Introduction
And the price of diesel fuel keeps rising, with every gallon counting when you’re trying to watch your budget. If you’re a diesel truck driver, for business or farm work, or if you’re a commuter who drives a compact (like a VW Jetta TDI), the way you drive will have big impact on how much fuel you burn.
The good news? You don’t require expensive upgrades or fancy gadgets to conserve fuel. Small adjustments to how you drive can improve your fuel economy by 20% to 30%. That is actual money back in your pocket each month.
Diesel engines already provide better fuel economy than gasoline engines, but very few drivers ever realize it. This guide offers 11 things you can do to keep any diesel vehicle — from passenger cars and SUVs to heavy-duty pickups and big rigs — in good shape. All of these tactics are proven, time-tested and can be put in place starting today.
Let’s get into those gas-saving habits that will change the way you drive and the amount you spend to fill up at the pump.
Why Diesel Vehicles Drive Differently Than Petrol Ones
Diesel engines operate differently from gas engines. They’re compression ignition, not sparkplug equipped, so they respond differently to some driving approaches.
This is because diesel engines have a tendency to produce more torque down the RPM scale. This makes them quite efficient if you use it well. But drive a diesel as if you’re behind the wheel of a petrol engine, and you end up inefficiently burning fuel.
But when you know those differences, you can make smarter decisions behind the wheel. The following tips exploit the special nature of diesel engines.
1. Learn the Art of Accelerating Slowly
Heavy foot is the quickest route to an empty diesel tank. When you stomp that pedal, your engine consumes a lot more fuel to produce that instant surge of power.
For one thing, diesels produce peak torque down low, so they don’t need huge bursts of acceleration to get up to speed. Slow, easy roll-on allows the engine to work with its natural power delivery.
How to do it:
- Apply the gas slowly and consistently
- Get you to highway speeds from a stop in 15-20 seconds
- Keep an eye on your RPM gauge and don’t go over 2,500 when you accelerate
- Picture there’s a raw egg beneath your gas pedal
Just this one change alone can increase mileage by 10% to 15% while you are driving in the city.
2. Maintain Consistent Speed on Highways
Speed fluctuations kill fuel efficiency. Each time you accelerate or decelerate, your engine labors and burns more diesel.
Cruise control is your best friend on long drives down the highway. It doesn’t vary the speed at which it maintains itself, as you might if you were controlling the pedal by hand.
The diesel vehicles that can be the most cost-effective:
| Speed Range | Mileage Impact |
|---|---|
| 45-55 mph | Best mileage |
| 55-65 mph | Good mileage |
| 65-75 mph | Okay mileage |
| 75+ mph | Worst mileage |
Wind resistance increases dramatically over 65 mph. You’re using roughly 20% more fuel going 75 mph vs. 55.
Do your best to stick to 60-65 mph, and at those speeds, let the cruise control do its thing. Your fuel gauge will be grateful.
3. Anticipate Traffic Flow Ahead
Scanning far down the road allows you to minimize unnecessary braking and accelerating. That is called “reading the road,” by professional truck drivers, and it’s one of the most powerful techniques for saving fuel.
Lift off the gas long before you come to brake lights ahead or a red traffic signal in the distance. Wind down a bit rather than rushing straight up to the obstacle and slamming on the brakes.
Benefits of anticipation:
- Fewer complete stops
- Less wear on brakes
- Smoother ride for passengers
- 5% to 10% better fuel economy
This is particularly effective in diesel engines, which are cut from a different cloth because they coast better on account of their higher compression ratio.
4. Use the Highest Gear Possible
The modern diesel engines are capable of creating considerable torque at lower RPM. This, in turn, allows you to hit higher gears sooner than you’d expect.
If you drive in too low a gear, your poor engine has to work harder than it needs to. Taller gears decrease engine RPM and fuel consumption for a given vehicle speed.
For manual transmissions:
- You can change gears at 2,000 RPM
- Do not be afraid to use 5th or 6th gear at slower speeds
- Skip gears if it’s safe (going from 2nd to 4th)
For automatic transmissions:
- Use “Eco” mode, if applicable to your car
- Stay out of “Sport” for everyday driving
- Many cars have a manual mode – and you should use it to prevent unwanted gear changes
Maintaining RPMs in the 1,500-2,500 range gives you the most power and efficiency.
5. Reduce Unnecessary Weight and Drag
Each additional 100 pounds in a vehicle decreases fuel economy up to 1% or 2%. That may not seem like a lot, but it adds up fast.
Common sources of excess weight:
- Tools/gear you don’t use every day
- Sports gear left in the trunk
- Extra spare parts or materials
- Fully fueled tanks when you don’t need them (long trips only)
Aerodynamic drag matters far more than weight at highway speeds. Roof racks, bike carriers and cargo boxes all create wind resistance, making your engine work harder.
