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Fuel Economy with a Ford Diesel - Every Bit of Fuel Savings Adds Up!The picture below shows a Ford E350 diesel powered van. Just to give you an idea on the type of fuel economy on this Ford diesel rig, it was purchased used out of state and driven home cross country and fuel usage carefully measured. On the return trip at mostly highway speeds, the fuel economy of the Ford diesel 7.3L Power Stroke engine was around 18 mpg. Later, this van was modified to run dually rear tires. After this change, the highway fuel economy dropped to around 16 mpg. It appears that the extra rolling resistance of the additional 2 tires might have lowered the fuel economy of this Ford diesel. In addition, the aerodynamics of the van (whatever little aerodynamics it had) might have been reduced further by adding the duallies, since the extra tires stick out the sides of the van.
Ford 7.3 Power Stroke Diesel Dually Van The 7.3L Power Stroke was a great engine, but as is often the case, progress moves things forward and results in changes. The venerable 7.3 was phased out in the 2003 model year, and the Power Stroke 6.0 engine took over. Unfortunately, the 6.0 engine was never as good as the 7.3. After a few years, the 6.0L was replaced by the Power Stroke 6.4L turbo diesel engine. More recently, Ford came out with it's own diesel engine design, and this Ford 6.7L engine is supposed to have some improvements over it's predecessors. One of the areas of improvement is supposed to be in terms of fuel efficiency. In terms of the Ford E-350 van fuel economy, another factor could have been that the size of tires selected for the dually conversion had a slightly smaller overall diameter than the stock tires. All this combined with the very low 4.10 rear axle gears made for less than optimal fuel economy. However, one winter a set of snow tires were put on back of this van. Not dually, but just a single set of snow tires. In this case, the snow tire size chosen was bigger than the original stock tires. As a result, the diameter of the tires and the overall gearing of the van was increased over stock. This higher gearing combined with the single tires out back really helped improve fuel economy. Instead of getting 16-17 mpg while highway driving, the fuel economy of this Ford diesel jumped up to 20 mpg. Pretty good considering the size of this van. That was the first time this particular Ford diesel van cracked the 20 mpg fuel economy level.
High Flow 4" Exhaust System A bigger exhaust system was also installed on this van. The Diamond Eye exhaust was a full 4" all the way from the turbo to the exhaust tip. Since this van did not come with any catalytic converter, particulate filter, or other emissions related exhaust equipment, it was relatively easy to make the exhaust change. The bigger exhaust did improve fuel economy around 1-2 mpg overall; however, the additional noise (especially at highway speeds) was very annoying. Eventually, the stock exhaust was put back on in favor of a little quieter driving conditions. The diesel engine is still far from quiet, but at least the resonating drone was gone when switching back to the original exhaust. It has been said that the noise is not as much of an issue on a truck since the cab is up front and the exhaust runs under the bed and exits out back far behind where the passengers sit. On the other hand, with the van, the exhaust runs the full length of the passenger compartment and it seems to transfer more of its noise to the interior. In addition to the exhaust, a tuner module was added that gave some different tuning options. There was a setting for towing, some settings for performance gains (+ 100 HP!), and also a fuel economy tune. This economy setting was supposed to change the fuel injection timing to help improve combustion efficiency. In addition, this economy tune setting also changed the shift pattern of the automatic transmission. Basically, it shifted up sooner and was slower to downshift to keep the tranny in a higher gear more often. This helped keep the engine RPM's lower which in turn should lead to better fuel economy. In theory, this is all true. In reality, there was no big difference in fuel economy while using the economy tuner setting. Perhaps it was because even in the economy setting the tuner added more power, and it was hard to drive it without tapping into that extra power more often. In other words, with the extra power on tap, it was easy (more fun) to accelerate harder rather than driving more conservatively. In the end, the best fuel economy for this Ford diesel van was right around 20 mpg (driving like a grandpa). Usually, it was closer to 18 mpg for highway driving. A big part of this limit is probably the 4.10 gears. With an axle with taller 3.55 gears, it would probably be possible to see better fuel economy on a Ford diesel. Then again, with the higher gear ratio, you will also be limited with the amount of weight that you can safely tow. There's always a tradeoff. Back to the topic of the fuel economy of the newer Ford diesel trucks. For those of you interested in the fuel economy of some of the newer Ford F-350 diesel trucks, then you might be interested in the below showing how the Ford 6.7L diesel engine compares to the Dodge and Chevy diesel trucks in terms of fuel economy. This 6.7L diesel engine was designed by Ford and puts an end to the longstanding use of the International designed and built Power Stroke engine used in the older Ford trucks. The fuel economy of the Ford 6.7L diesel engine looks to be impressive.
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Fuel Economy - Ford Diesel
