MPG difference with 2F engine between 4 speed and h55f 5 speed (1 Viewer)

[POPO AGIE]

Even diesels won’t give you much of an economy bump. They are just tractors with awful aerodynamics and like to rev low. You will never see mpg money back on a 5spd swap and for sure never on a diesel swap u less you get the stuff very very cheap.

I’ve got a 1988 BJ74, (like a “modern” FJ40) 4cyl turbo diesel, H55f and I’ve averaged 20mpg for over 5 years of tracking and 60k miles. Best almost all highway was 24mpg. That’s city/hwy winter summer etc. most of the time it’s 44-60mph and back roads. That’s 6-8mpg better than a 40 on average with the added cost of diesel.


Cheapest way to improve your mpg? Buy a Corolla .

That is still better then a 2F or 155F with a 4 or 5 speed. I am not expecting a big difference but 20 mpg from my R2.8 would be fine with me and having more power then either of the F motors I had.

 

[hobbes]

Even diesels won’t give you much of an economy bump. They are just tractors with awful aerodynamics and like to rev low. You will never see mpg money back on a 5spd swap and for sure never on a diesel swap u less you get the stuff very very cheap.

I’ve got a 1988 BJ74, (like a “modern” FJ40) 4cyl turbo diesel, H55f and I’ve averaged 20mpg for over 5 years of tracking and 60k miles. Best almost all highway was 24mpg. That’s city/hwy winter summer etc. most of the time it’s 44-60mph and back roads. That’s 6-8mpg better than a 40 on average with the added cost of diesel.


Cheapest way to improve your mpg? Buy a Corolla .

I always thought the BJ4xs should have come with a 13BT. Nice package that suit each other (I know the 13BT was a bit later than the BJ4xs). But they're hens teeth now...

 

[Hokie LX]

My experience is in a 2F 60 with 33" tires and 3.73 gears but I'll share for reference. I did see an increase with my H55.

At 70mph with the 4-spd I was getting 11-12mpg. With the H55 at 70-75mph, I get 14-16mpg depending on how many mountains on my trip. My 2F is stock with a header. 75mph in my truck is ~2500rpm with the H55 compared to ~3000 with the H42.

 

[knuckle47]

I had a 14B diesel that ran about 16mpg but my Chevrolet 3.0L Silverado runs between 29 and 37mpg and rides lake a Cadillac . Here in NJ I paid $3.53/gal for diesel fuel yesterday and $3.30 for #2 heating oil last week

 

[cvan1971man]

Even diesels won’t give you much of an economy bump. They are just tractors with awful aerodynamics and like to rev low. You will never see mpg money back on a 5spd swap and for sure never on a diesel swap u less you get the stuff very very cheap.

I’ve got a 1988 BJ74, (like a “modern” FJ40) 4cyl turbo diesel, H55f and I’ve averaged 20mpg for over 5 years of tracking and 60k miles. Best almost all highway was 24mpg. That’s city/hwy winter summer etc. most of the time it’s 44-60mph and back roads. That’s 6-8mpg better than a 40 on average with the added cost of diesel.


Cheapest way to improve your mpg? Buy a Corolla .

This is what i was looking for. thank you.

 

[POPO AGIE]

I have had a diesel truck since 1995 and the first was 7.3 IDI NA. Not a lot of power and got about 11 mpg with the 5-speed manual. But for how I used the truck was an improvement over the Dodge 1/2 ton with a 318 and 4-speed that didn't get good milage and as I added weight it took longer to get to speed. Any diesel I had didn't care about additional load but you don't drive them the same as a gas engine. The 7.3 you had to look farther down the road and make sure you had room to pull out into traffic.

As a heavy equipment operator I learned that I could get more work out of a diesel engine vs a gas engine.

 

[trainbufftony]

With good fuel correct timing, and a fresh valve adjustment i got 18 out of my FJ55. (3sp 1f, 4.11s and 31 inch Cooper tires.)
Everything has got to be just so for that to happen...
The 5 speed will be nicer to drive by a country mile, but your mileage is going to be set by a combination of many other factors.
Tire inflation
Alignment
Tire width
Vehicle cross section (lift the truck mileage goes down)
Roof racks and extra lights, really anything you have to push through the air tanks the fuel economy as speed goes up, and it's an exponential curve.
Fuel quality.
Alot will be on the driver:
Stick your foot deep in it and you can really suck down the fuel.
Drive at 45-50mph don't try to out accelerate the modern cars and you can get good enough mileage to justify using it as a daily driver.

 

[POPO AGIE]

Since I started driving my own diesels I wont go back to a gas engine regardless of fuel mileage. When I have worked in Europe or Latin America it was great to be given a diesel powered rental car they were more fun to drive then the gas cars.