Take down rooftop accessories when not using them. One roof rack that’s lacking a ski, bike or cargo box can lower fuel economy by 5 percent on the highway. It can go down 15 to 25% if you have a loaded cargo box.
Even little things add up — for example, rolling a window down at highway speeds causes a lot more wind resistance than you might think.
6. Maintain Proper Tire Pressure
Driving on under-inflated tires creates rolling resistance and can cause your engine to burn more fuel. One of the most common yet often-forgotten ways to save diesel.
At least monthly, check your tire pressure. Temperature has quite an effect on pressure — tires drop about 1 PSI for every 10-degree temperature decrease.
Proper tire maintenance:
| Tire Condition | Fuel Economy Impact |
|---|---|
| Proper pressure | Baseline |
| 5 PSI low | 2% loss |
| 10 PSI low | 4-5% loss |
| 15 PSI low | 8-10% loss |
Look up the recommended pressure for your vehicle on the sticker inside your driver’s door, or in the owner’s manual. Do not use the maximum pressure stamped on the tire sidewall because that is not your vehicle’s recommended pressure.
Invest in a good quality tire pressure gauge. The little you have spent would have earned itself by way of fuel savings in just 30 days.
7. Minimize Idling Time
Diesel engines consume fuel when they’re running, even if they’re not moving. Newer diesel engines don’t require the same warm up time that older ones used to.
Idling fuel consumption:
- Light-duty diesel: 0.3 to 0.5 gallons per hour
- Heavy-duty diesel: 0.8 – 1.2 gallons per hour
If you will be idling more than 60 seconds, turn off your engine. It takes less fuel to restart than to idle for a minute or more.
Common idling situations to avoid:
- Waiting in parking lots
- Drive-through lines
- Warming the car on a chilly morning
- Telephone use while parked
New diesel engines heat up more quickly driving slowly than while idling. Begin driving moderately within the next 30 seconds of vehicle operation.
8. Plan Your Routes Strategically
GPS apps such as Google Maps and Waze do more than just show you the quickest path from Point A to Point B; they guide you away from fuel-wasting situations.
In heavy traffic with a lot of stop-and-go your miles per gallon can drop by 40% versus getting into true flow traffic. A slightly longer route with fewer traffic jams might even be, counterintuitively, the better way to go for your gas.
Route planning considerations:
- Avoid rush hour when possible
- Bundle errands into a single trip
- Opt for highways, not streets, on longer treks
- Stay off roads with a lot of stop signs and traffic lights
Cold engines are less efficient than warm ones. Try to combine errands and run them as a batch when possible instead of taking many short trips during the day. Your car runs best after it’s reached normal operating temperature. For more strategies on optimizing your driving habits, visit Fuel Saving Driving for comprehensive guides and tips.
9. Service Your Engine Regularly
A well kept diesel engine is an efficient engine. All told, routine upkeep can stop minor problems from turning into fuel-wasting nuisances.
Critical maintenance items:
| Service Item | Change Intervals | Fuel Economy Effect |
|---|---|---|
| Oil changes | 5,000-7,500 miles | 1-2% |
| Air filter | 15,000-30,000 miles | 5-10% |
| Fuel filter | 10,000-15,000 miles | 3-5% |
| Fuel injectors | 50,000-100,000 miles | 10-15% |
A dirty air filter blocks the inflow of fresh air, causing your engine to work overtime. An obstructed fuel filter restrains optimal flow of gasoline in the vehicle’s system. Used motor oil generates more friction among working parts.
Follow your manufacturer’s maintenance schedule. Use the correct grade of diesel engine oil—using improper viscosity can degrade fuel economy by 2% to 3%. According to the U.S. Department of Energy, regular maintenance can significantly improve your vehicle’s fuel efficiency.
10. Use Air Conditioning Wisely
Air conditioning is always a fuel vampire in any vehicle, but its effect depends on how you use it.
Your air conditioning system is powered by your engine so it steals energy that could be used to move your vehicle along. At low speeds, that effect is significant — up to 20% loss of fuel economy.
Smart AC strategies:
- Park in shade wherever possible to keep cabin cooler
- Use ventilation instead of AC at speeds less than 40 mph
- Roll down windows for city driving
- On the highway, use AC (open windows create drag)
- Set temperature at 72-74°F instead of coldest
- Use recirculation mode once the cabin has cooled off
When it’s oppressively hot, you will want AC for your safety and comfort. Just use it mindfully, instead of turning it up to the max on autopilot.
