Dodge Cummins Diesel Forum - View Single Post

slowmover · 11-17-2010, 06:48 PM

Keep a record of all gallons used. Fuel economy is the average of that. Single highs -- even repeated highs (or lows) are meaningless by comparison -- it is the TOTAL amount of fuel burned for the work done. (See sig) Until your records show fuel use over thousands of miles (or one year, better) you won't actually know what you OR the truck is capable of. Generally, the truck is better than the driver. You work for the truck, not the other way around. If you don't, fuel mileage will be poor for your trucks configuration.

Once a truck is spec'd (built) then fuel economy comes down to aerodynamics and gearing (given low rolling resistance tires), AND the way it is operated to maximize these two factors:

The #1 factor in getting better fuel mileage is to REDUCE HORSEPOWER DEMAND.

This is a combination of vehicle configuration, condition, load and DRIVER OPERATION.

Keep your pyrometer under 600°F and keep your boost pressure under 5 PSI when solo.

The #2 factor in getting better fuel mileage is to
AVOID RUNNING THE ENGINE WHEN YOU ARE NOT MOVING.

If you want to spend money, avoid tuners, exhaust, CAI, etc. Get a manifold pressure gauge and an exhaust temperature gauge and learn to use them to benefit mileage.

According to Peterbilt Engineering Systems Manager Rick Mihelic, the truck engine must overcome five primary forces in order to move the truck down the road. They are:

• Rolling resistance, or the loss due to friction between the tires and the road;

• Mechanical losses, which result from friction inside the engine and the drivetrain;

• Accessory losses, which result from running alternators, air conditioners, fans, etc.;

• Grades, or changes in road elevation; and

• Aerodynamic drag.

The chief impediment to fuel mileage under 50 mph is the tires. The best tires for fuel economy (and longest life) are the stock MICHELIN LTX A/S. (I may get 250k out of the first two sets at present rate of wear). Use factory inflation guidelines (and a certifed scale) to dial in pressure. Off-road tread or oversize, etc, really hurt mpg.

At above 60 mph is the problem is rolling resistance now compounded by aerodynamic resistance. I run the roads at 58 mph . . on a 300-mile trip the difference is not even .5/hour (and you'll spend more time with the channel changer that same day . . which has the greater value?). At this speed I can just plunk on the cruise and let the Cummins torque me over every hill (unless I'm in West Virginia). Extrapolated over many tanks and the benefits are obvious: the driver is more rested in all instances, the peripheral vision is FAR better, and the truck is subjected to less wear for the miles covered in re engine, tires, brakes, fluids, etc. Don't treat the truck as being disposable, ever.

I also find that for trip planning purposes that this constant road speed does not need to change on cross-country trips for big metro areas. No lane changes. No traffic braking. It's marginal stuff, but it all adds up. I know in advance where all my stops will be (that's trip planning: on time and in place according to the clock [have been a truck driver]) so as to keep distractions to a minimum. Need to get there faster? Leave earlier. Spend some time with mapping software to see if a few more miles on the big road beats stop-n-go traffic. With these heavy trucks it usually does. I think nothing of going several miles "out-of-the-way" (OOR, or, Out of Route) to avoid stop and start.

Simply said I never turn the key that I haven't already mentally mapped out my route. And I try to avoid EVER starting the truck unless I will drive 30-miles as it takes at least that long for all fluids, greases, tires, etc to come up to the warmest, lowes-friction point. Really, tires don't reach a steady, non-varying state until 1.5 hours into a constant speed trip. So I tend to use freeways to take me to the furthest point and then work my way back to the house. Were I a commuter I'd be more likely to use the block heater and maybe an ESPAR to pre-warm the truck to bring op temps up quickly.

Don't idle to warm up. As soon as oil pressure is constant ease away from the curb. I run the first few miles at 18-1900 rpm on city streets (33 mph in a 40 zone) as usual. The Cummins likes this rpm range for mpg. Idling just wastes diesel AND wears down the motor. In a cold climate (below 40F) use other means to extract the most work from the fuel. The up-front cost is more than offset over the life of the vehicle if it can be used daily.

Rich Taylor -- GMC Truck Division guru -- says that a grille-block, partial bellypan, and tonneau are good for pickup truck fuel economy.

As with aftermarket go-fast, wear-out-the-truck-faster toys, a lift kit is murder on fuel mileage, ruins handling/braking dynamics, and makes a truly lousy tow vehicle. Keep stock, or as close to stock as possible with the addition of a bed cover or very close fitting bed topper.

Commercially produced aerodynamic pickup bed cap (see other threads on homebuilt versions; great reading)

Commercially produced aerodynamic pickup bed cap - Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com

I would include rigorous maintenance. I like to do oil changes at 6-mos/6000 and include changing the air & fuel filters along with the oil & filter. I changed to ROTELLA 5W-40 synthetic as the motor turned over easier than with ROTELLA 15W-40 conventional. (The best oil would be the true, fully synthetic MOBIL DELVAC 5W-40). Stick with BALDWIN, DONALDSON or FLEETGUARD filters (and new factory part number air filter). Keep the tank topped off and occasionally run some STANADYNE thru it. Stay on top of -- keep ahead of -- maintenance intervals. Don't be cheap about supplies, tools or equipment to this end. A guy who is serious about fuel mileage will build a garage to house the truck . . . never thought of it that way, did you? Equipment kept out of the elements will last longer.

Fuel economy is just one indicator of operating/ownership costs and not the most important. The longest lasting truck with the lowest cost-per-mile is the true economy champ.

Good luck

.

