300 I6 MPG
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Junior User
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300 I6 MPG
Seems from what I read there is a huge variance between average 300 i6 mpgs. I've even been told to get a V8 because it will get better mpg since it wont be working so hard.
I'm wanting to turn my 73 F100 into my daily driver. It came stock with an np435 and 360. Well the 360 is blown so I got a zf5 with a 1356 transfer case and a 300 i6. I think its got a 3.5 rear.
I'm just wondering what to expect from this setup in terms of MPG. I can get a 5.9 cummins for $1700. I've got the 300 i6 for free and would spend $600 in a new intake, exhaust and 4 bbl carb. so its only 1100 more for the diesel.
If I can swing 16-17 mpg highway with the 300 i6 I will happily throw it in but I can get 20-22 with the cummins.
I had an 88 f150 with a c6 tranny and 300 it was efi and only got 12mpg at the best. Owned the truck for 10 years and it never could do better. If thats the best im gonna get then im going cummins. If i can get upper teens with the gasser i will happily put it in.
Just need your guys opinions here....
I'm wanting to turn my 73 F100 into my daily driver. It came stock with an np435 and 360. Well the 360 is blown so I got a zf5 with a 1356 transfer case and a 300 i6. I think its got a 3.5 rear.
I'm just wondering what to expect from this setup in terms of MPG. I can get a 5.9 cummins for $1700. I've got the 300 i6 for free and would spend $600 in a new intake, exhaust and 4 bbl carb. so its only 1100 more for the diesel.
If I can swing 16-17 mpg highway with the 300 i6 I will happily throw it in but I can get 20-22 with the cummins.
I had an 88 f150 with a c6 tranny and 300 it was efi and only got 12mpg at the best. Owned the truck for 10 years and it never could do better. If thats the best im gonna get then im going cummins. If i can get upper teens with the gasser i will happily put it in.
Just need your guys opinions here....
Senior User
Joined: Aug 2010
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From: Sacramento
I can get 15 city and average 14 city in my 72 2wd with a t18 and some new to me 3:73s in the rear, I've gotten 17 on the freeway doing 60 which put my tach at 3000. Thats with a 500cfm 4 bbl and opened up exhaust. As long as you drive appropriately you should get mileage comparable to a 302 possibly better being as my engine never really gets taken over 3k even with a trailer behind it.
Posting Guru
Joined: Jun 2004
Posts: 1,092
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From: Casa Grande
With the overdrive you should be able to do high teens. I run 18+ highway, 14 or so city, with a SROD 4sp O/D and 3.55's on 235 75r15's. That's doing 60-65 highway. But if you want to go Cummins check out the 4bt. It's the 4 cylinder version of the 5.9. Hp and torque stock are about equal to the 300 and can be turned up to around 200hp easily. Plus it bolts in and fits good and only weighs about 100lbs more than the 300.
Posting Guru
Joined: Feb 2002
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From: Atlanta, Georgia, USA
The Cummins will be a lot of work. Fabulous motor for sure, but it's not nearly as easy as the 300 swap. I've seen the Cummins-to-Ford swap done but it took a lot of work to get it right.
+1 with the group on high-teens on MPG. I get high teens on my MAF '95 in Hawaii, which is like crawling through a city in Thailand. In the mainland I've always easily gotten 18-20 with the original factory E40D and 293k miles. It's the best motor you could possibly pick for a truck, and don't buy advice from anybody who think a 300 will be working hard to move a pickup. -TK
+1 with the group on high-teens on MPG. I get high teens on my MAF '95 in Hawaii, which is like crawling through a city in Thailand. In the mainland I've always easily gotten 18-20 with the original factory E40D and 293k miles. It's the best motor you could possibly pick for a truck, and don't buy advice from anybody who think a 300 will be working hard to move a pickup. -TK
Moderator
Joined: Dec 2007
Posts: 7,987
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From: Boise, Idaho
The $1700 for the Cummins is only the price of the engine.
You're probably looking at doubling that by the time you get all the necessary adapters and stuff to get it into the truck.
There are a few who can get reasonable mileage with a V8 (usually 302 owners), but they are the minority. The vast majority of them get worse gas mileage with their V8s on the open interstate than I do with my 300 I6 with short, cold trips around town in the middle of winter.
You're probably looking at doubling that by the time you get all the necessary adapters and stuff to get it into the truck.
There are a few who can get reasonable mileage with a V8 (usually 302 owners), but they are the minority. The vast majority of them get worse gas mileage with their V8s on the open interstate than I do with my 300 I6 with short, cold trips around town in the middle of winter.
