What would you do first?
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Laughing Gas
Joined: Aug 2010
Posts: 982
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From: Northern Kentucky
What would you do first?
I am interested in making 2 changes to my truck to try to improve my MPG some, but I know better than to make both changes at once. I have an Edelbrock AVS carb and DS2 ignition. I would like to lean out the carb jetting a bit and also try a bit more ignition advance. Currently jetted 1 stage lean in cruise mode and 10 degrees BTDC on ignition. I want to try 2 stages lean in cruise mode and also try 12 deg. BTDC. But which change to make first? What say you gentlemen?
FTE Legend
Joined: Nov 2015
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From: Angier, NC
First do you have a AFR gauge installed?
If not get one as that will be the only way to know if running to lean or not.
Guess you could look at plugs but that can get tricky.
So with that I would do the timing first but I dont know if bumping it up will do much for MPG?
You may want to do a re-curve of the dist. to get the MPG up.
BTW what is it you are working on and what is the MPG now?
You may be at the top of MPG now and nothing you do will help.
Dave ----
If not get one as that will be the only way to know if running to lean or not.
Guess you could look at plugs but that can get tricky.
So with that I would do the timing first but I dont know if bumping it up will do much for MPG?
You may want to do a re-curve of the dist. to get the MPG up.
BTW what is it you are working on and what is the MPG now?
You may be at the top of MPG now and nothing you do will help.
Dave ----
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Laughing Gas
Joined: Aug 2010
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From: Northern Kentucky
No I don't have an AFR meter. The engine description is in my signature but it is a 351W, internally stock but with shorty headers, Edelbrock carb and intake, and recurved DS2 distributor. It is in an F250 4x4 with C-6 trans and 3.55 gearing. My current mileage in mixed driving is 10.5 MPG. I was hoping to move it up to around 12 MPG or so at least. Current performance is pretty decent on acceleration with no pinging so I thought I may be able to lean it out a bit to pick up a little more MPG.
FTE Legend
Joined: Nov 2015
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From: Angier, NC
Ok on the spec of the truck as I thought I seen something about manual trans and then C6 
You can try bumping the timing up to see what it dose but with out the AFR meter it will be hard to tell just what the motor is running for ratio and if would be safe to lean it out more.
I have a gauge on my 300 six and I have been thinking of leaning it out some but fear of going to lean asI am running between 13.5 to 14.5 and avg. 15 MPG with mix driving. Thing is mine is a 4x2 so less air goes under the truck to kill MPG and being a SB also weighs less.
I also run a manual trans, an over drive unit and a 2.75 rear gear. The motor sweet spot is about 1800 RPM and being I can split gears I can keep in in the sweet spot.
Dave ----
You can try bumping the timing up to see what it dose but with out the AFR meter it will be hard to tell just what the motor is running for ratio and if would be safe to lean it out more.
I have a gauge on my 300 six and I have been thinking of leaning it out some but fear of going to lean asI am running between 13.5 to 14.5 and avg. 15 MPG with mix driving. Thing is mine is a 4x2 so less air goes under the truck to kill MPG and being a SB also weighs less.
I also run a manual trans, an over drive unit and a 2.75 rear gear. The motor sweet spot is about 1800 RPM and being I can split gears I can keep in in the sweet spot.
Dave ----
Lead Driver
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From: Tolland, CT
A different view, if you bought a car that gets great mpg for your daily use, would the money you saved by not having to buy a gallon of gas every 14 miles, help pay for the car payment. Plus give you a safer vehicle to drive...
Seems there have been a few threads here recently, about wanting better mpg from a 35+ y/o truck.
We have a 2023 Nissan Rouge, that gets 35+mpg pretty easily.
Seems there have been a few threads here recently, about wanting better mpg from a 35+ y/o truck.
We have a 2023 Nissan Rouge, that gets 35+mpg pretty easily.
FTE Legend
Joined: Nov 2015
Posts: 30,828
Likes: 4,094
From: Angier, NC
A different view, if you bought a car that gets great mpg for your daily use, would the money you saved by not having to buy a gallon of gas every 14 miles, help pay for the car payment. Plus give you a safer vehicle to drive...
Seems there have been a few threads here recently, about wanting better mpg from a 35+ y/o truck.
We have a 2023 Nissan Rouge, that gets 35+mpg pretty easily.
Seems there have been a few threads here recently, about wanting better mpg from a 35+ y/o truck.
We have a 2023 Nissan Rouge, that gets 35+mpg pretty easily.
But there is nothing as cool as driving our trucks even with not so great MPG.
My 02 Durango gets the same 15 MPG avg as my pick up and I hate driving my wife's 2013 Subaru.
So I drive the pick up when ever I can.
But I think he can do a little work to the truck to get better than 7 MPG.
Just need a little more info on the truck to point him in the right direction.
As a start bump the tire PSI up a little so it rolls easier.
On tires, lighter tires & wheels also helps. You running factory stock size?
Could replace the front, rear and transfer case oils with synthetic oil.
On a 4x4 I dont know how much this will help but on a 4x2 truck the air dam that bolts on to the bottom of the bumpers on newer trucks will also help on outs as someone has given it a try.
There was a 80 - 86 model that was for fuel MPG that had this air dam and IIRC has a Ford part number.
I have been thinking of fitting one on my truck just to see what it would do as I dont think it could hurt.
It is all about keeping air from going under the truck causing drag.
