The cost of diesel fuel has resulted in severe penalties to both owner/operators and fleets in their day-to-day operating budgets.

In the September issue of Truck News I discussed the fact that the search for fuel economy or performance is basically a compromise.

We looked at some of the pros and cons of “direct” versus “overdrive” transmissions and their contribution to a gear-fast, run-slow concept and how fuel economy can be affected.

However, there are other areas outside of the regular preventive maintenance checks that need to be factored into the fuel economy equation:

A coast-down test can usually indicate if one vehicle has an advantage due to its aerodynamics package, types of tires, driveline efficiency or dragging brakes.

With every mph increase in vehicle speed, an industry estimate is that you will suffer a two per cent penalty in fuel consumption.

Employing aerodynamics on the tractor cab, such as air deflectors, fairings and a bumper dam, can improve your tractor’s fuel economy by between 10 and 15 per cent

A tandem axle configuration will generally use approximately 1.5 per cent more fuel than will a single axle design. Extra axles require more power, even if they are non-driving types.

Tire pressures… it is estimated that tires 10 psi/69 kPa underinflated will cost you another one per cent fuel penalty.

Tire matching is critical, and dual tires must have equal diameters since smaller tires will scuff. Few truckers today use bias-ply models, since radial tires offer an eight to 10 per cent fuel economy improvement, while low profile models can provide between a three to four per cent improvement over standard radials.

Incorrect wheel alignment can significantly affect fuel economy. Regularly inspect tires for unusual wear as well as steering complaints.

Trailer design is important since pulling a ribbed model will cost you an extra one per cent on your fuel bill.

Square corner trailers versus smooth models can cost you up to four per cent more in fuel penalties.

Pulling double trailers versus a single can result in up to a 7 per cent fuel penalty.

About 1.5 per cent less fuel will be used if the trailer height is reduced from 13.5 feet to 13 feet (but only if there is no air deflector on the tractor).

Up to a 3 per cent improvement in fuel consumption can be realised through selecting the proper engine oil for your route.

A reduction of 1.5 per cent in total fuel consumption can occur if the correct gear oils are employed.

Intake and exhaust restriction… you will suffer an approximately one per cent penalty in fuel consumption for a 20-inch water intake restriction and a one percent more for a two-inch mercury exhaust restriction.

A 1 per cent penalty in fuel consumption will occur due to the power draw off the air compressor when pumping. Air line leaks and un-necessary braking can also result in excessive operation of the air compressor. Electronic engines equipped with an electronic air-compressor governor action help reduce air compressor draw and will improve fuel economy.

In warmer weather, using the air-conditioner can cost you a three per cent fuel penalty plus an additional six per cent penalty if the coolant clutch fan is triggered due to a greater cooling system heat load.

The power steering pump load can increase fuel consumption by one per cent during turns.

Heavy electrical loads on the alternator can cause a 1 per cent fuel

consumption penalty.

Temperature controlled cooling fans are only required approximately three to five per cent of the time; when the fan is driven, it will typically draw about five per cent of the engine horsepower, or approximately 15 hp on a 350 to 400hp engine when driven flat out.

Driver efficiency resulting from individual technique plays a role. A good professional driver can account for as much as a 25 per cent savings in fuel economy.

Accurate fuel measurement and records must be maintained to determine fuel economy.

Every 1000 lb. added to the load will decrease fuel economy by about 0.5 per cent, depending on weather and road conditions.

Excessive idling can cost you between 900 and 1200 gal./year, so shut it down whenever possible.

Weather conditions and winds, according to SAE Type 11 tests, can account for up to a 17 per cent variation in fuel consumption for a given vehicle.

By paying attention to just some of these tips, you can get a greater return on every dollar of liquid gold you buy. There are three additional issues now receiving much more emphasis around the industry. These also should be factored in and considered when you look to improve your fuel ecomony:

This is an area several research agencies and OEM’s are tackling head-on at this time. Trailers have not kept pace with the streamlining of tractors.

Reports indicate that trailer streamlining can result in a fuel savings of four to six per cent annually, along with improved handling of the trailer. And the idea could extend steer tire life by between 25

and 40 per cent.

Bandag recently introduced FuelTech retread model tires that claim to provide up to 1.6 per cent better fuel performance than the best in-class new tires without sacrificing treadwear or traction.

The use of Non-Aqueous Propylene Glycol (NPG) as a coolant for heavy-duty diesel engines is gaining momentum.

NPG antifreeze and coolant system conditioner can offer you lower cost levels of regular maintenance. Typically, a 1 per cent penalty in fuel consumption is noted for each 10F reduction below a standard 185F coolant operating temperature.

Taken together, these three areas will result in improved fuel economy gains on a yearly basis to help you reduce your overhead running costs. And that’s what it’s all about, isn’t it. n

– Bob Brady is the president of Hitech Consulting in Burnaby, B.C.