You don't have to drive a nerdy gasoline hybrid car to get good fuel mileage. You can maximize the miles per gallon achieved in a fullsize truck with a few flicks of a pen when you order a turbodiesel at the dealership. To test our theories, we ordered a two-wheel-drive Chevy Silverado 2500HD with the 6.6L Duramax engine and the Allison six-speed automatic transmission. For model year 2006 General Motors has improved the efficiency of the Duramax engine while increasing the power output. Engines with the LBZ order code make 360 horsepower and 650 lb-ft of torque. With a new, stronger engine block and a lower compression ratio, the Duramax is said to be the diesel fuel economy champ among the Big Three automakers when it is combined with the six-speed Allison automatic transmission. For model year 2006 General Motors has improved the efficiency of the Duramax engine while This is where the rubber literally meets the road in the fullsize fuel economy discussion. The choices you make when ordering wheels and tires can make a big difference in how many miles you get for each gallon of fuel used. The key to economy is having a low resistance to rolling, so we ordered street tires that do not fight the asphalt nearly as much as mud terrains or all terrains. Obviously, single-rear-wheel trucks have less rubber-to-road contact than dualies, so we went with an SRW 2500HD. Aluminum wheels are lighter, so there is less rotational mass at each corner of the truck, which should help our mileage figures. General Motors only offers the 3.73 axle ratio with the Duramax, but you should choose the highest axle ratio to optimize the final drive ratio in your truck. This is where the rubber literally meets the road in the fullsize fuel economy discussion. As you can see, we chose a two-wheel-drive truck. In addition to saving weight, our truck did not have to waste energy turning CV shafts or front differential parts. We ordered an option package (LT2) that included front fog lamps because the trucks without this option have large air-grabbing indentations where the lights should be. Plugging these and any holes in the air dam will reduce the amount of wind resistance at the front of the truck. As you can see, we chose a two-wheel-drive truck. In addition to saving weight, our truck Since we were attempting to get the best mileage, towing a trailer was out of the question. That allowed us to order the standard rearview mirrors and avoid the extending tow mirrors that reduce the aerodynamics of the Silverado. Since we were attempting to get the best mileage, towing a trailer was out of the question Transmission TruthsThe Allison transmission has just as many speeds as the manual. Plus, it has higher overdrive gear ratios. The double-overdrive feature allows the Duramax to loaf along-even at highway speeds. ModelZF S6-650 (ML6)Allison 1000 (MW7)Type6-speed manual 6-speed automatic Gear Ratios 1st 5.79 3.10 2nd 3.31 1.81 3rd 2.10 1.41 4th 1.31 1.00 5th 1.00 0.71 6th 0.76 0.61 Reverse 5.23 4.49 Rear Axle 3.73 3.73 SOURCES Chevrolet « | 1 | 2 | View Full Article Enjoyed this Post? Subscribe to our RSS Feed, or use your favorite social media to recommend us to friends and colleagues!