JCW and Prime

That's a great week dtb and getting good mpg......I've been hearing different things about rpms when downshifting(900....1200) what's the suggested rpm and what's best for mpg

 

Mileage... been doing this awhile guys. What I do works - I got 7.5 out of a Century with a DD60. That takes work. So - you can pay attention or you can blow me off, I don't really care. I understand the PeterPackers run differently, so some of this won't necessarily apply to you guys...

1. Slow down. If you can get to your next stop doing 55, do 55. Its physics. If you're running down the road faster than you have to, your mileage will suffer.

2. The only time you should have the pedal to to metal is starting a hard pull on a hill. Otherwise you are wasting fuel - and that includes entrance ramps to the big road. You are driving a 80,000-or-so pound commercial vehicle, not a sports car. If you merge at 45 mph, so what? Put on your 4-ways and accelerate slowly.

3. Do your progressive shifting whenever your GVW will allow. Heavy and starting up a hill will require more RPM. The same goes when you're in stop n' go traffic - accelerate slowly. So what if the 4-wheelers are late for their next latte? LOL!

4. Don't try accelerating up a hill. Take what you have up to the crest, and then accelerate. Downshift early... just pushing it up the hill at your downshift point burns more fuel than dropping a gear. The transmission acts as a torque multiplier... torque is what gets you over the hills.

5. In moderate hills, kick off the cruise and drive manually. Add some power just before you start up to get you up to the top, let gravity help accelerate you back to speed going down. The cruise control is stupid... it does okay on the flat, but over a certain point all it knows is pedal to the metal - that wastes fuel. You can anticipate what is going to happen in terms of terrain. It can't.

6. When exiting the interstate back off the power before you get to the ramp, and coast some to get some energy back.

7. TIRE PRESSURE, TIRE PRESSURE, TIRE PRESSURE! If you're not checking it before you start every day, you're slacking.

8. Next well-digger's arse cold morning, get out there and make sure your air-to-air clamps are tight! BEFORE you get your engine warm.

9. After you get it started, warm up in low idle for a couple of minutes, and then bump it up to fast idle in cold weather - while you check those dang tires. You'll burn less fuel warming the engine up before you start than you will trying to get it warm going down the road.

10. Never waste a good deadhead - always go slow and pad your fuel economy.

11. Heavy on the tandems will burn a lot of fuel... go a little heavier (not much more than a 1000 lbs) on the drives. Helps in the winter too. Slide it into the 4th hole when you deadhead.

12. If you have a turbo boost gage, drive it - not the speedometer. Try to keep your boost under 10 lbs.

13. If you still can't get it up over 7 mpg... consider talking to the shop about it. A leaking air-to-air will rob you of a lot of power, and a prime indication of it is getting better economy at higher speeds than lower. Also, if there are a lot of miles on your truck, the overhead may need to be set.

It ain't rocket science, and as much as 30% difference in fuel mileage can be attributed to your technique. If you're considering leasing at some point, you've got to be able to get in the mid 7's consistantly to make money. The fuel island will eat what you have left for yourself almost as fast as those dang advances for the next fancy gadget at inflated truckstop prices.

Good Truckin'!

 

thanks ip, maybe a few of those tips, if i can get in habit of doing them, might push me over the 8.0 average mark.

 

Carry up to an extra 1k on your drives?

The closer to balance between the drives and tandems the better the fuel milage in a legal pin setting. Do we need to get out a physics book? Direction of forces, friction and work applied?

The weight carried on the drives should be less than 400-500lbs. You can only fine tune balance within 400-500 lbs per hole on our trailers. So any amount leftover has to go to one or the other... so yes its better to carry it than to drag it.

You can argue about 1k lbs more traction to the tractor on slick roads. And I can argue that its 1k lbs less weight holding the rear of the trailer to those slick roads.

Downshift early when climbing a hill? Where does this come from? You are the first person I have ever hear of that suggests downshifting early.

I climb hills in the highest gear possible that allows me to maintain 1150 RPM. I downshift at 900-950. That allows me to get back in the throttle closer to that 1150-1200 range in the new gear that I am looking to climb with. If the RPMs continue to fall as I ease into 1150 RPM on the new gear... I do the same thing, I stay in the throttle as the RPMs fall, and I downshift at 900-950.

I repeat until I can climb the hill and maintain a climbing rpm at 1150.

If running a Century is the gold standard by which you atribute your acomplishment.... I ran a Century until last week. I got high 7s and low 8s.

 

That's IP/U2 for your comments as both were noted I guess its best what works for the truck b/c mg reefer trainer leaned more to what U2 is doing but flatbed leans more to IP when it comes to downshifting I want to get the best mpg possible when I get mpg possible when I get my truck in the beginning of Dec. So I will keep what you both said in mind and see what works

 

I can show you the numbers...

I kept very detailed records, and still have them. My first inclination was that having equal weight on the drives and tandems was the way to go. It just makes sense. I repeated that experiment a number of times, and always came out with better mileage with a little more on the drives than the tandems.

As far as downshifting early, you hear a lot of guys who just want to leave it in a higher gear as long as they can. Maintaining around 1100 RPM is what you want, but as the grade saps your ability to maintain that level there's no point in trying to avoid downshifting. A fella with a pyrometer that measures exhaust gas temperature showed me that the temp rises rapidly as you start to drop below the bottom of the powerband, indicating that all you're doing is pouring more fuel into a loosing game.

Like I said U2... I still have the numbers and would be happy to show them to you. You might want to try the experiment yourself...

 

What are tandems? Sliding? Yall do have that chute in there.... Ahh the games reefers play Lol Reckon I'll just have to have my trailer loaded right. It works differently over here. I try to get more weight on my drives. Otherwise it just feels like your dragging the trailer around with you. Doesn't handle well like that.

 

just thought about something, im sure i know the answer to, but doesnt hurt to ask.
k, i know optimal, stay below 1300 rpm. but during downhill, rpm's reach 15 to 16, fuel intake during that period is minimal? and yes i have heard of those that shift to neutral, which seems like a bad idea to me for the most part.

 

With the jake on, the ECM is not allowing the injectors to fire. Also just going down a slight slope with your foot off of the pedal, cruise on or off shouldn't have the injectors firing either.

And yeah, freewheeling down a hill is a really bad idea. A good way to get a personal visit with safety.