Gas Mileage

[nvrstuk]

Hope I don't bore ya with this....

Bought my '68 in '76 for $2,000 with 49,800 miles on it.

--289, stock 2 bbl. G78x15" tires-then L70x15" tires. LONG trips with mileage checked on road marker posts every 100 miles so mileage was accurate AND written in a notebook in glove box for 25 yrs...
Installed headers, dual exhaust, s m a l l Carter 4 bbl.... mileage stayed the same but a ton more rpm's available to use and much more power.
This netted 18 mpg consistently at 65-70 mph...when speed limit was lowered to 55mph in WA State back in the oil embargo days we consistently got 19-20mph. This is accurate mileage, filled to the top, and odometer right on and written down on the notepad. Wind resistance I found out is the key to mileage... (lifts really hurt mpg).

My Dad's '69 with a 302 that he ordered from the factory, same tires, eventually we put headers, 4 bbl, same setup he could NEVER got over 14.5... he put 286,000 miles on it and kept accurate records...289 is a MUCH thriftier engine.

Back to my '68...
-- when I put 31's on it I lost on average about 1 mpg
-- when I put 33 x9.50's on it and bumped the gear ratio to 4.10's it stayed the same
-- when I lifted 3 1/2" to put 33 x 11.50's under it I dropped down to 14mpg

Put in a 351W slightly built w/cam, headers, 4bbl
I tried 3 spd trannies with OD, I tried several things to get the mileage back above 16-17 and never could...combination of 2" body lift, 3 1/2" suspension lift affected aerodynamics and mpg.

All tires were BFG except for first set of G78 stockers...

--I ran 35's with 4.10's with ZF/203 combo for 12 yrs and consistently got 14.5mpg at 65mpg with my Q'jet. On a "Manly Man" trip with 8 other Broncos we drove our rigs from Seattle to the Rubicon and back, I got the best mileage of all rigs every time with filled up.
2 of them were fuel injected low mileage Exploder motors, 2 converted EFI 5.0 Mustangs, one of these was brand new. My tire height/tire brand, Q-jet setup beat them all.

I got over 14 mpg on the entire trip, including the best mileage on the trail itself. We wrote the mileage, gal purchased and compared mpg at every fill-up and I wrote them all on my dash... (Eric is my witness)!!! : )

I've always tweaked the odometer gears so it would read accurately.

Stroker
--I was running a very healthy 418 first with my trusted Q-jet for 4 yrs and now with SEFI and EDIS on 37's and 4.56 gears on 37x14.5" wide TOYO's for a couple years and lost 2 mpg!!!!

SOLD THE TOYO's... went to GoodYear MTR's and mileage went back up 2 mpg...those TOYO's just don't roll..in fact, on their website they mention that they have high rolling resistance.
--If I run at 55mph I get 14 mpg on long cruises (200+ miles over mountain passes) with the stroker as I have some country roads we cruise on with those speed limits. Freeway speeds knock me down to 12.5 ... both with the Q-jet and the SEFI...no difference at all.

I'm bumping to 40 MTR's, 5.13, D60 front and lowering suspension/body height ...will see...


There's tons more details on things like swapping to different carbs, I went to Holley ProJection in about '92, etc, etc but too much... : )

 

[sykanr0ng]

The OEM's have used air dams on taller trucks for many years, the drag from pushing the air aside at the front must be less than from the turbulence from going over and under and around all the parts of the undercarriage.

I have thought about putting a removable air dam on a lifted classic for use on long highway trips.

 

[landshark99]

My 69 trail rig, engine is a 400 fuel injected with Holley commander MPFI with zf-5, d20 on 35's with 4.56 gears, single exhaust- think 3". I average 13-14 consistently on the highway pulling hills or flats, loaded or light. Altitude doesn't seem to matter but lots of miles above 6000 feet

My 76, 302, GT-40 heads, some kind of comp cam, c-4, d20, 30" tires and 3.5 gears Sanderson headers into single exhaust with cat and muffler, think 2.5" exhaust. Averaged 13-15 on the highway. Recently went up to 31" tires and changed to 4.11 gears, need to see what my mpg's are now

 

[sprdv1]

14 ain't bad really.

 

[deltabronco]

I don't know if it will help, but my grandfather wrote some MPG calculations out on the back of an envelope and kept it in the glove box. He did this in 1977 and the vehicle is a 1976. I still have the envelope. That's about as good as you can get as far as original gas mileage. I can post if it would give some insight. His Bronco is a stock 302 auto.

 

[DirtDonk]

Of course we would like to see that. And an image of the original notes is even better than just a printout of the results too!

Paul

 

[rjrobin2002]

I have c4, 5.0 Mustang EFI, 35s, 4.56 gears and get 14 mpg on my 60mph commute.

 

[rjrobin2002]

My friends Bronco I helped build has 5.0, Explorer EFI and 4r70w, 35s, and 4.10 gears and he got 19mpg on a 55-60 mph 200 mile road trip.

