8 mpg by driving 55

I believe is lower, i did many tests on my truck, the air resistance and tires rolling resistance is increasing exponentially with speed above 50-55 mph. I get about half a mile per gallon better fuel economy reducing from 62 to 55mpg, yes too slow not practical. Try different speed record your mpg, find your truck sweet spot.

 

Naw, I get 5 mpg, but I try to run faster than anyone else on the road. Bull hauler's be ######...

 

At 5mpg you're doing better than that empty bullrack, those things pull like a freaking ##### empty I don't know why.

 

Rough estimate is 1 to 1.5 gallons an hour idling.

 

Wind goes in the holes on the side . Beats on the doors in the back causes resistance. That would be my guess. When I hauled storage sheds if the garage door was up facing the front, they would pull like a mother.

 

Would you say they do better when full or that they don't do as good as they should when empty?

I think it's from all the holes in the sides. Iv'e noticed some flatbed loads like metal decking suck way more than would seem reasonable. It's usually a square load but there is a bunch of dunnage sticking out 4-6' on each side. 4-8 layers with 8-10 pieces of dunnage per layer. Porcupine load really drags.

Time for Air tabs?

 

I imagine it's the holes in the sides, they do pull better full, you don't get much better fuel mileage but it does pull better, been my limited experience anyway. One guy I know of claims 4.8 for an average with a 750 horse cat, that's not too bad pulling one of those things. Don't think air tabs would help a whole lot there.

 

The sweet spot is entirely dependent upon how the truck is spec'd. The engine is MOST efficient within a narrow portion of it's operating range...and whatever road speed the truck happens to be traveling at that engine speed is going to give you the best fuel mileage for that gear.

Gear selection matters, too, because if your goal is to maximize fuel efficiency, you'll want to reduce losses in your drive train. A 1:1 gear ratio through the transmission is more efficient than an overdrive...but if you plan to run in direct, you need rear end gearing that is compatible. Tire size also affects the overall equation and needs to be considered.

Personally, fuel mileage has never been a top concern of mine. I need the truck to do the job I'm asking it to do, no matter what that job happens to be. I need to get what needs to be done completed and get home within the scope of the HOS. If getting better fuel mileage requires spec'ing a truck that can't do the job as well, or driving in a manner that extends the day beyond what can be accomplished legally within the HOS, then it isn't something I would be inclined to focus on. Get paid more for what you do, and you don't have to pinch pennies trying to do it.

 

My old Detroit burned around 8/10 an hr . This one old as it is always at 1 gal per hour

 

Depends on max torque range I believe My 12.7 most efficient between 1350. - 1650 rpm anything over 1700 or so is a waste.My last Truck w/same set up did best at 13.75 rpm according to On dash computer after a lot of trying different things. If I ran it barely to top of small hill while letting up on fuel then top w/out dropping gear then give very little on down side I could really do good . Got tired of that real quick. My times worth something too.

 

I was getting 7.3 but I have new Yokohama instead of michillin and now it's 6.8 with super singles and a tanker. I idle two hours at night.