Soon after driving their brand-new truck off the lot, expediters Bob and Linda Caffee found they were getting 6.7 miles per gallon. That's when they "got religion" about fuel economy.

Bob says, “After two weeks we figured out we could not afford to run this truck at the speed limit. That’s when we slowed down to driving about 57 mph. That got us up to about 7.5 mpg. Then we started trying to find more things we could do to get better fuel mileage.”

Their search was not in vain. They drive the same truck today and now enjoy 10.5 mpg — a 3.8 mpg improvement. When asked why fuel savings were so important to the Caffee’s, Bob’s answer was simple, “The more you can save on fuel, the more you can put in your pocket.”

The man has a point. At $3.00 a gallon and the 148,000 miles a year the Caffee’s drive, a 3.8 mpg increase in fuel economy translates into almost $24,000 per year. That’s some serious pocket money.

The truck is a Freightliner M2 Business Class model with a 300 horsepower Cat C7 engine and a five-speed, fully-automatic Allison transmission. It is a straight-truck designed to haul expedited freight. The Caffee’s have made a number of changes to the truck to get to 10.5 mpg. Some of the changes were intentional, others just worked out for the good.

The first thing the Caffee’s did was slow down. Bob says, “The beauty of that is everyone can do it. It does not cost a dime to do. Running at 57 mph, we have never been late for a pickup or delivery. The key is staying in the truck, keeping the doors shut and keeping the truck moving. If you have to stop, stop, but don’t make unnecessary stops at truck stops and rest areas. Accelerating the truck to get back up to speed uses fuel.”

Bob adds that PrePass minimizes stops at scales and E-ZPass eliminates complete stops at many toll booths. About driving slower, Bob says, “Our carrier uses 45 mph to plan a trip, which gives us plenty of time even at 57 mph.”

After slowing down and minimizing stops, the Caffee’s turned their attention to the truck and fuel-saving devices. They installed AirTabs™, changed their transmission from five speeds to six and experimented with fuel brands. That cut their fuel consumption by another 0.5 mpg. Because the changes were made at roughly the same time, the Caffee’s cannot say what portion of the improvement comes from each change.

Bob said some of the improvement that was found by changing fuel brands went away. Fuel blends change from time to time so a committing to one brand may work for a while but not work later on.

AirTabs™ are devices that attach to the outside walls of a straight truck or semi trailer, near the rear doors. They reduce aerodynamic drag by changing how the air flows around the truck. The transmission change from five speeds to six was done making a $100 change in the truck’s computer programming. Bob says the transmission change lowered their 57 mph engine rpm from 1,950 to 1,550.

The Caffee’s tried using a fuel conditioner for a while and saw a 0.3 mpg improvement. They no longer use it because the cost roughly equals the benefit. It was also a chore to buy it cases at a time for the discounted price and then carry it in the truck until it is used.

In June, 2007, the Caffee’s made another change to their truck, an expensive one. They replaced their original rear tires and wheels with wide-singles. One wide-single tire costs less than the two traditional tires it replaces. The extra expense came from the new wheels needed for the tires.

They are just now beginning to see an mpg improvement from the tires. If the Caffee’s had it do over again, they would buy not the high-torque, deep-lug wide-single tire, but one with less original tread depth that is designed for fuel economy. The difference is in how the lugs flex, Bob says. Deeper lugs flex more, which increases rolling resistance and reduces fuel economy. With 200,000 miles and 17/32″ tread depth now on the tires, they are worn to the point where fuel savings can be noticed.

Bob also reports a “huge difference” in how the truck’s ride improved with wide-single tires. When driving the truck home after getting the wide-single tires installed, he noticed the usual front-wheel bumps but was pleasantly surprised to not feel the same bumps with the back wheels like he did before.

The next change made to the truck was the addition of a TURBO 3000D. According to the manufacturer’s web site, “The TURBO 3000D works to improve [fuel] atomization by creating a change in the travel pattern of the fuel, prior to the fuel injector.” Bob installed it himself and immediately noticed that the engine ran smoother. But the jury is still out on fuel economy improvement because of a problem with the truck.

For several months, the Caffee’s had a sense that the truck was not running quite right. When they started having intermittent engine power issues, they took it to the shop, but when they did, the truck would run fine. ECM codes were found but mechanics were at a loss to say what caused them. That happened five times before the truck finally broke down and stayed that way. The injection pump was replaced, which not only got the truck running again, but also made a full 1 mpg improvement in fuel economy.

The next change made to the truck was low-tech. The Caffee’s removed their outside sun visor and instantly noticed a 0.3 mpg improvement. The fuel economy gain produced no comfort or vision loss when driving toward the sun. The inside sun visors block out the sun as they did before.

Still working on maximizing their mpg, Bob was installing a FASS Fuel System (fuel air separation system) when Expedite NOW interviewed him. While the Caffee’s have no FASS Fuel System results to report now, it is clear that their relentless pursuit of fuel economy improvements has paid off.