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It increases exponentially with speed, while road speed increases linearly. Why don't you trust it? It might be out 2-3 tenths of a MPG. But here's the trick, it will always be out the same amount! Wind resistance increases 36% from 60 mph to 70 mph. Proper specs will help, but theres NO substitute for slowing down. |
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This is the whole reason we had the National speed limit of 55MPH for a while, during the alleged fuel shortage. It is absolutely true, air resistance is a huge factor and the drag increases exponentially with increased speed. Going under 55MPH is even better. But I think most experts will agree, that 60MPH is the breaking point for fuel consumption, so to speak. |
Thanks for all the great feedback. Mostly what I expected.
So, if YOU were going to buy a new truck, and you had a very tight budget, what would you buy? Anyone who says Mack gets a time out in the corner! I pull a flatbed, so I can save some air drag with a lower profile. I want the 13 speed, or similar, because with the 10 speed, I just loose too much speed between shifts going up hills. And, I'm sure it sucks up the go-juice between shifts when I wind 'er out to 2200 RPM because I know she'll drop to 1300 after I shift and fall on her face. (slight exaggeration, but ya' know wutimean). I don't care about the fancy stuff, I just want to make money. I'm partial to Caterpillar, (probably because I used to run Cat equipment). This truck sounds pretty good, maybe in a 2008 model: (does it come in pink?) LOL, Ha ha ha... 2004 International 9400 with a wind deflector on the roof .. pulling 53" dry van. I have a 475 hp CAT with 1,650 lb/ft torque, 13 speed tranny with 0.73 top gear ratio, and 3.73 rears. I recently switched to low profile tires and I dropped a mile on the speedometer at the same RPM. I get decent fuel mileage (between 6 and 7 mpg) even fully loaded but only because I stay within the engine recommended RPMs. For my CAT, it's 1,300 to 1,400 RPM. I usually do 58 mph with a light load (1,300 rpm) and 60 mph with heavy load in hilly terrain (1,350 rpm). |
i.m.o you cannot beat a det on fuel mileage. at least the 95 i have.
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You can't beat a detroit for fuel mileage if you're doing lighter work. If you're buying used on a tight budget get a DD that been rebuilt with warranty because the older have a nasty habit of throwing rods through the block with little warning. I'd probably advise a N-14 style Cummins for a good balance between fuel economy and power. CATS are nice but parts are expensive if you get a bad one and the later ones seem hard on fuel. This is assuming your buying a used truck in the 98 and newer era.
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I'll take the N14 over the Cat or Detroit any day of the year.
I think Detroit did finally remedy that wrist pin bushing problem. But who's to say, if you buy an older one, that the right parts were used. When they turned loose, they sure did ruin a block! |
My Pete 359, Cummins 400, 13speed, 2:89 rears, now retired as a living van, used, with flat bed, loaded with low profile loads, to get 7.5 mpg, keeping about 60. Now, with no trailer, 3 ft extension in the frame, and a 26ft low profile box converted to live in, I am getting the best mileage of my truck's life. I once got 10.5 mpg, at 55mph, level ground, no wind, on I10. I usually get about 8.5 - I keep the speed to 60, I am not in a hurry. If I go 70 or higher, even my almost unloaded home goes from 8.5 right down to 5. Current constant weight is 28950.
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That sounds cool, Wild Bill.
That brings up another question. How much difference should one expect between flatbed v. Van? I'm told that flatbeds typically get worse fuel mileage because the tarps really 'grab' the air. But it sounds like you did OK. |
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"Route selection: Interstate v. congested road= 20%" I typically get routed over the SHORTEST route, which is typically the most traffic and most big steep hills. I prefer to take the longer, less traffic route and if possible, flatter. For you guys who run the Northeast, here's a typical example: I-95 from New Hampshire to I-495 to I-290 to I-90 to I-84 to I-91 to I-95 to NYC (George Washington Bridge) to I-287 to I-78 to I-81 and on South. or I-95 from New Hampshire to I-495 to I-290 to I-90 to I-84 to I-81 (in Scranton, PA) and South. The latter is 25 miles longer, but typically saves me 2 to 5 hours of traffic jambs. The 'company' wants me to take the 'shorter' route and sit in traffic. How much is too much, and at what point do the miles cost more than the traffic? Judging from this example, I'd guess I could go up to 20% more miles without burning more fuel. |
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And another thing;- miles not only burn fuel... So it's individual decision, and should be taken on case to case basis! :wink: 8) |
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