Mpg

[Acknud]

I have a 1969 with a 302. Nothing fancy, oversized tires a little. Last I checked I was getting 9 mpg. Just wondering what other people got.

 

[Godwick]

Sounds about right, but might want to check your carb settings and choke. I get about 11 with a 351 and 32" tires.

Sent from my Pixel 2 using Tapatalk

 

[bmc69]

My '68 with a 3-speed, 3.50 gears and 31" tires got 13-14 with the stock 289 except for an aluminum intake and 500CFM 4V carb, headers and dual exhaust.

The only EB out of the 20 or so I've owned that ever got better than that had a '78 250 6-banger in it..4.10 gears, 3-speed and 35" tires. It hit 15 on occasion.

So..I'd say you could squeeze 2-3 mpg at least out of what you are running. Tailpipe O2 sensors make figuring that out so easy....

 

[Broncobowsher]

Is the speedometer corrected? Oversized tires will not register as much mileage as you actually travel. So that can get you a little more fuel economy, just by fixing the speedometer to record the correct mileage. Aggressive off-road tires naturally have more rolling resistance than a highway tread.

What is your driving pattern like? Does the engine get really warmed up? Not just the water temp, the oil as well, and the transmission, and the rear end. Long drives where everything is warm get way better mileage then cold short trips.

Even then a Bronco typically only gets 12-13 on a good day. Remember the era that these were built in. The Pinto was the economy car of the day, and they were working hard to get it up to a whopping 20 MPG

 

[Acknud]

Is the speedometer corrected? Oversized tires will not register as much mileage as you actually travel. So that can get you a little more fuel economy, just by fixing the speedometer to record the correct mileage. Aggressive off-road tires naturally have more rolling resistance than a highway tread.

What is your driving pattern like? Does the engine get really warmed up? Not just the water temp, the oil as well, and the transmission, and the rear end. Long drives where everything is warm get way better mileage then cold short trips.

I don't take major drives. A good drive for me will be about 80 miles round trip with stops along the way. Most of my driving is within a 15 mile radius. My speedometer is brand new. I haven't even calibrated it yet.

 

[sprdv1]

10ish with Big tires and fuel Inj

It can vary depending on set up and driving style

 

[garberz]

I did a 3800mi. Trip in mine last Sept. I average 13mpg. 35” tires 4.56 gearing, no overdrive. I kept the speed between 60 and 65 for most of the trip.

Mark

 

[AZ73]

I don't take major drives. A good drive for me will be about 80 miles round trip with stops along the way. Most of my driving is within a 15 mile radius. My speedometer is brand new. I haven't even calibrated it yet.

Your speedometer being "new" is irrelevant. It's all about your tire size. Your speedometer/Odometer is geared for the factory tire size. Your factory tire size is 27 inches and does roughly 751 rotations per mile (roughly because there were 2 sizes:26.6 and 27.7). A 33 inch tire will turn 640 rotations per mile. When your odometer says you traveled 1 mile, you've actually traveled 1.1734 miles if you have 33 inch tires. So if you're taking your odometer mileage and dividing by your fuel consumption, you're shorting yourself by 17%. A calculation of 9 mpg is actually 10.5 mpg. Now if you're measuring your distance using a map or GPS, well, you're at 9 mpg. BTW your speedometer is registering 17.34% slower than you're really going if you haven't put a calibrated gear in it. If it says you're going 50, you're actually going 59 if you have 33 inch tires.

The other issue is mileage is better with constant longer distance driving and worse with short trips. Shorter distances use more "choke" before the engine warms up. It's also not as efficient as a long steady drive. My wife works close to home. If she uses the car just to go to work, she averages about 16 MPG. When we use her car to go to California she gets closer to 28 MPG.

To improve as best you can (you're driving a brick), make sure your tires are inflated correctly and use the lowest weight approved oil for your engine. Adjust your carb for 14.6-14.7:1 air fuel ratio. Remove unnecessary weight.

 

[BigToe]

8 to 12, that's just the reality of driving a cinder block.

 

[Pa PITT]

9 Sounds good to me. Back when mine was GAS I only got 4mpg. 302 2bbl.
.............
.... Broncos aren't mileage friendly .. LOL I SWAPED mine over to a Diesel & every one said it'd get 25 to 30 ..
In my BRONCO I get 14.. On the road at about 35 to 40 mph . IN A CAR SHOW CRUISE I got 26 best it's every done.
................
... I'VE about decided Broncos & Gas Mileage shouldn't even be written on the same page.

 

[sprdv1]

................
... I'VE about decided Broncos & Gas Mileage shouldn't even be written on the same page.

