7.3 Powerstroke question

[cfpinz]

The factory mufflers are pretty much straight through if you look through them. Our 99 has straight 5" on it and it's pretty obnoxious but I'm too cheap to spring for a muffler. Also has 285/75/16 tires and they're too big in my opinion. Rob a fair amount of power and not worth a nickel in our red clay.

I'd be more concerned about the mismatched lug nuts, the two that don't match are not the correct profile mating surface for your wheels and may very well loosen up over time. Be a good idea to replace any like that on the truck with factory style for safety purposes.

Nice truck.

 

[greybeard]

They seem to take turns riding shotgun, mostly depends on who loads first.

Can your dog open gates?

 

[Ouachita]

The factory mufflers are pretty much straight through if you look through them. Our 99 has straight 5" on it and it's pretty obnoxious but I'm too cheap to spring for a muffler. Also has 285/75/16 tires and they're too big in my opinion. Rob a fair amount of power and not worth a nickel in our red clay.

I'd be more concerned about the mismatched lug nuts, the two that don't match are not the correct profile mating surface for your wheels and may very well loosen up over time. Be a good idea to replace any like that on the truck with factory style for safety purposes.

Nice truck.

These tires are 265/70/R17 and what I would describe as a touring/highway tread, 31" diameter. I don't want aggressive (loud) tread, just a mild all-terrain. A 33" tire will require an additional 6% torque applied to get the same acceleration. First (second) gear is already a bit low when running empty. Once going thru the gears, shifting at a slightly higher RPM will simulate the torque to final drive.

Wider tires, with the increased frontal area drag, and friction from the width of the contact patch, are more detrimental to fuel mileage than a taller regular width tire, and taller= less rolling resistance.

Yes, the mismatched lug nuts is hokey. The guy I bought it from had some fancy wheels on it. Way too fancy/pretty. So he kept the powder puff wheels and put these on, with some older but matched set of tires, and scrounged some lug nuts. When we made the deal, we were both in a hurry, so I told him not to bother balancing them. I don't know what the wheels and tires he removed cost, but he discounted $2,000.
When I put tires on these wheels, I'm going to install the correct and new nuts, maybe even cabbage on to some center caps.

 

[Ouachita]

Can your dog open gates?

Still working on it. You see, with crew cab, the gate opener can have her own door whether the dog scores shotgun or not (the park brake doesn't work, so with manual trans I have an excuse).

They are well behaved most of the time. Iffin they get outta line, I just push the button. The collar does the rest

 

[HatCreekCattleco]

I have a 96 7.3 and I don't get anywhere close to 26 mpg. Might should leave that exhaust and tires just as they are.

Same here. My 99 might get 12 on a good day. Empty.

 

[Ouachita]

Same here. My 99 might get 12 on a good day. Empty.

Wow, what gives?

 

[GoWyo]

My 1997 CC 4x4 7.3 gets around 14-15 empty. It has E4OD auto trans and stock 235-85R16 tires. I have the shop checking the exhaust headers work they did last fall and then it's going up for sale.

 

[Ouachita]

I had a 2001 Duramax that got 22 running empty, and 2006 Cummins 5.9 that got about the same. Those were both unmolested OEM stock. I assumed this truck would be close to those from that era, but was surprised at 26. I would not have bought it if only 12mpg.

In the last year, the guy replace all 8 injectors, injector harness, fuel pump, the turbo/wastegate assy, up pipes/down pipes, crossover?, and a lot of other new aftermarket goodies. Maybe all these upgrades help efficiency as well has power.

 

[simme]

96 F250 7.3 regular cab 2WD auto - 20 mpg empty on interstate. 11 mpg with stock trailer
99 F350 7.3 crew cab 4WD duals 6 speed manual - 15-16 mpg empty on interstate, 10 mpg with stock trailer

Wife's 2018 Nissan rogue - display says 36 to 42 mpg. 28 actual based on odometer and gallons added at fill-up. For me, gallons bought over multiple tanks and distance traveled is more accurate than a digital display that does not directly measure fuel flow rate.

 

[Ouachita]

96 F250 7.3 regular cab 2WD auto - 20 mpg empty on interstate. 11 mpg with stock trailer
99 F350 7.3 crew cab 4WD duals 6 speed manual - 15-16 mpg empty on interstate, 10 mpg with stock trailer

Wife's 2018 Nissan rogue - display says 36 to 42 mpg. 28 actual based on odometer and gallons added at fill-up. For me, gallons bought over multiple tanks and distance traveled is more accurate than a digital display that does not directly measure fuel flow rate.

I agree with that, but I've verified miles driven and fuel added (using the same pump until auto shutoff). I've only had the truck three weeks and 1300 miles, so as I get more data I may find the average empty mileage settles in at less than 25.8.

I just looked at the original window sticker which shows .373 gears. After a bit of research it appears a special order, and that most one tons came with .410 or .456. That makes quite a difference in economy v. power. This truck gets better mileage whereas your truck would likely run off with a load, leaving me choking diesel smoke.

