After what you are paying yourself, fuel cost is likely your biggest monthly expense. And, while there are always limits, it's surprising what can be done to shave that cost down. Here are 6 things you can do without much capital investment:
1. Drive for Fuel Economy
You may have read our article, Fuel Economy: Part 1 - The Driver Makes all the Difference, which covers fuel economy driving extensively. Below is a brief summary:
Lower your RPM
The most efficient diesels are those on big ships that may turn at less than 100 RPM at cruise, and there is a lesson there. Diesels become more efficient as you lower your RPM. Of course, you need to get the job done, and you also need to avoid excessive vibration and pressure stress on the engine by avoiding continuous operation under heavy load below the engine's torque peak. But, in general, using the fastest gear you can for every situation, once the truck is moving and you release the clutch, is the best practice. This means progressive shifting: shifting up very early when going through the lower gears with light throttle, and always cruising and even climbing hills in the highest gear that will get the job done. Running a 13- or 18-speed is advantageous in that, when climbing hills, you can split down rather than dropping a full gear, which often allows you to make the climb at a slightly lower RPM than a full shift down would provide.
Lower RPM reduces friction, and also raises the fuel/air ratio, which heats up both the air in the cylinder and the exhaust. That, in turn, spins the turbo faster, helps the engine breathe better (because there is more time during each intake and exhaust stroke for flow along with more boost pressure), and heats up the air in the cylinder to a higher temperature, providing much more pressure on the power stroke. Slow revs also give more time for the fuel to burn. You can shift at 1,200 RPM or less in the lower gears, and should always end up below the torque peak after the shift at lower loads, and about at the torque peak under maximum throttle.
Minimize braking
Also, minimize braking whenever possible‚ even the use of the engine brake. Braking of either kind is the largest single waste of fuel you‚Äôll encounter. Doing this means anticipating traffic that is slowing and taking your foot off the throttle early so you can use the inertia of the vehicle to move you to the next traffic light, if it's red, or to get you up to where traffic is slowed for any other reason without burning more fuel. Also, slow when cresting a hill so you won't need to brake to keep from building up too much speed before you reach the bottom. You'll save all the extra fuel that would have been needed to maintain your cruising speed while climbing that hill. If you drive a route regularly, you can learn how much speed you should have at the top of each hill.
65 MPH provides a good compromise between productivity and fuel savings on good highways with a modern aerodynamic truck. But, in general, lower cruise speeds help a great deal to save fuel because the wind resistance you encounter goes up quite rapidly at higher speeds. Tire friction also increases quite a bit with speed. When encountering a strong headwind, cutting 5-10 mph off your speed will save a significant amount of fuel.
When on busy inner-city expressways, cruising at 55 mph or even less (just a bit slower than much of the traffic) will save fuel by reducing the need for braking. As said, braking is the single biggest waste of fuel.
2. Avoid Idling and install an alternative power unit
Outside of your driving technique, there are many changes you can make to save on fuel consumption. Never idle overnight, but instead provide some kind of alternate method of heating and cooling your cab and APU with a small diesel, or even some sort of battery-powered AC unit or a system that stores cold from the sleeper AC while you drive, then uses the cold storage system to cool the cab while you rest.
Diesel fuel fired heaters do a great job of keeping the cab warm at very low cost, and are practical as long as you have enough reserve battery power to handle long discharge times at low loads to provide electrical power for the heater. A Deep Cycle battery that can keep your accessories working overnight without a shortened life or a large enough group of batteries that can both handle overnight loads and still crank the engine is ideal. Specialized batteries that have a lot of Reserve Capacity are the ones that will help you there. It's possible to have 3 batteries with high ratings of CCA or Cold Cranking Amps for starting, as well as a couple with high Reserve Capacity to handle overnight use of electricity. There are also batteries that can offer a good combination of both characteristics.
You can purchase inverters that will power your AC accessories like a fridge in the sleeper or power your computer. These will cut off power when your batteries reach the point where they won't start the diesel. Another advantage of them is that you can then use 120-volt AC refrigerators or other appliances, which are much more efficient than 12-volt DC ones. One excellent strategy for the cold is a diesel-fired heater that heats the engine coolant. This will allow you to keep the cab and sleeper warm using the standard heater that uses warm engine coolant and the blowers in the dash and sleeper while also keeping the engine warm enough to start easily.