11. Monitor Your Fuel Economy Actively
You can’t manage what you don’t track. When you keep track of your fuel economy, it’s easy to see which driving habits put more miles in the tank and which ones are just wasting fuel.
Diesel cars generally come equipped with a gauge that measures the fuel economy since last fill up. Use them to instantly understand how your driving impacts consumption.
Ways to track fuel economy:
- Use your vehicle’s trip computer
- Manually derive MPG upon each fill up
- Use a smartphone app to keep track: Fuelly, Drivvo
- Keep a car logbook in your vehicle
Keep an eye on your instantaneous MPG display in real time while driving. You’ll soon discover how acceleration, speed and traffic conditions affect your numbers. This real-time feedback enables you to correct your habits on the fly.
Establish monthly fuel-efficiency targets and monitor your progress. Those small savings can add up to big money over time.
But How Much Money Can You Really Save?
Now let’s see these tips in action by the numbers.
Suppose you drive a diesel truck that typically gets 20 MPG. You drive 15,000 miles annually, and diesel fuel is selling for $4.00 a gallon.
Current annual fuel cost: $3,000
By following these 11 tips, you can realistically boost your fuel economy by as much as 20% to 25%, and increase your MPG up to around an impressive 24-25.
New annual fuel cost: $2,400 to $2,500
Annual savings: $500 to $600
That is genuine money that you can use for other things. In 5 years or so, you’d bank $2,500 to $3,000 by nothing more than changing the way you drive.
5 Diesel Fuel-Wasting Mistakes to Avoid
These are some of the expensive mistakes that drivers, even ones who imagine they’re being efficient, frequently make:
Running warm up too long: It doesn’t take 10 minutes for your diesel to warm up. Begin to drive gently after 30-60 seconds.
Filling up with weak fuel: If you use “dirty” diesel that has a high concentration of contamination, efficiency will drop and your fuel system can suffer. Stick to reputable stations.
Ignoring dashboard warnings: Your check engine light typically warns of problems that cause a car to burn more fuel inefficiently. Address issues quickly.
Overloading your car: Keeping more stuff on your car than it’s designed to carry causes the engine to use much more power.
Aggressive driving: Rapid acceleration and hard braking can lower your gas mileage by 15 percent to 30 percent at highway speeds and by 10 percent to 40 percent in stop-and-go traffic.
Steering clear of these mistakes ensures the health of your fuel economy — and the health of your car.
Frequently Asked Questions
Q: Are premium diesels good for fuel economy?
A: A premium diesel should clean your fuel system better, but we typically don’t see enough of a fuel economy improvement that it justifies the extra cost. Fill up from reliable diesel stations with standard diesel.
Q: Can fuel additives help me get better diesel mileage?
A: In most cases the additives in diesel are sufficient. Other products offer little improvements in fuel mileage. Focus on driving habits instead.
Q: How does cold weather impact diesel fuel mileage?
A: Cold air can cut gas mileage on a tank of fuel by 10% to 20%. Diesel engines are also slower to warm up, and thick fuel is less efficient. Use your parking garage, and if you live up north in very cold states, use block heaters.
Q: Can better engine tuning or chips help with fuel economy?
A: Some programming can be made for efficiency, but most performance chips are about power over economy. If you’re going to consider this, make sure the tuning is for fuel economy and find a reputable installer.
Q: Should I wait until my tank is nearly empty before filling up?
A: Fill up whenever convenient. The old wives’ tale about fuel evaporation doesn’t apply to modern sealed fuel systems. But maintaining at least a quarter tank stops sediment from getting into your fuel system.
Q: Do the diesel fuel economy tips apply to biodiesel as well?
A: Yes, these driving tips are applicable across all fuel types. Biodiesel generally has slightly less energy per gallon, so you may have a somewhat lower MPG (even driving perfectly).
Conclusion
Fuel savings in diesel vehicles doesn’t have to be expensive or complex. With these 11 tips, the emphasis is on driving your car smarter, keeping it well serviced and opting for some small changes that can help towards a big effect.
Begin with the low-hanging fruit—gentle acceleration, constant cruising speed and reduced idling. Once these become second nature, introduce more advanced strategies such as route planning and real-time fuel economy monitoring.
Every gallon you save means more money in your pocket and less of an impact on the environment. Diesel engines are efficient enough as it is, but they work best when monitored with smart driving practices.
Choose two or three ideas from this list and focus on them this week. Monitor your fuel economy and see the changes. When you have those habits down, add more of the techniques to your routine.
Your diesel truck has tons of untapped potential for fuel efficiency. These 11 tips show you how to unlock that potential, so you keep more of your hard-earned money where it belongs — with you, not at the fuel pump.