 

[White Stripe]

I have gone from fruita Colorado to Georgetown on i70 on one tank of gas. I have a sm465 and 35" tires. The 2f has efi. I have heard of Chet Wagner's custom port injected 2f getting 18-19mpg.

 

[cvan1971man]

I have gone from fruita Colorado to Georgetown on i70 on one tank of gas. I have a sm465 and 35" tires. The 2f has efi. I have heard of Chet Wagner's custom port injected 2f getting 18-19mpg.

I miss living in Co. That is pretty good. I don't know Chet, is he on Mud? Or where else can I look at what he has done?

 

[cvan1971man]

I have gone from fruita Colorado to Georgetown on i70 on one tank of gas. I have a sm465 and 35" tires. The 2f has efi. I have heard of Chet Wagner's custom port injected 2f getting 18-19mpg.

is all that Chet did, was a custom port injection on his 2F? Anything else that could have made it better? And how reliable are those numbers? Everyone says that I am beating my head against a wall due the non-existant aerodynamics of an FJ40!

 

[NOSAJ]

I guess I’m pessimistic in my this regard because I’ve been down this road. I’d say give up on getting significant mileage out of a 2F. I’ve owned my ‘77 for 25 years now, rebuilt the engine in 2002. I still run the stock carb and adjust the valves and mileage has always been 9-11 mpg. Then look at the current prices to rebuild a 2F, adding a cam, then the custom tuned port injection and you are really going to be up there in $$ to save a little gas money. I’ve asked about the sniper and Howell injection and no one running them says they help on mpg. I even got vacuum gauge and watch how I drove and really watched the needle and when it sucked the gas, and I drove like a grandma. I decided just to enjoy the truck for what it is. I own a fleet of diesel trucks for my business and about 5 Land Cruisers of different years for our family. My 6.7 f250 gets the best mileage of any of them at 15-18. My wife’s built 2001 lx470 gets about only about 13 with lift big tires etc. I guess I just don’t care about fuel anymore and enjoy driving big and interesting vehicles. I just finished my diesel HJ45 and haven’t even run a complete tank of diesel through it so it will be interesting to see what it gets. Toyota trucks are reliable but they aren’t fuel efficient except maybe the Tacoma. Even the current Tundra mileage is terrible. My buddy’s big Tahoe gets better mileage than any of our Toyotas. If I wanted to save money on fuel and drive something plain and boring I’d get a Prius. When we had kids everyone told me to buy a minivan…nope not me.

 

[White Stripe]

is all that Chet did, was a custom port injection on his 2F? Anything else that could have made it better? And how reliable are those numbers? Everyone says that I am beating my head against a wall due the non-existant aerodynamics of an FJ40!

He said that it was at 55mph. Air fuel ratio and Ignition timing are major factors whether it's port injection, carburetor, or tbi. At highway cruise rpm, whatever that rpm, the afr and timing at that rpm are what will affect your mpg. In order to find your air fuel ratio, you will need a afr gauge. Aerodynamics are also a factor, but you can't control that, but that doesn't mean you can't improve it with afr and timing. With my efi I can control the fuel and timing with programming. With a carburetor you can still control it mechanically.

 

[cvan1971man]

I guess I’m pessimistic in my this regard because I’ve been down this road. I’d say give up on getting significant mileage out of a 2F. I’ve owned my ‘77 for 25 years now, rebuilt the engine in 2002. I still run the stock carb and adjust the valves and mileage has always been 9-11 mpg. Then look at the current prices to rebuild a 2F, adding a cam, then the custom tuned port injection and you are really going to be up there in $$ to save a little gas money. I’ve asked about the sniper and Howell injection and no one running them says they help on mpg. I even got vacuum gauge and watch how I drove and really watched the needle and when it sucked the gas, and I drove like a grandma. I decided just to enjoy the truck for what it is. I own a fleet of diesel trucks for my business and about 5 Land Cruisers of different years for our family. My 6.7 f250 gets the best mileage of any of them at 15-18. My wife’s built 2001 lx470 gets about only about 13 with lift big tires etc. I guess I just don’t care about fuel anymore and enjoy driving big and interesting vehicles. I just finished my diesel HJ45 and haven’t even run a complete tank of diesel through it so it will be interesting to see what it gets. Toyota trucks are reliable but they aren’t fuel efficient except maybe the Tacoma. Even the current Tundra mileage is terrible. My buddy’s big Tahoe gets better mileage than any of our Toyotas. If I wanted to save money on fuel and drive something plain and boring I’d get a Prius. When we had kids everyone told me to buy a minivan…nope not me.

