Does speeding save fuel?

Air resistance does have a lot to do with fuel mileage. I was driving a pete with a 3406B without a top air deflector getting 4.9. My co-driver told me to get an air deflector put on top of it and Id save on fuel and the truck would pull better. He was right. Fuel mileage went up to 5.8 and the thing pulled like a car.

 

On my dd15 1450 Rpm "seems" to be the best. Flat ground 62 63 I get very good milleage. On hilly ground its better at 67, where the engine has power. I didn't have to get as deep in the throttle at 67 mph.

 

It depends on more than some pre-determined speed. It depends on the required horsepower needed to keep a truck moving at that speed. So now, are you going eastbound? Wind generally is west to east. Did you just crest the hill east of laramie wy? It is a slight downhill all the way to Omaha. These will be your 2 biggest changing variables when it comes to determining what speed will use the least fuel.

The other half of the equation is what price you're paying for fuel, pre ifta. That is the easiest way to cut your fuel cost. There's lots of threads on that. If you're a company driver you probably don't know the actual price your company is paying after their discount. But you can calculate for your own mental exercise should you be considering owning your own someday. To learn how it works, at least.

The time saved is often not worth the extra expense. The difference in an average speed of 70 vs 60 for a 2500 mile load is only 2:45. And if you schedule your delivery time at 8 am instead of 3 am you have some extra wiggle room. Or you can schedule it as if you have a perfect world and if you manage 70 you will be right on the money. Good luck...

A general rule of thumb is ever 1 mph above 55 will cost you about .1 mpg. If you try it over the long run.... It is not complete b.s. if you've ever seen the charts showing horsepower required as speed increases, you'll see the wind is the #1 pushback rising faster than terrain and tire resistance as speed increases. Ever try to maintain 65 in a very strong headwind and can only manage maybe 60? So find your happy medium and roll with it. I like 62-64 When I go west and when I come back east I prefer 70-75 where the situation allows. If you have a pyro and egt gauges you can get good at this game and have more consistent fuel mileage while varying your speed for conditions.

 

The simplest explanation is that when you increase the speed, the air resistance (drag) increases much quicker than the speed, demanding more power and more fuel.

 

There are sweet spots, truck configuration depending. I think, however, that a man has to factor in his mental tolerance for slower speeds. In my case, it exponentially decreases as the speed falls below 65 mph. So even though, it could be thousands of $ saved per year, I'd become even more worn down mentally by this job, if I were to drive at 60 or below all the time. I agree not to save $ in exchange to drive in my comfortable speed zone : > 65 mph.

 

They retired the Concorde (fastest passenger plane in the world) because it cost more in fuel than the passengers paid. Airlines have actually gotten slower in the last 50 years in an effort to maximize profits.

Trucking and truckers are in a unique bind. Limited by time and speed, truckers must find the sweet spot to avoid tickets but also get their loads done on time and efficiently get on to the next load and turn it in before the week's payroll deadline. They wouldn't have to worry about living week to week paychecks if they were paid correctly and were able to amass $25,000 -$35,000 in the bank, but the MAN has it set up to have drivers looking for ways to work more hours and squeeze in more miles within the week's time limits.

 

Slide in behind a bull hauler. If you can keep up buy the mans dinner at the other end of the trip

 

At the end of the day if you honestly calculate your actual time saved to the added cost of fuel you will have to decide between pocketing a extra $100CDN a day or getting home 30 minutes earlier. Not hard to save 80 litres a day.
Mr Hammerdown will always have a argument for running wide open.

 

I drove a 2014 T680 all across the western US for 6 months, and I always did the posted speed limit when conditions permitted, even when it was 80 MPH. My boss said that I was getting much better fuel mileage than the previous driver. An extra 100 miles a day got me home that much sooner at the end of the week.