LOL, ain't that the truth.. "most cases"

 

[mpboxer]

I get about 10mpg 302, C4, 4.11 gears, 30 inch tires.

 

[Rustytruck]

don't exceed 55 mph as that is the sweet spot. Back in the day 30" tires, 3.5 gearing and emission laden 1974 302 automatic, I could get 15 mpg at 55 mph on a long highway stretch. Faster or slower, mileage went down to 12, all stop and go city down to 10 or so. That was a stock empty Bronco. There was a reason they limited the highway speed back then to 55 mph.

 

[73azbronco]

High single to low double digit is correct especially when its cold outside and not driven long distances. My 2013 jeep gets 15 on short trips and 21 on long trips.

 

[Acknud]

Your speedometer being "new" is irrelevant. It's all about your tire size. Your speedometer/Odometer is geared for the factory tire size.

I'm not sure you understood what I am saying. I don't have an old style odometer/speedometer. I have a new Dakota digital system. I haven't calibrated it for distance and speed yet. It will calibrate taking my tire size into account. I am running 31" tires. My math is rusty so I will never be able to figure it out like you did so I will let the system tell me once I get around to setting it.

 

[Acknud]

8 to 12, that's just the reality of driving a cinder block.

I didn't expect to do any better. Just wanted to compare it to others. I drive it as my regular vehicle and have for the last 14 years. I am used to it. When we really want to go anywhere we take my GFs car!;D

 

[gddyap]

15mpg last year on my way to the Rubicon in my '73. 5.8L SEFI, C4, Cold Duck dual D20s, 4.10 gears, 35s. 3.5 suspension lift, 2 body lift. No top, but with tools and full size spare. I left with a full tank and stopped to get gas on the way. Google maps had me at 90miles from home and I only had to put 6 gallons in. I was cruising at 60mph and most of that 90miles was freeway.
11mpg on my way to WH Roundup in the '66. 2V 289, C4, D20, 3.50 gears. 225/75r15 tires. Stock height, 2 adults, 2 children. Also mostly freeway.
Fuel gauge doesn't work right in the '73 and the odometer doesn't work in the '66. I've always assumed 10mpg and planned accordingly. I'm super conservative with the '73 when offroad because I know I'm getting less than 10mpg.

 

[DirtDonk]

Luckily you don't need to do the math with the Dakota Digital.
But don't just use the tire size on the sidewall as your reference. When your'e reading the instructions I'm pretty sure it will say, but just in case, you need to measure from the vertical distance from the top to the bottom of the tire, with the full weight of the vehicle on the ground, to get the exact size of the tire that the speedometer is going to "see" while you're driving. It's the "rolling diameter" of the tire, not the sidewall number.
For comparison, my BFG 31" tires are actually 29.5" tall on the vehicle.

But even the size might be neither here nor there, if they only want you to push the button when you start and then push it again when you've reached a measured mile.
That's how some of them work, so if that's the case just get your GF's car to drive one mile and make note of the surroundings. Run the same route with the Bronco and you're done.

I like those electronic thingies. Very convenient in some ways.

Paul

 

[blubuckaroo]

I did a mileage test back in the spring of 2015. In preparation I aired the ten ply 275-75-16 tires up to 45 PSI. I had just put the car on a weight loss diet, but for this test I also got rid of all the spare parts, tools, and even ran with the aux tank empty.
My setup was the same as my signature except for the tires.
I drove from Morgan Hill CA to Manteca CA and back. About 180 miles of flat road. I tried not to deviate from 55 MPH while on the road. (hypermiling really pisses off a lot of drivers)
My mileage calculated out to 15.7 MPG.
I think with fuel injection, 16 MPG is doable. I'm still on the fence about adding that upgrade.
At the very least I will be adding a bung so I can connect a temporary AFR meter for better carb tuning. I feel my carbs primaries are probably set up well, but the secondaries run a bit rich.
My normal mileage runs in the 12-13 range and this test just proved out my weight/aerodynamics/tire pressure theories.

 

[broncnaz]

If your overall gearing is not to bad and you do some tuning on the engine you should be able to hit 11-12 no problem. You may want to check your timing and jetting. You may need to play around with the timing to find out what your engine likes best but there are gains to be had and they are nearly free. a well tuned carbed engine will get similar mileage as a EFI but the EFI engine will be a little better in most cases not enough to justify a swap just for mileage purposes.

I havent checked the mileage on my bone stock bronco but my modified one gets 13-14 when all is good and the wind is blowing the right direction and its due a rebuild. Best I remember getting was 16 but that was with narrow tires.