 

[Skiddy]

I have c4, 5.0 Mustang EFI, 35s, 4.56 gears and get 14 mpg on my 60mph commute.

same set up I have, I have no idea on what mileage I get though.
interesting thread with real world experiences

 

[bronconut73]

My friends Bronco I helped build has 5.0, Explorer EFI and 4r70w, 35s, and 4.10 gears and he got 19mpg on a 55-60 mph 200 mile road trip.

Encouraging....

 

[hyghlndr]

Best ever was in a 1972 Bronco powered with a 2003 Mustang V6 3.8L fuel injection with a electronic controlled 4R70W. We were pushing 70-75 mph.

 

[OPCJeff]

When I bought my bronco it had a later model 302 with a 650 holley - 11 mpg

built 347 stroker :

with truck avenger 670 - 11 mpg

with truck avenger 770 - 11 mpg

with quadrajet - 12.5 mpg

with FAST ez efi - 10 mpg

with kind of factory efi - 11 mpg

with 4BT diesel - 24.5 MPG!!!!!!!!!!

 

[Yeller]

I'll play, best ever was 2 tanks at 18 cruising 55-60. on average 12 normal mixed driving, and usually heavy throttle, cuz its FUN. 10 at 80 on the interstate. 37's, 4.56's, 700r4 and the of course everyone's despised 5.3.

 

[nvrstuk]

I think the diesel mileage aspect would be fantastic but personally I just can't handle the noise (at all) but especially when I'm trying to just wander around in the woods looking for wildlife. That's why I sold my early Cummins diesel.

My stroker has tons of power and is too loud when I hammer it (actually trying to stuff 24" long mufflers in) but if I want to cruise or idle I can be quiet...

 

[OPCJeff]

I think the diesel mileage aspect would be fantastic but personally I just can't handle the noise (at all) but especially when I'm trying to just wander around in the woods looking for wildlife. That's why I sold my early Cummins diesel.

My stroke her has tons of power but if I want to idle I can be quiet

I tried so hard to quiet my stroker down and it did not work. The drone in the back was just too much. Now with the diesel its quieter going down the road but yah idle is a joke.

i think the secret for hunting with a diesel is to get dropped off and then have someone else flush the deer your way with rattle trap ;D

 

[nvrstuk]

Yeah, I've built 2 good muffler location options trying to quiet it down while doing my 4 link, seat lowering, ORI, D60 build I am currently doing...

1st option is directly under the front seat/floor area (with heat shields) because now I can fit ABOVE the frame rail Delta Flow 3" dia inlet 50 series (supposed to be NO drone). The 24" will tuck in between my rock skis and the frame and my body mounts that have been moved...very high. With pass side floor raised 2" and the drivers side lowered 2" and with my body lift, they fit perfect ...

OR


between my rear ORI mount behind the axle and the roll cage/frame tie in behind the seat which would normally be directly in front of the stock rear wheel well which I don't have anymore) and the wheelbase is extended...
It would be against the frame rail and s h o u l d have just enough clearance to allow my 40's at full stuff to clear them... won't know till I finish welding up the link mounts again before the weekend...

Anyway, not trying to hi-jack a thread here but quieting this beast down so you can talk while driving down the road is harder than it would seem... EXACT same system with my 351W was perfect for conversation and nice rumble at WOT...add a few hundred horsepower and : )

 

[bronconut73]

Flowmaster Delta 50's have zero drone.
But I can honestly say that they are almost too quiet.
According to Flowmaster these outflow the regular 40's and 44's...but again pretty quiet with the additional chevron that gives it the Delta designation and the additional vacuum/flow....

 

[Yeller]

Yeah, I've built 2 good muffler location options trying to quiet it down while doing my 4 link, seat lowering, ORI, D60 build I am currently doing...

1st option is directly under the front seat/floor area (with heat shields) because now I can fit ABOVE the frame rail Delta Flow 3" dia inlet 50 series (supposed to be NO drone). The 24" will tuck in between my rock skis and the frame and my body mounts that have been moved...very high. With pass side floor raised 2" and the drivers side lowered 2" and with my body lift, they fit perfect ...

OR


between my rear ORI mount behind the axle and the roll cage/frame tie in behind the seat which would normally be directly in front of the stock rear wheel well which I don't have anymore) and the wheelbase is extended...
It would be against the frame rail and s h o u l d have just enough clearance to allow my 40's at full stuff to clear them... won't know till I finish welding up the link mounts again before the weekend...

Anyway, not trying to hi-jack a thread here but quieting this beast down so you can talk while driving down the road is harder than it would seem... EXACT same system with my 351W was perfect for conversation and nice rumble at WOT...add a few hundred horsepower and : )

Time for head sets with intercoms. I love mine and after a road trip I'm not going "what'd you say?" Just from the wind noise, let alone exhaust note

 

[nvrstuk]

Yeah, but they "mess up my hair" is what I hear from my navigator!! : )

 

[nvrstuk]

Flowmaster Delta 50's have zero drone.
But I can honestly say that they are almost too quiet.
According to Flowmaster these outflow the regular 40's and 44's...but again pretty quiet with the additional chevron that gives it the Delta designation and the additional vacuum/flow....

That's the problem I wouldn't mind having but I wouldn't mind a little bit of "attitude" ! I wonder if someone has a recording of a big block with those super 50s?