing or tires substantially larger on diameter than stock you will unavoidably see further reductions in MPG.
I deeply appreciate your input and for sure, I'm going to change many things in my driving habits. Thanks for this thorough explanation.
 

·
Admin
Joined
·
7,922 Posts

·
Registered
Joined
·
30 Posts
Ive got a 2007 with 35x12.5x17 km3s, raceline beadlocks, stock gears, and an M1 bumper with a winch. My ultragauge says I’m getting 12.5 avg mp3. I’d be happy if I was getting 14.
 

·
Admin
Joined
·
7,922 Posts
Honestly... I stopped even thinking of gas mileage years ago.

I added an extra gas can on my bumper so I could utilize my whole gas tank and have a plan B if needed.
 

·
Registered
Joined
·
68 Posts
My 08 had a 2.5" lift on 285/70/17at3w load C, and I was 13ish in town and 16-17ish highway. Just part of the brick life
My 14 TTUE has the wrangler asymmetrical MTR tires load E and I feel like im about the same as my 08 lol
 

·
Registered
Joined
·
5 Posts
Hi there,

I hope you can give me a piece of advice to improve my fuel economy in my 07 FJ Cruiser 4WD A/T Base, I'm struggling with its 12-14 mpg each time that I hit the road. I bought this truck for camping trips, long drives, 300, 500, 800, 1000 miles and it's killing me.

I've installed:

A set of 33 in mud terrain tires (I'll replace them for a 33-in Toyo Open Country AT III),
TRD performance air intake,
AFE throttle body spacer,
AFE 3 in exhaust system,
New spark plugs,
Cleaned MAF sensor,
Clean O2 sensors,
Changed CAM position sensor,

Even though it has improved on performance and torque, I still can see the fuel economy is bad, I'd say 14 mpg. I'm planning to regear it, probably with a 3.91 gear set for my 33 in wheelset but I was told that a 4.56 one is what I need.

What would you recommend?
Could be seized calipers. Used to have an 07 4Runner and I was getting 10-12mpg mixed and was BAFFLED at what it could be. Put it up on stands and sure enough I could barely turn the front wheels by hand. Decided to just do rotors/pads/calipers up front and next fuel up I was looking at at WHOPPING 15.5mpg city ;) I think I hit 19 on the hwy once lol.
 

·
Premium Member
Joined
·
13,240 Posts
Zoiks!
 

·
Registered
Joined
·
4,701 Posts
I've learned to use this to measure my instant and average MPG for my old Mustang (when I owned it) and am using it for the FJ now.
But you can get a brand new, well-proven BAFX Bluetooth module AND a used Samsung 7" or 10" Android tablet for the price of the OBD Link unit.

Granted, the BAFX units is Android only, but the premier OBD monitoring app (Torque Pro) is Android only, anyway.
 

·
Registered
Joined
·
30 Posts
Discussion Starter #38
Could be seized calipers. Used to have an 07 4Runner and I was getting 10-12mpg mixed and was BAFFLED at what it could be. Put it up on stands and sure enough I could barely turn the front wheels by hand. Decided to just do rotors/pads/calipers up front and next fuel up I was looking at at WHOPPING 15.5mpg city ;) I think I hit 19 on the hwy once lol.
I didn't think about that. I jacked my FJ up on stands and I could see that wheel don't move totally free. I'll adjust those calipers and pads. Thanks for the hint
 

·
Registered
Joined
·
30 Posts
Discussion Starter #39
I've learned to use this to measure my instant and average MPG for my old Mustang (when I owned it) and am using it for the FJ now.
Currently, I'm using FIXD to monitor engine codes and other things, not sure if this device has those options. But thanks
 

·
Registered
'08 Auto 4WD Black FJC
Joined
·
14 Posts
Driving slower can seriously increase mpg, also do alot more rolling instead of driving and hard breaking. Use the vehicles momentum at stoplights, etc.
55 mph in the truck lane will save you lots of gas, and definitely dont cruise more then 65/70ish on the freeway for long distances if you want to save gas.
 
21 - 40 of 82 Posts
Top