MPG
Thread Starter
|
Elder User
Joined: Jul 2006
Posts: 804
Likes: 0
From: Maricopa
MPG
So I'm sure it's been discussed on here, but I just want to have one thread maybe that's a compilation, what do you guys know of to get the best mileage(or throw in best power too) out of these engines? just for sake of argument, in a 3 speed auto with a 3.50 rear end.
Cargo Master
Joined: Sep 2007
Posts: 2,095
Likes: 2
From: Wahpeton ND
96, f150, 2WD, M5OD, 3.55 rear. 21 mpg @ 70mph, unloaded, going with a 20mph tailwind.
1985, f150, 4WD, NP435, 3.55 rear. 17 mpg @ 55mph, unloaded, calm day.
1984, f350, 2wd, NP435, 4.56 rear. 14mpg @ 50mph, 4000lbs dirt on flatbed.
1976, f150, 2wd, C4, 3.55 rear. 100,000,000mpg @ 0mph. Any conditions. (Scrapped 3years ago, sat for 10 years.)
1985, f150, 4WD, NP435, 3.55 rear. 17 mpg @ 55mph, unloaded, calm day.
1984, f350, 2wd, NP435, 4.56 rear. 14mpg @ 50mph, 4000lbs dirt on flatbed.
1976, f150, 2wd, C4, 3.55 rear. 100,000,000mpg @ 0mph. Any conditions. (Scrapped 3years ago, sat for 10 years.)
Posting Guru
Joined: May 2007
Posts: 1,208
Likes: 2
From: North Reading Mass
I've had two 300s 2wd 5 speeds. The 94 XL was a reg cab sb with 3.55 gears, 235/15 75 tires and weighed 4000lbs. It would deliver about 18 mpg in the suburbs, 18.5 @ 70+mph and a best of 20 mpg @ 60mph hauling a 400 lb ATV in the bed. When i got that truck I changed the plugs (gapped to .05), put on spirial core wires, replaced the coil with an Accel, and advanced the timing to 12 deg BTDC instead of 10 deg. The gas mileage before was about 15-17mpg before the ignition work.
I also changed out the stock muffler for a cheap turbo muffler and changed the air filter. The difference in the performance of the truck was noticeable and the increase in MPG was a nice bonus.
This truck was still running well when I found my current ride a 95 XLT sc sb with 3.08 gears same tires. With the same mods I get about 1 mpg less than the 94 due to the weight difference. I really don't like the 3.08s with the Mazda 5 speed and will eventually switch to 3.55s or 3.23s or even better a ZF.
regards
rikard
I also changed out the stock muffler for a cheap turbo muffler and changed the air filter. The difference in the performance of the truck was noticeable and the increase in MPG was a nice bonus.
This truck was still running well when I found my current ride a 95 XLT sc sb with 3.08 gears same tires. With the same mods I get about 1 mpg less than the 94 due to the weight difference. I really don't like the 3.08s with the Mazda 5 speed and will eventually switch to 3.55s or 3.23s or even better a ZF.
regards
rikard
Elder User
Joined: Feb 2004
Posts: 830
Likes: 0
From: Indiana
Mine is a 1982 F100 SWB - 300 six, 4 speed trans (4th gear is a O/D), 2.75 rear gears, and 205/70/15 tires. The truck weighs about 3000 lbs. The motor has headers, offenhauser intake and holley 390. I recently checked it and on the interstate and got 18.5. That's 70 mph at 1800 rpm.
I still have some more work to do to it. I have a carb kit to put in and smaller jets. O2 sensor to install so I can tune the carb in.
I also have a unilite distributor to install yet.
Hope to get 20 mpg out of it yet.
Today I was looking at the motor and seen were the head gasket is leaking some antifreeze. That's probably not helping my mileage either.
I still have some more work to do to it. I have a carb kit to put in and smaller jets. O2 sensor to install so I can tune the carb in.
I also have a unilite distributor to install yet.
Hope to get 20 mpg out of it yet.
Today I was looking at the motor and seen were the head gasket is leaking some antifreeze. That's probably not helping my mileage either.
Lead Driver
Joined: Mar 2008
Posts: 7,188
Likes: 384
From: Near Los Angeles
I have a '75 F-350 in F-250 clothing. By that I mean that the registration and emblems all say F-250, but all the suspension and steering are F-350. Nope, it's not a camper special--even more heavy duty.
I recently swapped out a tired old 390 and C6 for a hp 300 with a tricked out C6. My goal was to acheive 50% better milage, but still be able to haul and tow. With the 390 I got 10 mpg rain or shine on the freeway, about 7 around town.
On a recent trip of over 500 miles, 100 of which was through foothills, with varying wind conditions, I averaged 15 mpg at 65 mph. The rear end, which I changed out a few years ago, is a 3.31:1.
With some fine tuning and swapping out the oe single exhaust muffler to dual turbos, and the installation of a Gear Vendor overdrive, I hope to be getting 20 mpg.
I recently swapped out a tired old 390 and C6 for a hp 300 with a tricked out C6. My goal was to acheive 50% better milage, but still be able to haul and tow. With the 390 I got 10 mpg rain or shine on the freeway, about 7 around town.
On a recent trip of over 500 miles, 100 of which was through foothills, with varying wind conditions, I averaged 15 mpg at 65 mph. The rear end, which I changed out a few years ago, is a 3.31:1.
With some fine tuning and swapping out the oe single exhaust muffler to dual turbos, and the installation of a Gear Vendor overdrive, I hope to be getting 20 mpg.
Postmaster
Joined: Dec 2006
Posts: 3,603
Likes: 10
From: Spokane, WA
Do a search. There is at least one thread that is a compilation of probably five pages or more.
Trending Topics
Freshman User
Joined: Sep 2009
Posts: 30
Likes: 1
1m only getting 12 mpg in a 77 300 4sp 4x4 the 4sp doesnt have a overdrive. Im not sure what gears i got ?? My goal is in the 20's
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
3 Best / 3 Worst Parts of Modern Ford Ownership
Brett Foote
10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches
Pouria Savadkouei
Every 2026 Ford Engine Explained
Brett Foote
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
Posting Guru
Joined: Jun 2009
Posts: 1,174
Likes: 0
I got an 86 with mostly the same gear as you and I'm pushing about the same mpg's.
rent trans would help ??
Posting Guru
Joined: Jun 2009
Posts: 1,174
Likes: 0
Something with overdrive would help. I would keep the trans you have though, it'll either be a T-18 or an NP435, both of which are very tough transmissions. You'll be fine as long as you don't do too much freeway driving.
Cargo Master
Joined: Sep 2007
Posts: 2,095
Likes: 2
From: Wahpeton ND
Even with an OD you will only get a 2-3MPG jump.
My opinion on the 300 with an OD is that you should have at least 3.73 gears. 4.10 would be better. 3.55s with a .75 OD ratio is only an effective ratio of 2.67 Way to high to be using a 130 horse engine against a 20 mph headwind.
A 3.73 would .75 OD at 2.80 total ratio
A 3.89 at 2.91
A 4.10 at 3.08
I had an OD with 3.55s. Way too high for going 75 against the wind.
My opinion on the 300 with an OD is that you should have at least 3.73 gears. 4.10 would be better. 3.55s with a .75 OD ratio is only an effective ratio of 2.67 Way to high to be using a 130 horse engine against a 20 mph headwind.
A 3.73 would .75 OD at 2.80 total ratio
A 3.89 at 2.91
A 4.10 at 3.08
I had an OD with 3.55s. Way too high for going 75 against the wind.
