Why don't trucks go 55 for fuel efficiency?

Fuel mileage at different speeds are determined by gearing and how much pedal you put into it. Different trucks are different and they are NOT the same today as they were when you needed four hands to shift. Get off it.

 

Normal acceleration.

The sooner you get to speed. The sooner you can relax the pedal and maintain speed.

My car does better that way anyways. Over a soft pedal spending more time trying to get to speed.

The difference between light and full is minimal.

Now if you're talking carb car. Then your theory might work. But with today's ccomputer controlled direct injection. It's 6s.

My Vega was a 20 mpg car that cruised around at 2500 rpm. My Cruze Is a 42 mpg car and cruises around at 1500 rpm. It also burns more fuel at slower acceleration due to more time spent with open throttle getting up to speed.

10 gph at 2 minutes acceleration vs. 9.9 gph at 30 seconds acceleration. Drops me from 42 to 40. With the traffic lights.

 

You said a true thing, kinda...congratulations

Things affecting fuel mileage in a big way


1. Running the right rpm for the gearing and engine
2. Wind resistance (speed and weather dependent, also load for flatbed) though only really pertains to 50+mph, under that it is quite negligible and is less impactful than even weight
3. Terrain (though this is more affected the heavier you are, less when empty)
4. Open road vs stop/go/tons of stoplights
5. Idle time (not technically a mpg thing, and at say 75% idle time this could be more impactful)
5. Weight

Thats the rank order of what i have noticed keeping track of weight and fuel and style and types of driving as affecting fuel mileage.

But we are forgetting the number 1 thing that affects fuel cost in cpm....
Price at the pump, so geography/taxes. I changed my tires back down to the right thing for my setup, my mpg jumped on average .75 mpg, but at the same time the fuel price jumped, wiped out the gains, then someone decided that i should live in pa during the week and my fuel cost for the week... grumble

 

You forgot hp.

I do the same trip 4 times a day. I'm in a different truck now. It does the same trip 5 minutes faster. And gets .8 mpg better..Then the last truck.

Trucks that get there faster use less fuel. They spend less time climbing mountains with WOT. Less time accelerating to speed.

Every 500+ hp truck I've been in has gotten better mileage then all the 450 trucks I've been in. And it's a sweet thing when you can do a 900 mile journey 2 hours faster.

 

Last night I hit the yard with 5 minutes left on my 11. Had I run at 60 instead of 65 for just the last hour of my day I wouldn't have made it. I would have needed to shut down 50 miles away and finish it this morning, leaving me with only 10 hours to run today's loads and get home. With a fresh clock I can do three loads and get home, with only 10 on the 11 I get 2 loads, then go home, or 3 and get home Saturday morning. Pushing "hard" last night is increasing my paycheck by $100 with no real impact on my time at home.

 

We would have never guessed you'd ignore the math disproving your original premise.

A different truck getting better mpg in less time over the same route does not mean a thing except that truck is more efficient than the previous one.

As far as higher hp getting better mileage. That's related to two things : reduced downshifting and there can be some gains by operating lower on the fuelling curve where the BSFC is lower. That second is very much dependent on the power curves for the high vs low power ratings of a given engine family. For example, the S60 ratings varied very little below 1500 rpm. To take advantage of the higher ratings required running at higher rpm (which is where the higher BSFC numbers were) which negated most of the higher power benefit. It also meant there was little real world difference between ratings if they were operated the same.

Fuel economy is the toughest variable to pin down, because their are so many variables. The manufacturers have incredibly detailed protocols for mpg testing, and still run a huge number of repetitions to get an accurate average.

 

We didn't know we was ignoring my premise.

 

I see what you're saying, but I tend to more subscribe to the idea that you kept your driver side door closed. Also, you didn't run into anything that would have derailed you. I almost got derailed yesterday with the most vicious thunderstorm ever in Kansas. That was scary and fun at the same time lol.

 

Ooh ooh i really wanna read the research on aerodynamics over 60mph being ineffective. Please provide or send me in the direction to research.

 

Under 60.