I'm a couple hours from any highway with greater than 55mph speed limit, and these roads in the Ouachita's aren't much faster than that anyway. The engine is turning 1500rpm at 55mph.
Driving habits, as well as compelled driving technique amongst other traffic, both effect fuel mileage, and I drive like an old man. I still have not buried the foot-feed.

 

[Grayme]

I bought a '99 single wheel one ton and getting ready to put taller tires on it.

The truck has a new exhaust system on it, but the previous owner removed the muffler. The shop must have measured once and cut twice, because there is only one inch between the tire and exhaust pipe.

I'll need to increase that clearance. Easiest/cheapest way is to add a length of straight pipe, but it wouldn't bother me if the truck was quieter.

This rig has been "tuned" or "programmed", whatever it's called, and I love it. It gets 26mpg empty on the highway.

Question- Will installing an OEM type muffler effect the tuning? In other words, if I have a muffler installed, should I expect different performance, or have to re-tune?

I envy you. I have a 99 7.3 I put a tuner on,I get 12mpg full or empty.

 

[GoWyo]

I agree with that, but I've verified miles driven and fuel added (using the same pump until auto shutoff). I've only had the truck three weeks and 1300 miles, so as I get more data I may find the average empty mileage settles in at less than 25.8.

I just looked at the original window sticker which shows .373 gears. After a bit of research it appears a special order, and that most one tons came with .410 or .456. That makes quite a difference in economy v. power. This truck gets better mileage whereas your truck would likely run off with a load, leaving me choking diesel smoke.

I'm a couple hours from any highway with greater than 55mph speed limit, and these roads in the Ouachita's aren't much faster than that anyway. The engine is turning 1500rpm at 55mph.
Driving habits, as well as compelled driving technique amongst other traffic, both effect fuel mileage, and I drive like an old man. I still have not buried the foot-feed.

My 97 has 4.10 gears and spins around 2300-2400 rpm at 70 mph. Keeping it down to 60-65 mph and 2000 rpm helps the fuel economy quite a bit, especially pulling trailers.

 

[HatCreekCattleco]

Wow, what gives?

It's always been around that. I've had it 20 years. It is an automatic 4x4 that might be the difference

 

[HatCreekCattleco]

But I will add it has been one dependable tough truck. Aside from lack of power and poor fuel economy i couldnt ask for a better rig

 

[Named'em Tamed'em]

96 F250 7.3 regular cab 2WD auto - 20 mpg empty on interstate. 11 mpg with stock trailer
99 F350 7.3 crew cab 4WD duals 6 speed manual - 15-16 mpg empty on interstate, 10 mpg with stock trailer

Wife's 2018 Nissan rogue - display says 36 to 42 mpg. 28 actual based on odometer and gallons added at fill-up. For me, gallons bought over multiple tanks and distance traveled is more accurate than a digital display that does not directly measure fuel flow rate.

The digital display is a lie-o-meter!!

Fill it up the same and do the math.

 

[Ouachita]

The digital display is a lie-o-meter!!

Fill it up the same and do the math.

I think simme was suggesting to do the math, and don't trust the mileage display. I agree with that.

I'm baffled and confused. I'm sure there are folks reading this, thinking there's no way that guy is getting twice the mileage.

Then there's at least a couple or three of us saying there's no way those other guys are getting half the mileage.

Something is amiss. I don't know what. There must be a common and identifiable denominator to explain this extreme discrepancy. I'm not savvy enough to make heads or tails out of it.

 

[Named'em Tamed'em]

My '06 dodge 3500 4x4 dually on cruise control at 70 gets 21-22 . Not pulling or in the mountains.

I believe it

 

[SmokinM]

I think simme was suggesting to do the math, and don't trust the mileage display. I agree with that.

I'm baffled and confused. I'm sure there are folks reading this, thinking there's no way that guy is getting twice the mileage.

Then there's at least a couple or three of us saying there's no way those other guys are getting half the mileage.

Something is amiss. I don't know what. There must be a common and identifiable denominator to explain this extreme discrepancy. I'm not savvy enough to make heads or tails out of it.

Could be as simple as the right foot or could be the way they are set up and what they tote around. I have 2 of these trucks, same year same motor one is a F550 and the F350 mentioned above. The 350 will pull circles around the 550 even after I tuned it despite the higher gears etc. F350 gets about 40% better mileage too. That truck with 3.73 rears and the 6 spd. just keeps that motor in the sweet spot especially if you know how to drive it.

 

[kenny thomas]

You bring up a good point. The driver can make some difference in the mileage.
My wife can drive our Durango and get 22. I get over 25 when i drive it.

 

[chevytaHOE5674]

Are you guys sure your odometer is correct? Change in tire size can change the accuracy of the speedometer and odometer.

My 7.3 6 speed 4.10 geared ext cab flat bed gets about 6mpg hooked to a trailer nearly 100% of the time, the rare occasion its unhooked it gets about 14mpg at 60. Much faster than that and the rpms are singing and mileage plummets.

My other 7.3 auto 3.73 geared crew cab gets about 17-18mpg on its best day of 60mph highway cruising.