And, by the way, idling the diesel is very hard on the engine itself and the oil. It's been shown that, if you do oil analysis, you'll significantly delay oil changes if you don’t idle. The amount of engine wear and deterioration of the oil is out of proportion to the actual amount of fuel burned during idling, meaning much higher than what occurs from using that much fuel while driving down the road. While combustion systems have improved greatly, so this effect is less acute than in the past, it’s still much smarter to shut the engine off. The piston rings don't even seal properly at idle because of the low cylinder pressure. This allows blowby gases to deposit much unburned or incompletely burned fuel and acids into the oil. Better combustion occurs under normal operating conditions, and that also means much less engine and oil deterioration.
Also, starting a warm engine by pre-heating it with a diesel-fired heater or even plugging it in and using an electric block heater is ideal for helping to keep the DPF clean. This also reduces the wear encountered during cold starts because of the delay in oil getting into parts like the piston rings.
3. Replace your Tires and align your axles
Replacing the tires you may have with low rolling resistance tires is also a good idea. And just keeping tires fully inflated is critical in reducing tire friction, which becomes heat and shortens the life of the tire when it's under-inflated anyway. Automatic tire inflation systems that keep tires pressurized properly at all times using the air from the truck's air system do a more consistent job of keeping tires inflated than even the most attentive truck owner.
You can even get systems that will adjust the pressure up and down with your load, as fully inflated tires don't have a good contact patch when you are running empty.
Getting both your tractor and your trailer's axles (if you own one) fully aligned at least once a year will also save a lot of fuel. Any scrubbing of tires due to poor alignment costs both at the fuel pump and at the tire shop, of course.
4. Adjust your Wheel Bearings
Proper adjustment of wheel bearings is another helpful area. Make sure you visit capable shops when bearings are greased or replaced, or do the job precisely as recommended by the factory if you do the work yourself. The bearing must be snug enough to keep it running true, yet without excessive load on the bearing parts. A procedure involving a number of steps and using a torque wrench or dial indicator is the only way to do this job properly. There are also premium factory-adjusted bearing systems that are adjusted properly with spacers so all you need to do is torque everything in place after installation.
5. Choose a lower viscosity Lubricant
Lubricants play a tremendous role in reducing friction in the engine, transmission, and axles. So choosing lower viscosity lubricants is another area that can be fruitful in saving fuel.
Types of engine oil
The latest generation of diesel engine oil, CK-4, is specifically formulated to provide the viscosity and wear protection needed to ensure long life of your engine while also minimizing friction.
Its cousin is FA-4, sold in familiar viscosity ranges, but specifically formulated to reduce friction in the ring belt area at the top of the piston. Because the piston rings spring outward and develop even more pressure on the walls of the cylinder liner when the engine fires, they are a significant source of friction. That's why FA-4 is tested in that part of the engine.
FA-4 is slightly less viscous or thick than CK-4, although still within the range of the viscosity listed on the label. Make sure not to use FA-4 except on the latest engines it is approved for. As of 2017, many engines were required to be able to function with its slightly thinner oil film because of the way parts are finished. Significantly smoother surfaces allow a thinner film of oil that still keeps the tiny metal protrusions that exist on all parts from actually touching. Earlier engines with surfaces that are just slightly rougher won't tolerate this oil grade well, and will see unnecessary wear if it is used.
Although fleets have been cautious in adopting FA-4, newer engines for which it is approved can operate more efficiently‚ and still quite safely--when it's in the crankcase.
Even if running an earlier engine or wishing to avoid any risk, using CK-4 rather than an earlier oil designation in your engine (like CJ-4) to save money on lube means unnecessary friction and poorer fuel economy.
Adjust based on conditions
An additional approach is to choose a lower viscosity oil that is still approved for your particular engine. Many engine manufacturers in recent years are fine with 10W-30 oil, especially when not hauling heavy loads on steep grades or in extremely hot weather. Check your owner's manual to see if such a lower viscosity oil is approved in the conditions you are operating in. While a conservative approach‚ using the traditional 15W-40 oil if hauling heavy loads in the mountains in summer--may be best, if your truck or engine owner's manual approves the use of 10W-30 in the load and temperature conditions you are experiencing, you will definitely save fuel by using such an engine oil. Such lubes use a slightly thinner base oil that is easier for the oil pump to distribute while also making parts slide over one-another more easily. Exotic additives that have little effect on the viscosity or thickness of the oil but still ensure protection by keeping moving parts from actually contacting one another are the secret sauce of lower-viscosity oils. Many full synthetic or semi-synthetic oils may offer a wider viscosity range, like for example 5W-30, that will help reduce friction especially during cold starting and the first couple miles of operation in cold climates. Just make sure the full viscosity rating (check both numbers) is approved by checking your engine or truck owner's manual.
