Speed vs mpg

We are in agreement and I second that running slower saves fuel and that lugging an engine actually hurts fuel economy. When I am loaded I am aerodynamically challenged and I choose to run differently than I do mty as far as higher speed and rpms approaching hills. I don’t really worry so much about improving my fuel economy as much as I want to keep a close eye on what my fuel economy is. It is one of my indicators on the health of my engine, IE overhead set properly as one example. When I work a 6 or 7 hour day I am usually one of the slower trucks. When I am working 10-12 hours I tend to get on down the road. Either way I still am very aware of what I estimate my mileage to be and when I top off I check it with pen and paper.

 

I know that rpm"s is what "hurts ya". Gotta keep rpm"s down outta the gate.Sure Frito Lay will "Honk at Ya".Who cares...a couple 100 rpms is apparently .50 miles per gallon over time.Im hauling light loads...got 9.41 mpg last week.Whaat ,ya say? Used about $186 less fuel than "Shad" last week.No BS.Drivin like an eggshell under the pedal.Nothing to prove anymore..."Hey.Go Around"..if You Dont like it its "No Hair off My Back". Im "Spoiled" ...Hourly.Hey...Im Not Holding you up? "Marion Andrusie". Lol

 

Yes this is right.

 

Go around Me. How many lanes do you need? Lol

 

I have a 97 379 with Cat 550 13spd 3.70 gear and 24.5 tires. At 75mph it will get from 4.3 to 5.5 mpg. I did that the first 2 years I owned it.

In the last 14 years I have set the cruise at 60mph and have been averaging 6.8 pretty consistently. I've had over dimensional loads drag it down to 5.9 and low loads get up to 7.3 but, on average it's usually at 6.8 at fill ups. Slowing down has saved me thousands in fuel costs over the years not to mention it's a much more relaxed pace and I feel a lot safer behind the wheel.

That's an average of 2 whole miles to the gallon more. I have yet to try 55mph.

 

55 to 59 isn't as great a change as from 59 to 62. 4-mph increase versus 3.

62-64 keeps one close enough to the average to make managing overtaking traffic less of a burden than at 59.

Over 58, but under 65, makes a friction-free day.

And you WILL NOT be as tired at the end of the day.

Also, given that one can also take in more of the passing scenery, it’s also good for the spirit.

 

Put 3.55 gears in it and you can run a little fater and get the same mileage.

 

Thought about that but, this type of truck seems sensitive to speed as far as aerodynamics go.

Regarding overtaking traffic or creating a log jam, every once in a while I'll have to use the power this truck has to avoid or, not create a situation like that. For the most part everyone seems to get around me trouble free without complaints. This trucks been dynoed at 18 and change ft lbs and 510 hp at the rear wheels so it can move out of the way pretty quick to maintain flow. Again I rarely need to though.

 

Weight in the box was always my biggest factor for mpg. I guess if you’re always 80,000 lbs going slow helps but stay below 55-60000lbs good mpg is easy along with 700 plus mile days.

 

A lot of getting good fuel mileage is how you drive rather than what speed you're going. Are you hammering down up the hills, accelerating at full boost/torque, going full speed to a red light then having to come to a complete stop and starting over again, or driving both feet on the floor even downhill?

It's usually not going 75 when it's flat that kills your fuel mileage, it's the way you get to 75, and also if you're trying to stay at 75 going up hill.