My view ...

The private blog of Andy Prevost. My experiences, my words. On any topic ...
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More on fuel economy ...

My first truck was a 1969 GMC pickup truck. I think the year I bought that was around 1976 or 1977. I owned a body shop and garage at the time, and the truck was supposed to be for car parts, tires rims, body panels, and supporting customers. 

The GMC was a piece of junk. While it was only 7 or 8 years old, it was a rust bucket barely worth putting any effort into saving. It was just a work beast and nothing more. I never really worried much about gas mileage in this beast, it was only a six cylinder work truck.

Skip ahead a few years and my next truck was a 1999 Ford Ranger. All my trucks starting with this one have been 4X4. No particular purpose, none are for work, all were for projects. Projects to keep my mind off of health issues. 

The 1999 Ford Ranger didn't stay with me too long. I sold it fairly quickly and replaced it with a 2000 Ford Ranger. Not really what I wanted long term, so it was sold off fairly quickly and replaced with "the dream" truck ... a 2003 Ford Ranger XLT FX4. The FX4 was a beauty showing minimal rust but a lot of mileage – over 360K. My health wasn't that great, and this truck seemed to fit the bill of a light amount of work. Enough to keep me busy and active. Turned out that was an under-estimate of hurricane proportions. The 2003 Ford Ranger XLT FX4 turned out to be a huge undertaking. I had to replace just about every body panel and the box, plus replace the engine as well when it blew up. You can read the story here. 

Once it was rebuilt, it was enjoyable. I loved driving that little truck. When my wife and I decided to down size and sold our home, I decided to down size the vehicle list too. I'm the only driver in the family, so the extra insurance and costs weren't consistent with down sizing. So, off it went to another Ford Ranger enthusiast.

But, I missed that Ranger. It was the truck I rebuilt, the truck I loved driving. I started looking around and test drove a few other trucks. I tested a RAM, an F150 and was thoroughly impressed with the car like drive of these full size trucks. So, I sold off the car I had (a Camry) and bought a 2006 Ford F150 XLT. Didn't need much, and I babied it. I added a truck cap, got it all detailed and just really enjoyed the entire truck experience from a different perspective. Up to this point, every truck I had owned were truck-like. This F150 is more like a family vehicle with the added height and heft of a truck. 

I ended up with a few passengers that had difficulty getting into the truck. I thought I was being nice and kind by considering replacing it with a car ... an SUV with AWD that would help out with our heavy snow fall area. And I did just that. I sold the F150 and bought a Taurus X. It's a nice car. But I missed my F150. 

After one year, I decided to look around again. I ended up bying a 2009 Ford F150 FX4. If a truck can be beautiful, this one is. I like the interior, I like driving it, I like how tight it feels and how comfortable the drive is. 

Like all my other trucks, I don't like the fuel economy. It is utilitarian ... that box can haul trash just as well as moving boxes and tools. But they are exposed to all the eyeballs everywhere – and the light fingers that go with it. That's why every truck I have ever owned has ended up with a box cover of some sort. 

My Ford Rangers had truck caps. Some where the high tops where you could also stand inside and some were the sleek looking style with the height even with the top of the truck cab. My first F150 had a tilting textured ABC tonneau cover. I swapped that out for a regular cap. Now I have a tri-fold tonneau cover. 

I'll describe the advantages and disadvantages of all of them. Keep in mind this is my opinion from my own personal experience. My need for a cover for the box was more out of a desire to keep any cargo dry and away from the elements as well as keeping the cargo reasonably secure.

STEP HEIGHT CAP

A step height cap is one that starts out at the same height as the truck cab and has one or more steps to increase its height near the rear of the truck. Some are high enough to stand in, but the ones I had were short of that goal. They were better at taller cargo, but not standing in. The bottom edge of every cap I have ever owned have always completely covered the top part of the box and kept the elements out of the box (as well as bugs/animals). I really only ever had a problem with one cap – it needed two new hydraulic lifts (which were readily available, and fairly inexpensive). Locks were never an issue, they can be replaced inexpensively. The downsize of a truck cap is the weight and the relatively low height. The weight reduces fuel efficiency and make it very difficult to take the cap off and replace it. Unless you design a lifting mechanism for your garage, lifting the cap on and off is a minimum of a two-man job (awkward) or a 3- or 4-man job. You won't need to remove it often, though, unless you want to save on gas or carry cargo like a stove, washer/dryer or refrigerator. While it is the most secure and weather tight, it is also the second least convenient.

TILT TONNEAU COVER

Tilt tonneau covers are typically made of fiberglas. They are available in other materials, the one I had was an ABS textured version branded by Ford (but made by another company). Never had any problems with it at all, the hydraulics worked fine, the lock worked fine. Like the caps above, this type of tonneau cover is completely weather tight, and keeps bugs and animals out. But, talk about useless. Opening this type of tonneau cover forms a triangle shape. The rear of the box is the pivot point and that is the maximum height of cargo at that part of the box. Near the tailgate, you can put in cargo that is up to about 4 feet high, but in a wedge configuration. Removing a tilt tonneau cover is about as user-friendly as the removal I describe above for a cap. It's a minimum two-man job and awkward. I would never buy one again and do not recommend for anyone. It's the least convenient option.