Dave ----
Lead Driver
Joined: Jun 2013
Posts: 5,641
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From: Tolland, CT
Interesting about the 13' Subaru. My main DD is an 18' Outback 3.6R. It's a pretty ride for its price range, checks a lot of boxes. Also have two 4th Gen Legacy GT's. They are both on a custom tune and will get 26+ mpg on the highway.
I recall back in April 1982 when we got an 82' Honda Civic FE 41-46mpg, and thinking with the money we save in gas, went a long way towards the car payment. She had a 71 Dodge Demon 6 cylinder, I had a 1970 340 Duster with a built motor. There was one time in Aug 83, heading east on I90 in NY state, the car got over 54mpg, had a good tailwind that day.
Back on track, would thinner tires help the OP with better mpg ? But here we go, spending hundreds of dollars to save a few.
I think most of us have learned just to suck it and drive the truck... but then again. I shouldn't talk about mpg and the truck when mine gets less than 5000 miles in 12 years or more. My truck cost me more to keep it then the use I get out of it...but when I need a truck, I have one.
I recall back in April 1982 when we got an 82' Honda Civic FE 41-46mpg, and thinking with the money we save in gas, went a long way towards the car payment. She had a 71 Dodge Demon 6 cylinder, I had a 1970 340 Duster with a built motor. There was one time in Aug 83, heading east on I90 in NY state, the car got over 54mpg, had a good tailwind that day.
Back on track, would thinner tires help the OP with better mpg ? But here we go, spending hundreds of dollars to save a few.
I think most of us have learned just to suck it and drive the truck... but then again. I shouldn't talk about mpg and the truck when mine gets less than 5000 miles in 12 years or more. My truck cost me more to keep it then the use I get out of it...but when I need a truck, I have one.
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From: Virginia
No I don't have an AFR meter. The engine description is in my signature but it is a 351W, internally stock but with shorty headers, Edelbrock carb and intake, and recurved DS2 distributor. It is in an F250 4x4 with C-6 trans and 3.55 gearing. My current mileage in mixed driving is 10.5 MPG. I was hoping to move it up to around 12 MPG or so at least. Current performance is pretty decent on acceleration with no pinging so I thought I may be able to lean it out a bit to pick up a little more MPG.
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Thread Starter
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Laughing Gas
Joined: Aug 2010
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From: Northern Kentucky
I am running stock size tires and about 50 psi, and the front hubs are not locked in unless needed. Being a 250 4x4 it sits a bit high but is not lifted. I do have a tube bumper on the front (truck had a plow on it when I bought, since removed) and the comments about front air drag may have merit. I may look into building some type of rolled pan for under the bumper.
I think leaning the carb. will have greater chance of improving MPG over a timing adjustment, so I will give that a try, while watching for signs of going too lean. May have to check into an AFR gauge. Since I have dual exhausts with H-pipe I could locate the sensor in the H cross-over.
Dave: your confusion over the transmission may be based on the reference to Hurst shifter but the PRO-MATIC is a floor mount auto trans ratchet shifter.
ETA I have 2 other vehicles that get 20 MPG or better. but I love driving my truck and working to make it better, thus the question.
I think leaning the carb. will have greater chance of improving MPG over a timing adjustment, so I will give that a try, while watching for signs of going too lean. May have to check into an AFR gauge. Since I have dual exhausts with H-pipe I could locate the sensor in the H cross-over.
Dave: your confusion over the transmission may be based on the reference to Hurst shifter but the PRO-MATIC is a floor mount auto trans ratchet shifter.
ETA I have 2 other vehicles that get 20 MPG or better. but I love driving my truck and working to make it better, thus the question.
Last edited by whisler; Aug 20, 2023 at 07:12 PM. Reason: clarification
5th Wheeling
Joined: Jun 2021
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I have to be honest, all my friends and family that had these era of trucks never ever got decent mileage. Not that a lot was ever done to try and improve it..but anyhow 8-12 mpg is about all I ever knew of 300,303,351..my old man did decent but he had 2wd and DROVE IT LIKE AN OLD MAN. -This might be key-
I like hearing all the ideas though, plenty of people in here a lot sharper than I. When I get mine done I’m going to try to squeak all I can out of it using these tips.
I like hearing all the ideas though, plenty of people in here a lot sharper than I. When I get mine done I’m going to try to squeak all I can out of it using these tips.
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Well I am an old man but I don't always drive like one. You're right about driving style. Especially if you have a 4 barrel carb and a heavy foot. The AT is another element in fuel mileage and knowing your trans shift points and knowing how to feather the gas pedal on the gear change can milk a few extra miles. I drive a manual so I can make clean energy efficient shifts with ease.
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From: Angier, NC
What I posted I cant say any 1 thing will be a big pay back but each 1 giving a little should add up to a total that may be pretty good.
As for mounting the AFR prob in the H pipe I dont think is a good place.
It has to be close to heat from the heads to work right and I dont think it would get the heat in the H pipe.
Being you have a V8 I think you will need to pick 1 side or the other of the Y pipe.
Because I run EFI manifolds, shorty headers, into a Y pipe.
The factory Y pipe has a O2 bung and that is where the AFR prob is.
FYI the AFR prob is a O2 hooked to a gauge.
Dave ----
As for mounting the AFR prob in the H pipe I dont think is a good place.
It has to be close to heat from the heads to work right and I dont think it would get the heat in the H pipe.
Being you have a V8 I think you will need to pick 1 side or the other of the Y pipe.
Because I run EFI manifolds, shorty headers, into a Y pipe.
The factory Y pipe has a O2 bung and that is where the AFR prob is.
FYI the AFR prob is a O2 hooked to a gauge.
Dave ----
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