Getting Better Fuel Mileage - Page 6 - Truckers' Trucking Forum | Message Board

550hpW900L · **^ Top** #51 4 Weeks Ago

Might not hurt the motor, but the rest i dont know.

Brickman · **^ Top** #52 4 Weeks Ago

Most of what was written is pretty good. But I've got to disagree with several points.

Quote:

Vehicle aerodynamics / configuration: This varies greatly with different type of power units and trailers. The best possible is a Cab-over-engine (COE) with roof fairing, side fairings and very few protruding accessories, pulling a smooth side van trailer. Everything having ribbed low pro tires

The worst is a big conventional with no fairings, big external air cleaners , big mirrors, horns, fuel tanks, visors, no fairing, pulling a flatbed with a big bulky load, with lugged tall tires.

It has NOT been my experience that COE gets better MPGs, not even close.

Large car trucks even ones pulling a skate board can and do get good MPGs. They have to be driven properly and at a sane speed.

Quote:

#5 COOL DOWN: Use exit ramps and truck stop access roads to cool your engine down before shutting it off. If you can coast in to a stop using very little fuel and keeping the exhaust temp down, there is no need to let the truck idle several minutes before shutting it off.

Myself and mechanics every where will major disagree with you on this one. Never and I do mean never shut down a hot engine with no idle time. I know what you are saying about light throttle into your fuel stop or other stop, but on a hot day this is no where close to enough turbo bearing cool down period. Shutting down while too hot cooks the oil in the turbo bearings and will kill your turbo quick. That 5 or 10 mins of idle cool down will sure seem cheap when faced with a premature turbo replacement.

Brickman · **^ Top** #53 4 Weeks Ago

Quote:

Originally Posted by MedicineMan

ya I have a cd here from cat on driving technics and they tell you to lug it down to 900 rpm

Quote:

Originally Posted by 550hpW900L

LOL i guess they want you to put new rods and mains in yearly. Also new U joints and bearings in the trans.

Quote:

Originally Posted by MedicineMan

it's funny. it even says "go ahead an let it run down, you won't hurt this motor!"

Even a C 15 pre bridge/Acert does not like to lug that low.

I have already came around a corner loaded on relatively flat ground or slightly up hill and picked it up from there but to lug it down that far on an uphill pull does not result in happy driving.

550hpW900L · **^ Top** #54 4 Weeks Ago

Very well said Brick!

550hpW900L · **^ Top** #55 4 Weeks Ago

Quote:

Originally Posted by Brickman

Even a C 15 pre bridge/Acert does not like to lug that low.

I have already came around a corner loaded on relatively flat ground or slightly up hill and picked it up from there but to lug it down that far on an uphill pull does not result in happy driving.

Yeah and couple that with a GINORMOUS turbo with lag down low and you got yourself a recipe for something breaking!

MedicineMan · **^ Top** #56 4 Weeks Ago

actually Brick COE's can be the most fuel efficient if done properly. Wind drag is dependant on total frontal surface area first and formost, then to a lessor degree the angle of that surface. You can have a big square coe with less frontal area (much less) the say a 379 pete. The main reason the fuel milage sucks on most coe trucks is that they were mainly around in the mechanical engine days.
Mabey you remember that really ugly coe peterbilt made for a few years in the 90's. it was real rounded and the front opened up like a sideways clamshell for servicing the engine. That truck with a trailer that had some aero treatments was capable of getting 10 or 11 mpg

maxeffort · **^ Top** #57 4 Weeks Ago

Quote:

Originally Posted by Brickman

Most of what was written is pretty good. But I've got to disagree with several points.

It has NOT been my experience that COE gets better MPGs, not even close.

Large car trucks even ones pulling a skate board can and do get good MPGs. They have to be driven properly and at a sane speed.

Myself and mechanics every where will major disagree with you on this one. Never and I do mean never shut down a hot engine with no idle time. I know what you are saying about light throttle into your fuel stop or other stop, but on a hot day this is no where close to enough turbo bearing cool down period. Shutting down while too hot cooks the oil in the turbo bearings and will kill your turbo quick. That 5 or 10 mins of idle cool down will sure seem cheap when faced with a premature turbo replacement.

If you basically coast in, It's not much different than idling, hence the reason for no or very little cooldown. The turbo will not cool any more than the idle exhaust temp, no matter how long you idle it.

So if you have a pyro and the exhaust temp was way down on the ramp, around the lot the turbo will not get much cooler if at all. Please if it makes you feel comfortable, be on the safe side 2-3 minutes is fine and won't use up much fuel.

Whole different story if you pulled a hill before stopping. You will need the five minutes for sure.

With any truck, set up has to right. As I wrote earlier, CAT made close to 11 mpg with a COE, but it was set up and driven properly.

Wind tunnel testing has shown that a COE is the best with a VAN trailer. May not be as good with a skatebord.

maxeffort · **^ Top** #58 4 Weeks Ago

Quote:

Originally Posted by Brickman

Even a C 15 pre bridge/Acert does not like to lug that low.

I have already came around a corner loaded on relatively flat ground or slightly up hill and picked it up from there but to lug it down that far on an uphill pull does not result in happy driving.

I think were on the same wavelength here. The very low RPM applies to cresting the hill. I don't think long continuous pulling below 1100 is a great idea. If you can crest at 1000rpm, it's not bad, rather than grab a gear at the crest. 900rpm is getting very low and pretty tough for the engine to recover.

maxeffort · **^ Top** #59 4 Weeks Ago

Quote:

Originally Posted by sano

Likewise, if you assume:
1) You run a constant 800 mile journey (at $1.30/mile)
2) You work 11 hours per business day, all year

Truck #1 goes 75mph and gets 5mpg will net about $64k
Truck #2 going 55mph and gets 7mpg will net about $92k.

Truck #2 will make 70 less trips, but the money saved overcomes the potential losses in work. Is my math correct? This seems like quite a bit of coin.

Math: [LINK POSTED BY MEMBER] Only Members Can View This Truck Forum Link. (comments appreciated)

Well done.

soon2betrucking · **^ Top** #60 4 Weeks Ago

Hey max, that is a really good way of explaining it, i hate engines, and when it comes to mechanics, i leave it to the mechanics, but i do what i have to do to make sure my baby never fails me

i have maneged to increase my mpgs from 6.2 upto 7.3 in a month,
i printed everything you said and i put it in my truck, and i read it, and then re-read and try my best to do everything you said, or when i go to our shop i take it in with me, and suggest he tries some of these tips on my truck, he now hates when i walk down there with papers in hand

but in the end, im usually the one to have the least problems with my truck

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