Some thoughts on fuel economy

Some thoughts on fuel economy

In this column, I want to discuss fuel economy (FE), in the hopes that I might give you a few ideas to experiment within your operation.

Note that I said “experiment.” My experience has been that no matter what you hear or read, you need to check new ideas out in your operation. You need to learn how to test correctly, and then test every time you get a new idea. Remember both the Technology and Maintenance Council and the Society of Automotive Engineers have developed a series of good, repeatable test procedures you can use in your operation. A poorly run test can give you misleading results.

Let me give you my thoughts. I favor aerodynamic improvements over slower vehicle speeds because I often see big trucks impeding traffic flow in high traffic density situations. These impediments serve to give trucking an even worse reputation, which it doesn’t need.

Aerodynamic improvements can allow you to save fuel even at higher vehicular speeds. I would personally experiment with aero improvements even if products weren’t get commercially available. Build a prototype. I guarantee you that if you can find a way to save 5% or more, you can find someone to build the equipment for you. Look at the trailer tails on trucks hauling BMWs.

The gap between the tractor and trailer intrigues me. I would like to see a device which completely closes that gap at speeds over 45 MPH and retracts to allow maneuverability at lower speeds. Surely our inventive minds can come up with something that works.

I would also like to see side skirts that completely enclosed the trailer wheels and even the tractor rear duals if at all possible. Think of the possible fuel economy benefits of such a device.

Another advantage of such skirting would be vastly improved splash and spray performance. We’ve done a terrible job with splash and spray over the years, and this is another item which gives trucking a bad reputation. It is particularly important with inclement winter weather coming.

Want more insight from John Martin? Click here to see all of his columns.

As far as slower speeds go, speed reduction results in FE improvements in two areas. Slower speeds reduce aerodynamic drag, which improves FE. Slower speeds also reduce engine RPMs, which improves FE due to reduced engine pumping losses.

Visualize the engine as a large hypodermic syringe. The cylinder is the large volume, and the inlet tract represents the filler tube. As you know, if you try to fill the syringe too rapidly (higher speeds), uneven filling and poor mixing results. At slower speeds, the filling is more complete, and the air/fuel mixture has more time to mix in a homogeneous way.

My experience running FE events on both cars and motorcycles over the years suggests that you should use the slowest engine speed possible. A long stroke engine operated at very low speeds is the most efficient FE engine. Look at old Harley-Davidson V-twins and marine diesels as good examples. I never operated the engine in our old Shell Mileage Marathon vehicle over 1,300 RPM. I never idled. And the 376.59 MPG record we set in 1973 has never been broken. I rest my case.

I think a straight through transmission with a low numerical gear ratio is best for FE, due to the lack of friction. You can always downshift if you can’t pull the load.

And what about spiral bevel rear axle gears instead of hypoid? Hypoid gears increase frictional drag considerably over spiral bevel gears. Even the lubrication requirements are more stringent. One of the reasons why front wheel drive passenger cars get better FE than rear-wheel drive cars is that many of them use spiral bevel axle gears. We need to look at this more closely. I know diesel fuel is relatively cheap right now, but you and I both know that this won’t last forever.

You May Also Like

Goodyear, Gatik demonstrate accurate tire-road friction potential estimate

The breakthrough will add more utility to what a tire can deliver by providing critical data that can help enhance vehicle safety.

Goodyear and Gatik have demonstrated, in a proof of concept, that intelligent tires powered by Goodyear SightLine technology can accurately estimate tire-road friction potential and provide real-time information to Gatik's automated driving system.

Goodyear and Gatik deployed road-friction detection capabilities in Canada through continuous measurement of tire sensor-derived information, which is paired with other vehicle data and connected to Goodyear's cloud-based proprietary algorithms to optimize vehicle performance. Friction estimates from Goodyear’s SightLine solution were successfully able to detect low grip conditions, such as snowy or icy conditions, and make this information available to Gatik’s autonomous fleet, enhancing safety and performance for Gatik’s commercial operations in Canada’s challenging winter climate.

So you want to write for Fleet Equipment?

Of course you do. As the premiere online publication for the heavy-duty truck market, charting the latest in trucking equipment, technology, and service trends, Fleet Equipment has a knack for digging up the stories behind the stories (while having a lot of fun along the way). Now you can be a part of it! But

Write for Fleet Equipment
Babcox Media mourns the passing of Tim Fritz, longtime editor and friend

Babcox Media Editor Tim Fritz passed away on Feb. 23 from a heart attack. He was 53 years old. Related Articles – Debating the merits of ethanol – Why isn’t a truck’s appearance part of the PM process? – Change is coming to U.S. energy policies Tim joined Babcox Media in 1990 and spent 31

What’s behind the slow adoption of FA-4 oil?

Introduced three years ago, the American Petroleum Institute (API)’s CK-4 and FA-4 oil categories were billed as the next generation of oil, improving on the engine protection and fuel economy benefits offered by previous engine oil categories.

How will today’s ‘customer focus’ translate to tomorrow’s electric trucks?

Over the past three years, OEMs have invested heavily in driver-focused equipment benefits—from cozy creature comforts to uptime- and productivity-boosting technology. Today, significant R&D investment is going into the development of electric trucks—probing the possibilities of untested powertrains in hopes of producing a product that meets application needs.


Other Posts

Auto Value, Bumper to Bumper and All-Pro Truck Parts highlight Alliance Commercial Vehicle and Heavy-duty Program at HDAW

The Alliance looks toward continued growth in the medium- and heavy-duty aftermarket.

Photo Gallery: Heavy Duty Aftermarket Week 2023

A pictorial walk-around of the show floor.

Dayco expands heavy-duty diesel engine belt kit line

Six new SKUs join the 40-plus that Dayco has recently added.

Cummins-Meritor talks acquisition impact, aftermarket support

Here’s how the brands come together and do business in the market.