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Key Takeaways
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Engine braking uses the engine’s internal resistance to slow the truck instead of relying on the service brakes.
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Jake Brakes® provide stronger, more efficient deceleration when used in the correct gear, rpm range and road conditions.
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Proper engine braking improves safety, lowers fuel use during deceleration and extends the life of your service brakes.
If you drive a heavy-duty diesel truck, you already know there’s a big difference between slowing down with your service brakes and slowing down by letting the engine do the work.
That second method is called engine braking. And when it’s used correctly, it saves fuel, reduces wear on your brake system and gives you far more control on the road.
Below, we’ve covered what engine braking is, how it works, how to engine brake properly and how often to service your engine brakes to keep them performing at their best.
What Is Engine Braking?
Engine braking is a method of slowing down your truck by using the engine’s internal resistance instead of relying solely on the service brakes. In gasoline cars, “engine braking” just means lifting off the accelerator and letting the engine’s natural vacuum slow the vehicle.
But in diesel trucks, engine braking is more advanced.
A compression release engine brake (commonly known as a Jake Brake®) opens the exhaust valves near the top of the compression stroke, releasing the compressed air instead of using it to push the piston back down. This turns the engine into a massive air pump that absorbs energy and slows the truck.
The result:
- Greater control, especially on long grades
- Reduced brake heat
- Less wear on friction components
- Zero fuel use during deceleration
When drivers say they’re “using the Jake,” they’re talking about this specific type of engine braking system.
Fun Fact: Compression release engine brakes get the name Jake Brake from the Jacobs Engine Brake®, a type of engine brake introduced by Jacobs Vehicle Systems in 1961.
How Does a Jake Brake Work?
To understand how a Jake Brake works, it helps to compare two engine cycles:
Normal Operation:
- Air is drawn in.
- Air is compressed.
- Fuel is injected and combusted.
- Power is delivered to the crankshaft.
With the Jake Brake Activated:
- Air is drawn in.
- Air is compressed.
- Before the piston reaches top dead center, the exhaust valve opens.
- The compressed air is released, and the energy that would normally push the piston down is lost.
This forced release of pressure absorbs massive amounts of power, slowing the truck quickly. Modern diesel trucks automatically shut off fuel injection during engine braking, so you’re slowing down at zero fuel cost.
How to Engine Brake for Maximum Benefit
Engine braking delivers the greatest results when it’s used correctly and in the right conditions. Here’s how to get the most out of it.
1. Engage the Engine Brake Properly
Most modern trucks are equipped with a multistage Jake Brake using Low/Medium/High settings (or Stage 1/2/3). Each stage increases braking force by activating more engine brake housings.
To use it correctly:
- Turn on the engine brake switch.
- Lift completely off the accelerator pedal: Engine braking won’t activate unless your foot is off the accelerator.
- Keep the rpm within the optimal range: Many engines operate best between 1,500 and 2,200 rpm, but refer to your specific engine manual for details. A higher rpm means stronger engine braking.
- Select the appropriate stage: Use low for gentle deceleration or slick road surfaces. Use medium for moderate slowing or rolling terrain. Use high for steep grades, heavy loads or controlled descents.
If your truck has an automatic transmission, the system may downshift to keep the engine rpm in the engine brake zone. Manual-transmission drivers need to manage this themselves.
2. Use the Correct Gear
An engine brake is not tied to road speed. It’s tied to rpm. If the rpm drops too low, the Jake Brake simply can’t produce enough braking force.
To maintain strong, consistent deceleration, make sure you:
- Downshift before the rpm falls out of range.
- Stay in a gear that keeps the rpm high enough for strong braking but below the engine redline.
- Avoid over-revving. Never rely on the Jake Brake to hold unguided high rpm. It should always stay within the manufacturer's limits.
As mentioned above, trucks with automated manual transmissions may downshift automatically to support engine braking, but drivers should still monitor the rpm during descents.
3. Use Engine Braking Early, Not Late
Engine braking works best when drivers anticipate slowdowns and use the Jake Brake as part of a planned, controlled speed reduction — not as a last-minute reaction.
Use it early when:
- Approaching red lights or congestion
- Entering curves, freeway ramps or roundabouts
- Descending a long downhill grade
- Moving through dense or stop-and-go traffic
- Maintaining a safe buffer on rolling terrain
Activating the Jake Brake early prevents brake heat buildup and reduces pressure on service brakes, which is good for extending the life of your truck. It also gives the driver a smoother, more controlled deceleration.
4. Avoid Using It on Icy or Slippery Surfaces
Engine braking applies significant torque to the drivetrain. On low-traction surfaces, this can cause the drive wheels to slip or lock, especially on empty or lightly loaded trailers.
Use caution when:
- Roads are snow-covered, icy or frozen
- Driving over black ice
- Passing over metal bridge joints or painted surfaces in winter
- Descending a grade with patchy ice
Many fleets instruct drivers to either use only the lowest Jake Brake setting on slick roads or disable it entirely in heavy ice conditions.
5. Don’t “Ride” the Brakes on Grades
On long downhill grades, relying solely on service brakes generates heat, causes brake fade and results in a dangerous loss of stopping power. Engine braking should be the primary control method for holding speed.
To descend safely:
- Use the Jake Brake as the main braking system.
- Apply service brakes briefly and firmly when needed, then release them.
- Let the engine brake carry the load rather than dragging the foot brake.
- Choose the right stage before descending a hill.
Proper use of engine braking keeps brake temperatures low and prevents fade, which is critical for both safety and brake longevity. Add regular servicing to your maintenance plan to ensure both your service brakes and Jake Brake are in good shape.
When Will You Feel the Effects of Engine Braking?
You’ll feel the effects of engine braking almost immediately once you turn on the Jake Brake, remove your foot from the accelerator and the rpm rises into the braking range.
Higher stages create a stronger, more noticeable braking effect. On long downhill grades, the difference is dramatic. Engine braking can hold your speed steady with minimal service brake input.
Ensure Your Engine Brake Is in Good Shape
Engine braking is an effective way to protect your service brakes, improve fuel efficiency, and stay in control on steep grades or heavy routes.
When your Jake Brake is tuned and kept in good shape, you get smoother deceleration, cooler brakes and a safer, more predictable driving experience. That’s why regular inspections (every 300,000–500,000 miles or during an engine overhaul) are essential.
If you want the confidence that your engine brake is working exactly as it should, Rush Truck Centers can help. With more than 140 locations nationwide and factory-trained technicians who understand every component of your engine brake, we offer precise inspections, expert adjustments, and clear parts and labor pricing.
Contact your nearest Rush Truck Centers location today to request a service appointment.
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