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This Is The Beginning Of What's Sure To Be a decade of huge changes in the automotive landscape. Soaring oil prices and growing concerns about global warming are prompting the government to enact ever-stricter regulations in the areas of fuel economy and emissions. Those regulations are pushing automakers to find cleaner and more efficient ways to power our vehicles.

Bringing up the curtain on this new age of efficiency was the EPA's mandate to replace conventional diesel fuel with ultra-low-sulfur diesel (ULSD) as a means of reducing diesel emissions. It's a rolling change that will take several years to fully implement, but automakers and truckmakers were among the first to feel its effects when they were asked to deliver ULSD-burning vehicles to market by January 1, 2007. This meant Chrysler, Ford, and GM had to redesign or revamp the diesel engines for their heavy-duty pickups to meet that deadline. In essence, the world of diesel-powered haulers changed almost overnight.

We can't remember when (or if) an entire truck segment went through this kind of change all at once, and it seemed like the perfect opportunity for a comparison test of the new diesels. But what kind of test? We discussed including them in our annual 4x4 of the Year competition, but soon realized that test is too trail-oriented to truly evaluate these trucks' attributes. No, this called for something different, a test that borrows some of the 4x4 of the Year's structure but takes place on the kinds of terrain that would typically be encountered by big diesel 4x4 haulers.

What we came up with is a comparison test to approximate what a truck owner would experience if he or she bought a diesel pickup to tow a trail rig. We planned driving routes in some of the toughest tow country in our neck of the woods: the highways and two-lanes in the hills around the Tejon Pass, better known as the Grapevine. What's so tough about it? Well, for starters, there's the altitude. Most of our testing took place between 3,000 feet and the 4,144-foot summit. There's very little flat ground south of the Pass, so the constant up- and downhill driving would test power delivery and braking ability alike. Also, there's always a huge amount of traffic flowing through this area (it's the major north-south artery linking Southern California with the rest of the state), so merging with traffic would test not only vehicle power but also visibility. And finally, nestled in these hills is the Hungry Valley SVRA, where we could put these rigs on graded dirt roads and trails to simulate travel to a trail head.

We worked hard to keep this test as apples-to-apples as possible. We asked the manufacturers for similarly equipped trucks-all '08-model 1-ton, crew-cab, dual-rear-wheel, 4x4 diesels equipped with the maker's towing packages-and we're proud to say that we're the only magazine that assembled such a fleet. (Other magazines that have printed similar tests did so with a mix of single- and dual-rear-wheel trucks.) During our back-to-back evaluations, all three trucks traveled the same roads and trails on the same days, with testdrivers switching among them to drive and then recording their impressions in notebooks. To keep the towing comparisons consistent, each truck towed the same piece of equipment: our Ultimate Adventure Jeep Wrangler lashed to a flatbed trailer. The 9,800-pound load was heavy enough to test tow capabilities without surpassing any of the trucks' tow capacities.

When it came time to rank the contestants, the judges (Ali Mansour, Fred Williams, and yours truly) scored each truck in a number of categories using a 0-5 scale, with 0 being hateful and 5 being best. We allowed more than one truck to get the same score in a category (if all three were equally quiet at idle, for example, they could all score 5s), which resulted in tie scores in some individual categories.

When all the votes were in, however, there was no tie. One truck won enough categories outright and scored highly enough in the others to claim victory. Read on to see which of the new, clean-diesel pickups earned our first Ultimate Tow Rig title.