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From: Coeur d alene, Id
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Senior User
Joined: Jun 2010
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From: Curwensville,PA
i agree with these guys you should have no prob getting 17 mpg i get 14-15 with 33 inch tires and 236,000 miles on the engine
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Junior User
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I'd like to be able to get around 17-18+ mpg. Would that be easiest with the stock 1bbl carb or could i get the performance upgrades such as efi exhaust, offy intake and an edelbrock 500 and still manage that kind of fuel economy.
I'm basically wondering for a DD to work and back what will net me the best fuel economy with the 5 speed with OD. The stock 1bbl or the upgraded intake/carb.
Thank a lot I really appreciate it, I have learned a lot so far!!!
I'm basically wondering for a DD to work and back what will net me the best fuel economy with the 5 speed with OD. The stock 1bbl or the upgraded intake/carb.
Thank a lot I really appreciate it, I have learned a lot so far!!!
Moderator
Joined: Dec 2007
Posts: 7,987
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From: Boise, Idaho
Your best bet for that would be with the 1bbl and an EFI exhaust. That's the best mileage I ever got. 3.00 with OD transmission. I think I netted around 21 - 23 on one or two trips.
However, 17 - 18 could definitely be possible with a well tuned 4bbl, with the option for WAY more power.
However, 17 - 18 could definitely be possible with a well tuned 4bbl, with the option for WAY more power.
Postmaster
Joined: Mar 2005
Posts: 2,949
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From: Earth
With an Offy C you could split the difference and run a 2bbl carb.
What kind of mileage you get with a 4bbl depends on how heavy your foot gets after the swap. It's certainly a lot more tempting to mash it since the engine actually responds.
What kind of mileage you get with a 4bbl depends on how heavy your foot gets after the swap. It's certainly a lot more tempting to mash it since the engine actually responds.
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To me splitting the difference doesnt mean 2bbl... A 4bbl should almost always out perform a 2bbl because you stay stay out of the secondaries.
I hear a lot of guys talk about getting 19-21mpg with stock setups and only a few guys talking about 16-17 with upgrades. Being a daily driver that will amount to a lot of money after 15k miles in a year.
Just wondering... Im usually a diesel guy but am really drawn to the 300 i6 and have minor experience with gasoline engines and carbs.
I hear a lot of guys talk about getting 19-21mpg with stock setups and only a few guys talking about 16-17 with upgrades. Being a daily driver that will amount to a lot of money after 15k miles in a year.
Just wondering... Im usually a diesel guy but am really drawn to the 300 i6 and have minor experience with gasoline engines and carbs.
Postmaster
Joined: Dec 2006
Posts: 3,603
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From: Spokane, WA
Plenty of threads and comments on this Forum from those getting nothing near 19-21 mpg with stock setups. A 2 bbl is just a 4 bbl without secondaries...theoretically, no difference when running on 2bbls or running on just primaries given an equal cfm between the two.
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Joined: Sep 2010
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From: Carrollton, TX
Hi Folks, I've been battling with this same issue. I have a 1981 Class C RV built on an F250 chassis. It's about 20 ft and weighs about 6500#. It has a 300 with a 1 barrel carb and C6 trans with around 50k (150k ?). I have been stockpiling parts for awhile. So far I have a Offy C, New 2 barrel carb, ZF 5-342, pedal assembly (with clutch), EFI manifolds and Walker Y.
I also have a Cummins 5.9 I pulled from a school bus with only 46k, and a bread truck SBF to Cummins adapter and flywheel that will work with the same trans. Would need to fab motor mounts and exhaust out of the stuff I pulled from the bus.
I think I've decided to install the 300 hop ups and ZF, and see how that works, since thats the easiest route. Mileage and being able to keep up with traffic are my main considerations.
I also have a Cummins 5.9 I pulled from a school bus with only 46k, and a bread truck SBF to Cummins adapter and flywheel that will work with the same trans. Would need to fab motor mounts and exhaust out of the stuff I pulled from the bus.
I think I've decided to install the 300 hop ups and ZF, and see how that works, since thats the easiest route. Mileage and being able to keep up with traffic are my main considerations.
Posting Guru
Joined: Jun 2004
Posts: 1,092
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From: Casa Grande
If it was me I'd do the 5.9. More power and at least as good, if not better, MPG. As for motor mounts you can get them online. I think the company is Ford Cummins. I love my 300 but in reality it can't keep up with the Cummins in power or mpg.