Synthetic lubricants
Synthetic lubes for your transmission and drive axles are also a potent way to save fuel. Synthetic transmission lube costs much more than mineral lube, but it will reduce friction considerably and last much longer, more than paying for itself. The savings include reduced downtime‚ you could be out on the road making money instead of changing your transmission fluid while making several changes.
The best of these lubes also help make your transmission live longer as they avoid deposits. They retain their viscosity rather than thinning out from heat and shear, while also avoiding oxidation, which produces destructive by-products. They are also said to have a more favorable viscosity index. This means they greatly affect the ease of making those first few shifts on cold mornings because synthetics offer adequate viscosity at high temperatures while thickening less as they get colder. That greater fluidity also more quickly covers parts with lube to protect them after you start out in the cold. Synthetics are even said to be slightly slipperier at the same viscosity.
Ensuring the proper viscosity for your truck
Just make sure to use the proper viscosity for your particular transmission. Approved synthetics are often required for use during warranty periods anyway. But if you are running older equipment that is off warranty, use of a good quality synthetic that is specifically approved by the component maker is still ideal and will save fuel. One manufacturer of manual transmissions approves 50-weight engine oil for use, but also approves a specially-formulated synthetic. The change interval for the engine oil, which is a mineral lubricant, is 60,000 miles or one year, while for a synthetic of special spec’, the interval is 500,000 miles or 5 years.
Drive axle lubricants generally come in two viscosities at this time, 75W-90 and 80W-140. There is no clear standard on which lube is ideal for your work. But, over-the-road trucks not hauling overweight loads or running much of the time on steep grades will likely be fine with 75W-90. The heavier 80W-140 is likely ideal for those hauling in vocational service, on-off road, with heavier loads, and especially when running in very hot weather. Highway cruising is much easier on these lubes than service where the truck stops and then is started up using the lower gears.
But even when using synthetic axle lubes of 75W-90 viscosity, special low-friction, long-life fluids are often approved for much longer change intervals -- for example from 180,000 miles/3 years to 500,000 5 years, and you can save money on lubricants and downtime by using them.
6. Install an Aerodynamic Device
If you spend most of your time on the highway, you can be certain that most of your fuel is used to push air around the rig. Any device you can add to either the tractor or the trailer will help the fuel bill, while also lengthening the life of your entire powertrain and even the engine oil. It will also lengthen the life of drive tires!
These devices range from tractor roof-mounted air shields (Nose Cone is one manufacturer), inter-axle aero devices like those made by FlowBelow, to aero wheel covers that allow air to smoothly pass over the wheel rather than being trapped by the indentation where outer duals are mounted. Various types of side skirts may also be available, and should be specified on new trucks or their presence should influence your choice of a used one.
Trailer aero devices include the most popular type: the side skirts that mount underneath on both sides. One manufacturer is AeroFlex, though there are many competitors. While these can increase maintenance costs, if you are careful about running over curbs and choose devices that are either mounted flexibly or have a flexible band at the bottom, repairing them should not become an issue. They save a lot of fuel because without them air flows rapidly under the trailer, which normally has a ribbed structure, and that generates a lot of air resistance. With side skirts, air flows smoothly around the trailer and a mass of air that mostly moves right along with the trailer is trapped underneath. There are also rear trailer devices of various types with one popular manufacturer being named Trailer Tail. And there are some that mount at the rear of the trailer on the sides, and some that move out on either side behind the trailer doors when deployed.
These, of course, will not work well unless you are vigilant about deploying them as soon as you close and lock the trailer doors. But, they effectively avoid turbulence generated by the trailer's rear that ends up holding you back. They actually smoothly turn air around and cause it to push gently against the rear of the trailer, rather than generating swirling air that merely holds you back.
While there is much you can do to save on fuel consumption within your existing equipment, the list goes on when considering purchasing newer equipment. Stay tuned for our next post, Fuel Economy: Part 3 - Purchasing New Equipment to learn more.
Other relevant articles:
Fuel Economy: Part 1 - The Driver Makes All the Difference