35s and 3.73: What's Your MPG?

[Ninjak]

I was going to upgrade to 37s when I wear mine out, but the hit in mpg is big.

I would probably do better on highway, but most of my driving is city.

I dont even bother on eco mode. I do not get any improvement in MPG, just feels more sluggish. Normal mode or sport mode is better, especially on Highways.

Yes. I need to do the Forscan mod to get Sport Mode. I am a Badlands, so no sport mode from factory.

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[KillerPenz]

I dont even bother on eco mode. I do not get any improvement in MPG, just feels more sluggish. Normal mode or sport mode is better, especially on Highways.

Honestly, I didn't feel much difference in Eco mode. I know when I switched, the mileage did go up by 3/10ths or 4/10ths. And if I need to pass, the power is there.

Personally, most of all this is probably in our heads anyways.

 

[KillerPenz]

Why do you people with a different axle ratio then what the op is asking keep answering his question?

It's called boredom. Or maybe trying to give OP an idea what we get, and when someone does answer or come close to what he has, he can then make an educated guess.

Why do you ask the question above rather than answer his question? (keep in mind I didn't look at rest of this thread to see if you actually did or not.)

 

[akturbo]

Why do you people with a different axle ratio then what the op is asking keep answering his question?

Well, at least they're giving info for Broncos! "I don't have a Bronco but my Tesla gets 107MPG".

 

[JT58Bronc]

It's called boredom. Or maybe trying to give OP an idea what we get, and when someone does answer or come close to what he has, he can then make an educated guess.

Why do you ask the question above rather than answer his question? (keep in mind I didn't look at rest of this thread to see if you actually did or not.)

I drive in Eco.... and a light foot... until the guy in front of me pisses me off and I go around him. And still topping out around 18.2. How the hell are you getting 22? Do you only drive on highways and downhill all the time? I must be missing something.

I just drive normal, normal mode. Coast to a stop when I can and let the engine shut off with start stop at the long lights. Roads are flat and straight with warm temps (Fl) and I drive with windows down and AC off. Some highway I drive no more than 70. I have a lightweight package though- Base Sasquatch 2 door no mods or accessories. I purposely wanted the most light weight Bronco with biggest engine. It moves too, I never have to press on it hard. When I rarely do it gets up to 85 real fast. I use 87 octane too. Lightweight vehicle, big engine low RPM equal MPG. I got over 30 MPG in my C6 Corvette.

 

[indio22]

I bought a vanilla OBX a few weeks ago thinking I could throw 35s on after yanking the crash bars and not get destroyed on by mileage. After educating myself on ratios, I kinda regret not going squatch. I don't mind a hit it mileage, but I also don't wanna get 11 mpg highway. A regear is off the table for now.

Can anyone with 3.73 and 35s chime in with your rough mpg? I have a 2.7, FWIW.

Cue the "you bought a bronco, who cares about mpgs?" crowd...

Back in the old days of 3 speed non-OD or 4 speed OD automatic transmissions, the diff gears were more important. And you could end up with a final drive out of whack. Meaning way too low rpm.

Not that diff gears don't also matter today, but now you have the 10 speed automatic, with several OD gears. That could change the picture, if the Bronco auto is able to smartly select the best OD gear for your larger tires.

I don't know for sure, but maybe someone with your setup could comment, does the auto maybe stay in 8th or 9th gear more on the highway, to account for the larger diameter tires? If it has that capability, then you could be ok even with the larger diameter tires (meaning lesser mpg and power penalty).

 

[Johnny Rebel]

2 door Big Bend non-squatch, 2.3L, 3.73’s, King 2.5’s, 37x12.5 BFG KM3’s, Ford Performance tune.

I run in Sport mode at all times. Highway mileage @80 mph avg speed is consistently 15-16 mpg. Mileage is slightly worse in Normal mode and significantly worse in Eco mode.

 

[IINCEPTIONII]

Back in the old days of 3 speed non-OD or 4 speed OD automatic transmissions, the diff gears were more important. And you could end up with a final drive out of whack. Meaning way too low rpm.

Not that diff gears don't also matter today, but now you have the 10 speed automatic, with several OD gears. That could change the picture, if the Bronco auto is able to smartly select the best OD gear for your larger tires.

I don't know for sure, but maybe someone with your setup could comment, does the auto maybe stay in 8th or 9th gear more on the highway, to account for the larger diameter tires? If it has that capability, then you could be ok even with the larger diameter tires (meaning lesser mpg and power penalty).

That's really what I'm hoping - that the tranny will know where to sit based on how hard it's working. I've seen a few reports of people using sport mode to lock out 9th and 10th, and it seems like their results have been good.

2 door Big Bend non-squatch, 2.3L, 3.73’s, King 2.5’s, 37x12.5 BFG KM3’s, Ford Performance tune.

I run in Sport mode at all times. Highway mileage @80 mph avg speed is consistently 15-16 mpg. Mileage is slightly worse in Normal mode and significantly worse in Eco mode.

Now you're talkin'. What a great looking ride, and thanks for the detailed info. Did you recalibrate your speedo as well?

 

[Johnny Rebel]

That's really what I'm hoping - that the tranny will know where to sit based on how hard it's working. I've seen a few reports of people using sport mode to lock out 9th and 10th, and it seems like their results have been good.



Now you're talkin'. What a great looking ride, and thanks for the detailed info. Did you recalibrate your speedo as well?

Thanks! I did the speedo calibration with the Ford Performance tuner.

Sport mode does lock 9th & 10th gears out, so it runs in 8th. Good temp solution instead of re-gearing for now. I’ll eventually do the full Spicer axle upgrades when I can save up enough $$$ to buy the parts.

 

[mattymik]

I have 3.73 gears and 295/70/18 (34.3”)

15.5 is the best I can manage on my suburban driving, and I’m a pretty conservative driver.

However I’ve not re-calibrated with FORSCAN. This ought to be ~10% higher (16.5-17) if you properly factor the new tire size. I don’t see people addressing that point

 

[Quitefrankly]

17 with tune premium and gear on the truck. If you get 20 mpg on this engine your legit barely alive.

 

[Sadams27]

I bought a vanilla OBX a few weeks ago thinking I could throw 35s on after yanking the crash bars and not get destroyed on by mileage. After educating myself on ratios, I kinda regret not going squatch. I don't mind a hit it mileage, but I also don't wanna get 11 mpg highway. A regear is off the table for now.

Can anyone with 3.73 and 35s chime in with your rough mpg? I have a 2.7, FWIW.

Cue the "you bought a bronco, who cares about mpgs?" crowd...

I have the exact same set up. OBX non SAS on 35s, 3.73. I average 16.9 MPG. Drive mainly in Sport mode.

 

[Big Jim]

It's called boredom. Or maybe trying to give OP an idea what we get, and when someone does answer or come close to what he has, he can then make an educated guess.

Why do you ask the question above rather than answer his question? (keep in mind I didn't look at rest of this thread to see if you actually did or not.)

Cuz i dont have the gear ratio he is specically asking for, duh

 

[Big Jim]

I had an old cj7 back in the day. 4” lift, 36” rubber, 360 with headers exiting out the side with 3” cherry bombs. Never really cared about the miles per gallon. Just so you know

 

[refade1]

2 door Big Bend non-squatch, 2.3L, 3.73’s, King 2.5’s, 37x12.5 BFG KM3’s, Ford Performance tune.

I run in Sport mode at all times. Highway mileage @80 mph avg speed is consistently 15-16 mpg. Mileage is slightly worse in Normal mode and significantly worse in Eco mode.

Have you taken it off road? Any issues with steering? Nice bronco!

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