Clean, Strong, and Quiet
In the last few years, every domestic pickup manufacturer has upped its V-8 diesel displacement, and Ford's entry is now competitive with its brethren. At 6.4 liters (390.5 cubic inches), the new Power Stroke engine that replaces the previous 6.0-liter offering is smaller than the new Dodge Cummins 6.7- and GM Duramax 6.6-liters, but they're all within similar horsepower and torque ranges. The GM diesel has a marginal lead at 360 horsepower, but the Dodge and Ford are right there at 350. All three offer 650 pound-feet of torque.

The 6.4-liter Ford diesel's iron block is capped with cast-iron heads that breathe through four valves per cylinder. A high-pressure common-rail injection system delivers fuel to piezo-electric injectors, which offer larger volumes of fuel quicker than with solenoid injectors. That system, along with laminated steel valve covers that muffle much of the pinging and raspiness typical of diesels, also makes Ford's most powerful pickup diesel its quietest. A pair of turbochargers provide boost at different rpm ranges--a smaller one spools up quickly to offer boost from off-idle for near-immediate response and reduced lag, and the larger one follows with a lower-pressure charge to carry the V-8 through its horsepower and torque peaks.

This powerplant generates a lot of heat, so the engineers compensated with a cooling system originally designed for F-550 chassis-cab trucks. The largest of the six radiators, which offers nearly 20 percent more frontal surface area than the previous F-Series radiator, is fed by a water pump that puts out 50-percent-greater flow. In addition, the pistons are sprayed with jets of cooling oil through special galleries to reduce combustion temperatures as part of the emissions system, which also includes an oxidation catalyst and a particulate filter in the exhaust sequence. Together with the use of ultralow-sulfur diesel fuel and exhaust-gas recirculation, which puts burned gases through additional cooling before they're put back into the air system, the engine burns as cleanly as a gas V-8 and is almost totally devoid of soot. The gas 5.4-liter V-8 and 6.8-liter V-10, which were new in 2005, remain unchanged for 2008.--S.C.

Tow Rating Details
The lowest factory tow rating for any new Super Duty is 8100 pounds, for a single-rear-wheel 4WD Crew Cab with the 5.4-liter V-8, 3.73:1 gears, and a manual transmission; the automatic version ups that number to 9100. The numbers in the chart are maximums and assume a low-option truck with driver, otherwise GCWR will likely be exceeded.

For conventional trailers, any 2WD or 4WD single-rear-wheel truck can pull 12,500 pounds with the V-10 or diesel regardless of axle ratio or transmission. A dualie F-350 rates up to 15,000 for most applications, with the diesel or a V-10 running 4.30:1 gears, and the F-450 (only available as a diesel Crew Cab) rates at 16,000 pounds.

Fifth-wheel/gooseneck ratings vary substantially, so only the maximum is given in the chart. Note that it may be possible to exceed a single-rear-wheel truck's GVWR or rear-axle rating without exceeding GCWR because of high hitch-pin weight. Ratings generally dip 200-300 pounds per step up in cab size, and the highest ratings are all with automatic transmissions.--G.R. Whale

Maximum Tow Rating by Model
F-25016,100 15,700 Reg cab, diesel, 3.73:1 axle
F-350 SRW16,800 16,300 Reg cab, V-10, automatic, 4.30:1 axle
F-350 DRW18,700 18,200 Reg cab, diesel, auto, 4.30:1 axle, Tow Boss pkg
F-45024,500 24,000 Automatic, 4.88:1 axle, Hi-capacity trailer pkg
MaxIMUM Tow Rating @ GVWR*
F-25023,000 8800-10,000 13,000
F-350 SRW23,000 10,100-11,500 11,800 (2WD only)
F-350 DRW26,000 11,800-13,000 13,000
F-45033,000 14,500 18,500
*passengers, cargo and pin weight