Gas Mileage

[Rickb1b]

I kept very good track of my MPG over the course of my build and just thought I'd share some of my results to maybe help out guys looking at combo's.

I started with a totally stock 69 with three speed and 302. I didn't know the condition of the 302 but it had 30 psi oil pressure and 130 psi cylinder compression on all 8. With this I was getting 10 MPG city and 11 highway. In the winter I run 4x4 continuously and got 9 city 10 highway. Highway speed was 65-70.

I then installed a 1 inch body lift and NV3550. Got the exact same MPG nothing changed.

Then I installed 31 in tires and a stock 89 351W, with performer intake and cam, Holley 600; 8.5 compression. Now I get 11 mpg highway 9 mpg city in 4x4.

BTW the speedometer was calibrated with a GPS so it's right on and I spent a week tuning the engine, it's right on also. Although I could speed the timing up a little. It's at 35 total but doesn't get there until around 3,500 RPM.

I hear lots of guys getting better than this, I'd love to know how they are doing it.

BTW I love this as a street combo: 351W, performer cam/intake, Holley 600, 31 tires, 4.11 gears, nv3550.

 

[blubuckaroo]

The easiest way to get better gas mileage is to lie about it.
It's not the engine speed but the wind resistance that's killing your mileage. Our car is set up very similar to yours and I've done some testing on my own. Ours gets around 17 at 55 MPH and 12 at 70 MPH. Your overdrive may also be keeping your engine out of its proper torque RPM. Your best mileage will happen when you travel at the engine's maximum torque RPM. Most of the factory Bronco engines had a maximum torque somewhere between 1800 and 2000 RPM and that's where you will get your best mileage as long as you're not traveling over 55.

 

[Deano]

Or go back to a I 6 then you can get 19-21 at 55mph but don't expect to go any faster than that. That's all it's got capton.

 

[u10072]

Oil is at $46 a barrel-- who cares what the mileage is lol!! It is funny when guys talk about fuel mileage that's better than an 89-93 mustang-- with a 89-93 mustang engine in it-- it like really?? I guess the laws if physics don't apply to your bronco lol!!

 

[904Bronco]

When you own a Bronco, mileage is not something you worry about... ;D

 

[BluebroncoNC]

If you have to ask....

Nissan Leaf forum ---------> that way.

 

[broncnaz]

A lot of 302s had maximum torque closer to 2600 RPM later 70's had it down around 2200. Now early 351's tend to be down around the 1800 RPM range. late 80's well max torque is around 2800 RPM. Not sure where max torque is with a performer cam but it should be fairly close to that 2800. That coupled with your gearing/tire size and at 75mph you should be running about 2700 rpm.
351's are not really mileage masters but you should have been able to pick up a little with its better lowend torque. But then again maybe your gearing and tire size are causing the RPMs to be a little to high for the 351's liking. As your most likely cruising at its torque peak while its not working hard its normaly better to run under the curve even tho the curve is fairly flat but lower RPM's means less throttle aand less gas needed.
I would get the timing all in by 3000 and double check the jetting you may even need to play around with it a little more to see if you get any changes. Things that look right on may not be.
Its all a fine balancing act. If you like your tire size then 3.50 gears may be the answer. Or step up to say 33in tires see if that helps/hurts anything. You really have to to consider what a lot of guys are running for RPM's on the hiway that have similar engines.

 

[Viperwolf1]

Oil is at $46 a barrel-- who cares what the mileage is lol!! It is funny when guys talk about fuel mileage that's better than an 89-93 mustang-- with a 89-93 mustang engine in it-- it like really?? I guess the laws if physics don't apply to your bronco lol!!

I can get 16 on the highway with mine. I would think the mustang my engine came from would do better than that. The engine has been modified some though.

 

[stout22]

Back in the day I had a bone stock uncut 73 Ranger with a 302 and auto that got 17mpg on highway driving 55. It did have a lot of rust so maybe it was lighter than a solid Bronco%)

 

[blubuckaroo]

The fuel economy on ours actually improved when we got rid of the wide floatation type tires and went to narrower truck type tires. The ride and handling was improved also.
Weight and vehicle lifts are also factors that affect your mileage.

 

[Outlaw Bronco]

Stock 3 speed, gears, tire size. 347 cid gets 15-16 mpg @ 55 mph, 2600 rpm.

Pretty happy with it, but i am sure my plans of 35's, 4.56 gears will kill the heck out of it.

 

[wepuckett]

Hey I am used to trucks and not the best gas mileage usually always under 20 even in my other vehicles so if I get at least double digits in the bronco I am more then happy.

 

[Rickb1b]

Maybe I'll do an experiment. I usually drive the highway between 65-70, I would be curious what I would get at 55. Although "I cant drive 55".

 

[jw0747]

The easiest way to get better gas mileage is to lie about it.

No kidding. If you tell people you're getting 15 mpg or better in an EB how do we know it's true?

Back in the 70s during the embargo and soon after we had guys telling us they were getting 20-25 mpg in their F-150 size Ford pickups. You could actually stare at them and see their noses growing outward.

Don't ever complain about gas mileage in an Early Bronco. For comparison I had a new 1972 Ford Maverick w/ 302 + C4 and it never got any better than 12.5 mpg in town or on a long trip.

 

[Rickb1b]

Actually, I used to get 15 mpg, but then I calibrated my speedometer to the GPS.

 

[smokinjoe]

My 70 Stang w/ a 302 30 over gets over 20 cruising around 68 mph or so, but it's also got a 3.0 gear ratio and a T5 w/ overdrive

The Bronco??? Not even gonna try, jus' make sure the needle stays above 'E'

 

[bronconut73]

I am doing good at 11 mpg....

You guys getting 15+ are really doing good.
Hard to imagine an eb getting much over 17 mpg.

 

[sriha]

Hard to say what I get but calculating off of distance that I drove and how much I put in afterwards I think I am in the upper teens. I went about 100 miles plus a weekend of wheeling and only put in 5 gals when I returned. Average road speed was 60mph. I have a 302 with a 2 barrel carb, axles are 3.50, I have 34" swamper LTBs and 2.5" lift with a 1" body lift. I think my truck is relatively light but probably still 4500lbs. I did hit 70mph at one time but that was pretty scary with touchy steering and tires that probably should not see that speed.

 

[Rox Crusher]

I don't "worry" about mileage but it is interesting to track

Mine has been getting worse mileage lately but the reduced fuel pricing more than makes up for it.

 

[WheelHorse]

Have you installed a wide band on it to see where your AFR is going down the road?