11-17-2010, 06:48 PM	#4 (permalink)
slowmover Diesel Freak Join Date: May 2009 Location: Corpus Christi, Texas Posts: 889 Thanks: 128 Thanked 101 Times in 72 Posts slowmover's Truck Pics	Keep a record of all gallons used. Fuel economy is the average of that. Single highs -- even repeated highs (or lows) are meaningless by comparison -- it is the TOTAL amount of fuel burned for the work done. (See sig) Until your records show fuel use over thousands of miles (or one year, better) you won't actually know what you OR the truck is capable of. Generally, the truck is better than the driver. You work for the truck, not the other way around. If you don't, fuel mileage will be poor for your trucks configuration. Once a truck is spec'd (built) then fuel economy comes down to aerodynamics and gearing (given low rolling resistance tires), AND the way it is operated to maximize these two factors: The #1 factor in getting better fuel mileage is to REDUCE HORSEPOWER DEMAND. This is a combination of vehicle configuration, condition, load and DRIVER OPERATION. Keep your pyrometer under 600°F and keep your boost pressure under 5 PSI when solo. The #2 factor in getting better fuel mileage is to AVOID RUNNING THE ENGINE WHEN YOU ARE NOT MOVING. If you want to spend money, avoid tuners, exhaust, CAI, etc. Get a manifold pressure gauge and an exhaust temperature gauge and learn to use them to benefit mileage. According to Peterbilt Engineering Systems Manager Rick Mihelic, the truck engine must overcome five primary forces in order to move the truck down the road. They are: • Rolling resistance, or the loss due to friction between the tires and the road; • Mechanical losses, which result from friction inside the engine and the drivetrain; • Accessory losses, which result from running alternators, air conditioners, fans, etc.; • Grades, or changes in road elevation; and • Aerodynamic drag. The chief impediment to fuel mileage under 50 mph is the tires. The best tires for fuel economy (and longest life) are the stock MICHELIN LTX A/S. (I may get 250k out of the first two sets at present rate of wear). Use factory inflation guidelines (and a certifed scale) to dial in pressure. Off-road tread or oversize, etc, really hurt mpg. At above 60 mph is the problem is rolling resistance now compounded by aerodynamic resistance. I run the roads at 58 mph . . on a 300-mile trip the difference is not even .5/hour (and you'll spend more time with the channel changer that same day . . which has the greater value?). At this speed I can just plunk on the cruise and let the Cummins torque me over every hill (unless I'm in West Virginia). Extrapolated over many tanks and the benefits are obvious: the driver is more rested in all instances, the peripheral vision is FAR better, and the truck is subjected to less wear for the miles covered in re engine, tires, brakes, fluids, etc. Don't treat the truck as being disposable, ever. I also find that for trip planning purposes that this constant road speed does not need to change on cross-country trips for big metro areas. No lane changes. No traffic braking. It's marginal stuff, but it all adds up. I know in advance where all my stops will be (that's trip planning: on time and in place according to the clock [have been a truck driver]) so as to keep distractions to a minimum. Need to get there faster? Leave earlier. Spend some time with mapping software to see if a few more miles on the big road beats stop-n-go traffic. With these heavy trucks it usually does. I think nothing of going several miles "out-of-the-way" (OOR, or, Out of Route) to avoid stop and start. Simply said I never turn the key that I haven't already mentally mapped out my route. And I try to avoid EVER starting the truck unless I will drive 30-miles as it takes at least that long for all fluids, greases, tires, etc to come up to the warmest, lowes-friction point. Really, tires don't reach a steady, non-varying state until 1.5 hours into a constant speed trip. So I tend to use freeways to take me to the furthest point and then work my way back to the house. Were I a commuter I'd be more likely to use the block heater and maybe an ESPAR to pre-warm the truck to bring op temps up quickly. Don't idle to warm up. As soon as oil pressure is constant ease away from the curb. I run the first few miles at 18-1900 rpm on city streets (33 mph in a 40 zone) as usual. The Cummins likes this rpm range for mpg. Idling just wastes diesel AND wears down the motor. In a cold climate (below 40F) use other means to extract the most work from the fuel. The up-front cost is more than offset over the life of the vehicle if it can be used daily. *Rich Taylor -- GMC Truck Division guru -- says that a grille-block, partial bellypan, and tonneau are good for pickup truck fuel economy.* As with aftermarket go-fast, wear-out-the-truck-faster toys, a lift kit is murder on fuel mileage, ruins handling/braking dynamics, and makes a truly lousy tow vehicle. Keep stock, or as close to stock as possible with the addition of a bed cover or very close fitting bed topper. Commercially produced aerodynamic pickup bed cap (see other threads on homebuilt versions; great reading) Commercially produced aerodynamic pickup bed cap - Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com I would include rigorous maintenance. I like to do oil changes at 6-mos/6000 and include changing the air & fuel filters along with the oil & filter. I changed to ROTELLA 5W-40 synthetic as the motor turned over easier than with ROTELLA 15W-40 conventional. (The best oil would be the true, fully synthetic MOBIL DELVAC 5W-40). Stick with BALDWIN, DONALDSON or FLEETGUARD filters (and new factory part number air filter). Keep the tank topped off and occasionally run some STANADYNE thru it. Stay on top of -- keep ahead of -- maintenance intervals. Don't be cheap about supplies, tools or equipment to this end. A guy who is serious about fuel mileage will build a garage to house the truck . . . never thought of it that way, did you? Equipment kept out of the elements will last longer. Fuel economy is just one indicator of operating/ownership costs and not the most important. The longest lasting truck with the lowest cost-per-mile is the true economy champ. Good luck . __________________ 2004.0 DODGE Ram QC/LB 2500 2WD/6-speed Cummins 305/555 ISB. 7,360-lb. Stock. 180,000 miles at 4,625-hrs @ 39-mph average. 15-cpm solo & 25-cpm towing; 22-mpg average* past 37k-miles* Last edited by slowmover; 11-17-2010 at 11:46 PM.