FOLDING/SLIDING TONNEAU COVER

Early tonneau covers were vinyl fit around an aluminum frame sitting on top of the box. They weren't very weather tight and ripped easily. They were secured with snaps along the edge of the aluminum frame designed to hold them down – unless you got the snaps perfectly aligned, they were a PITA to work. Skip ahead a few years and the technology has improved significantly. The basic ones are still vinyl, but most are built on folding frames that are well secured with spring clamps similar to the caps and tilt tonneau covers. They are easy on and off without tools. The vinyl still poses a security risk – anyone wanting access to your cargo just need a dull knife to slice and grab. Most of these newer style tonneau covers are weather tight and attractive. I currently have an inexpensive tri-fold vinyl tonneau cover and like it quite a bit. That being said, I'll probably replace it with a hard tri-fold tonneau cover at some point, just for the added security and protection from heavy snow.

Now for the purpose of this article: fuel economy. Trucks are well designed by the manufacturers to be fairly aerodynamic. They certainly are nowhere near the aerodynamics of a vehicle like the Toyota Prius. By the way, the Toyota Prius has a coeffient of drag (CD) of 0.26 for 2016. Compare that to the 2015 Ford F150 at 0.416. The F150 is a huge beast, but Ford have worked away at it and created a reasonably smooth air flow all around the F150.

I recall years ago when some guys would take the tailgate off their trucks so they could get a few more miles out of a tank of gas. What I find really weird now is that tests show that removing the tail gate actually makes the truck LESS fuel efficient (US tests, by 1 MPG). 

Aerodynamics is not the science of perfectly smooth air flow, it is the science of all parts working together to create the proper drag, pull, and push needed to reduce rolling resistance of the tires. To apply that to the truck with the tail gate removed: think of the car at the race track with the huge air foil on the rear of the race car. That air foil is actually creating more drag with air flipping upward off the foil and creating a downward pushing effect on the rear of the vehicle. A matching air foil is at the front of the race car doing the same thing: a downward pushing effect on the front of the vehicle. Why? That's to work hand-in-hand with the skirts all around the vehicle and create a suction effect pulling the vehicle closer to the pavement (or pushing it down). That reduces rolling resistance of the tires as the speed increases and reduces the amount of gas needed to gain additional speed. The "science" is in finding the right balance of wing design that will not create too much down force and end up creating excess rolling resistance. A heavy tome, but you can read about it here.

Air foils is something I never really got involved with when I raced. I was just a back yard DIY guy with a hobby that I didn't have the money for. Mine was a daily driver that double-dutied as a quarter-mile rocket every now and then. I do remember, though, that any aerodynamics were of little value under 50 mph (80 Khr). 

That is consistent with the tests I have been running on this inexpensive tri-fold vinyl tonneau cover that I purchased. I drove to pick it up and kept my speed at 90 Km (/hr). Up until this point, I had been unable to get below 15 L / 100 Km, including this trip and despite being light on the accelerator. After adding the tonneau cover, the fuel economy was immediately at 12 L / 100 Km driving exactly the same way, the same route, the same time of day, etc. ... the only variable different was the tonneau cover and its extra weight (likely less than 20 lbs.).

This trip was a total of about 107 Km each way (total 214 Km). Not a really definitive test. I had a trip planned for the following weekend that was closer to 800 Km round trip. A bit more definitive. And, here's the results:

My trip started on Highway 404 south bound near Stouffville. I travelled the 404 south bound to 404 west bound to 402 west bound, ending up in Sarnia Ontario. The 404 southbound had heavy traffic at the 401 junction. The 401 west bound had heavy congestion and construction. The construction was throughout the mail Toronto area, in the Milton area, in the Kitchener area, and in the Woodstock area. The 402 eastbound had several legs of construction with detours as well. Heavy traffic, construction, and detours. Despite the legendary rush hour traffic and these other obstacles, I managed throughout the entire trip to keep the fuel efficiency at 11 L / 100 Km. And ended in Sarnia at that average. My target speed was 108 Km/hr.

My original plan was to duplicate the exact same route for the return part of the trip. I was not able to do that. I ended up with about 500 lbs more of cargo than the first part of the trip, and I ended up driving about 20% more mileage, on hilly backroads. The traffic was only heavy in one small area (weekend cottage traffic), but I did end up in a major construction zone where a bridge was out. Big detour and slow stop-and-go traffic. My target speed was 96 Km/hr and I managed to end up with an average of 12 L / 100 Km.

When I consider that the best I could manage was 15 L / 100 Km – with an empty truck, only one passenger, and same light style of acceleration and slow driving – I am thrilled. A gain of 3 L / 100 Km immediately and a stretch at 4 L /100 Km is excellent in my book. 

I do have a theory of why one part of my results showed 11 L / 100 Km ... recall above where I mentioned that aerodynamics are only practical starting at 80 Km / hr ... well, I think I hit the sweet spot of aerodynamic efficiency with my tonneau cover at 108 Km / hr. That's the part of the trip going to Sarnia. I'll have to try that theory out again.

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