That is great info. he is getting about 12-13MPG doing 75 on the 186 miles between home and A&M. I guess that is not that bad. I would imagine if he dropped that to 65, he might get 14. I guess that isn't that bad considering it is like pushing a sheet of plywood against the wind

 

[pb4ugo]

I guess I’m pessimistic in my this regard because I’ve been down this road. I’d say give up on getting significant mileage out of a 2F. I’ve owned my ‘77 for 25 years now, rebuilt the engine in 2002. I still run the stock carb and adjust the valves and mileage has always been 9-11 mpg. Then look at the current prices to rebuild a 2F, adding a cam, then the custom tuned port injection and you are really going to be up there in $$ to save a little gas money. I’ve asked about the sniper and Howell injection and no one running them says they help on mpg. I even got vacuum gauge and watch how I drove and really watched the needle and when it sucked the gas, and I drove like a grandma. I decided just to enjoy the truck for what it is. I own a fleet of diesel trucks for my business and about 5 Land Cruisers of different years for our family. My 6.7 f250 gets the best mileage of any of them at 15-18. My wife’s built 2001 lx470 gets about only about 13 with lift big tires etc. I guess I just don’t care about fuel anymore and enjoy driving big and interesting vehicles. I just finished my diesel HJ45 and haven’t even run a complete tank of diesel through it so it will be interesting to see what it gets. Toyota trucks are reliable but they aren’t fuel efficient except maybe the Tacoma. Even the current Tundra mileage is terrible. My buddy’s big Tahoe gets better mileage than any of our Toyotas. If I wanted to save money on fuel and drive something plain and boring I’d get a Prius. When we had kids everyone told me to buy a minivan…nope not me.

^^^^this^^^^^^

is all that Chet did, was a custom port injection on his 2F? Anything else that could have made it better? And how reliable are those numbers? Everyone says that I am beating my head against a wall due the non-existant aerodynamics of an FJ40!

Everybody stretches the truth when it comes to mpg's. Instead of an engine swap buy him a beater that gets 25 mpgs or more for long distances. My round trip to work is over 60 miles a day. I pick and choose nice days during the summer when I want to drive my 40.

 

[sogncab]

As a heavy equipment operator I learned that I could get more work out of a diesel engine vs a gas engine.

The problem is they took an extremely simple fuel system and ruined it then threw the time bomb emissions equipment on. My 18 RAM RAM ruined me for modern diesels. Gutless and terrible mileage. I've been running gas since. Also gutless, and marginally worse mileage, but cheaper to acquire, operate, and maintain.

If they'd build a modern pickup that I'd consider owning out of warranty, I'd supercharge my pickup.

 

[POPO AGIE]

My 2018 RAM 3500 works very well for me. More power then I need and good mileage. The best automatic transmission I have ever had and I don't like automatics. It is in the right gear for the situation and works well with the exhaust brake.

The 2012 2500 had the Chrysler 6 speed that wanted to be in 6th with the torque converter locked at 35mph so I manually shifted that one with the floor shift. It had 4:10 gears and had plenty of power but worked way to hard so mileage was not good.

The 2005 2500 was the last 5.9 I had and it was the G56 transmission and it has plenty of power and better mileage then the dually. I had a full set of gauges to keep an eye on things including transmission oil temp.

 

[sogncab]

The 2005 2500 was the last 5.9 I had and it was the G56 transmission and it has plenty of power and better mileage then the dually. I had a full set of gauges to keep an eye on things including transmission oil temp.

My 18 was a G56. It shifted nice but that tranny was made of butter. I much preferred my 2001 with the NV5600. That was a solid transmission. The 01 was the best pickup I've ever owned. Good mileage, excellent power, and 300k miles with very few problems.

 

[POPO AGIE]

I towed with the G56 and heat was there problem, I installed coolers on the PTO covers and had a temp gauge and never had any issues with it. If I had kept the truck the next oil change in the transmission would have a 30W gear oil instead of ATF.

NV went out of business and Mercedes forced the G56 on Dodge, they were made in Brazil and were not even rated for the output of the 5.9.

 

[bernardbar3]

I had consider this mod… @wngrog gave me the best advice I could find. It’s a bigger modification to the tunnel cover and my best option in his thinking was to swap the 4.11 gears in the diff to 3.70. I have acquired these differentials and will be making that swap this summer.

It should have been finished by now but an option popped up for another project that took 6 months to finish so I’ll document the before and after stats when it gets completed. Hoping to start early April ‘25

I've been entertaining the same thought. Putting a 5 speed (H55F) in my FJ43 a header and disk brakes on the front? Following.