A few weeks ago, I wrote a blog titled “Answering the Question.” This was shortly after I managed to achieve 10 mpg lifetime average on the new Freightliner Cascadia Aero X. As normal, the 10 mpg sparked many questions in regards GVW, terrain and weather. The question of mountainous terrain and heavier GVW were answered in that blog.
With my typical cruise speed of 65 mph, another question asked often is what would my fuel mileage be at a higher speed? The last several days a pressing schedule allowed for the perfect opportunity to explore what my fuel mileage would be at higher speeds.
The test began in Oklahoma City, OK. My GVW was approximately 59,000 lbs. and my destination was Laredo, TX. A large portion of this route includes the speed limit being 75. I decided to take full advantage of this speed to see what results might occur. I refueled in Hillsboro, TX and the figures at the pump came in at 9.536. This is a nice number however part of this fill up included a 65 mph cruising speed. I then continued onto Laredo and was unloaded and reloaded to a GVW of approximately 72,000 lbs. After leaving Laredo and heading towards Charlotte, NC I used routes I-35, I-10, I-12, I-10, I-65 and I-85 refueling at Shorter, AL. The results as figured at the pump were 8.96 mpg. From Shorter, AL continued on I-85 to I-285 to I-85 to US 321 to I-40. Next, I proceeded to Statesville, NC to go home for the weekend and on Monday I traveled down I-77 to deliver to Charlotte, NC. I unloaded and reloaded for my return trip to Laredo, TX. I call this the north half of my route which includes any 70 mph speed limit which once again, I fully took advantage of. I stopped and refueled in Slidell, LA using the same previous routes. The results at the pump were 9.25 mpg. I then continued onto Laredo, TX. A large portion of the speed limits were up to 70 until I reached Texas where 75 mph became more predominate. I loaded and reloaded in Laredo, TX. My GVW at this point was approximately 69,000 lbs. Upon leaving Laredo to head back to Charlotte, the need for speed has subsided. I lowered my max cruise speed to 70 mph. I began my trip back to Charlotte, NC using the same previous routes, stopping in Hammond, LA to refuel the truck. The results at the pump came in at 8.62.
My takeaway from traveling at higher speeds was that it was interesting, time effective and much more stressful. I had a chance to witness the combination of results from the outstanding Cascadia Aero X combined with the Detroit integrated drive train along with my Nose Cone equipped, Fleet Engineer Side Skirts, Flow Below wheel covers and Stemco Trailer Tail all working in unison to minimize aerodynamic drag at higher cruising speeds. Rolling resistance was also a factor which was negated by the Michelin wide base single tires . In the past, cruising speeds such as this would have never yielded the fuel mileage results listed above. The downside to all of this and the mountain testing I conducted a few weeks ago has reduced my overall lifetime average at 39,000 miles down to 9.8 mpg. Now it’s time to get back to work and increase that number back up to 10 mpg .