This month diesel prices hovered near record highs, with national averages recently well above $5 per gallon, with California nearign $7/gal in early June. Those prices are mercifully coming down, but it’s another reminder that every drop of fuel saved directly impacts a fleet’s bottom line. For heavy-duty Class 8 truck service shops, this creates a prime opportunity to deliver high-value preventive maintenance that boosts MPG, reduces operating costs, and builds customer loyalty. Proper service can significantly improve fuel economy through targeted interventions.

Here are my top five service tips your shop can implement to help trucks run as efficiently as possible.

1. Prioritize Tire Maintenance and Optimization:

   Tires are one of the biggest contributors to rolling resistance in Class 8 trucks. Underinflated tires can cut fuel economy significantly—every 10 PSI drop below recommended levels can reduce MPG by about 1%. During service, always check cold tire pressure against the manufacturer’s specs (typically 100 to 120 PSI for steer and drive tires) and inspect for wear, damage, or punctures. Perform wheel alignments and rotations regularly to prevent uneven wear and drag. Install low-rolling-resistance tires when appropriate, as they require less energy to keep the truck moving. A quick pre-trip tire audit can yield immediate savings and extend tire life, making this a high-ROI service for shops to emphasize

2. Perform Thorough Engine and Filter Maintenance

   A clean, well-lubricated engine operates with minimal internal friction and optimal combustion. Clogged air filters restrict airflow, forcing the engine to work harder and burn more fuel—replacing them can noticeably improve efficiency. Similarly, fresh fuel filters prevent contaminants from affecting injector performance, while timely oil changes with the correct low-viscosity, high-quality diesel engine oil reduce parasitic losses. Shops should follow OEM change intervals but adjust for severe-duty cycles common in trucking. During service, check for exhaust restrictions, such as issues with the diesel particulate filter (DPF), which can increase backpressure and fuel consumption. A comprehensive engine health check, including diagnostic scans for fault codes, ensures everything runs in its most efficient sweet spot.

3. Inspect and Address Brake Drag and Rolling Resistance

   Seized or dragging brakes are silent fuel thieves, creating constant resistance that wastes diesel without alerting drivers immediately. During routine service, technicians should inspect brake components for proper adjustment, lubrication, and free movement. Test for drag by checking wheel-end temperatures or using a rolling test. This ties into overall chassis maintenance—greasing fittings, checking wheel bearings, and ensuring suspension components aren’t binding. Addressing these issues not only saves fuel but prevents premature wear and safety concerns. Shops can bundle this with tire services for efficient bay time.

4. Optimize Fuel System and Injection Performance

   Modern diesel engines rely on precise fuel delivery for efficiency. Service shops should clean or replace fuel injectors if spray patterns are off, check for water contamination in the fuel system, and ensure high-pressure lines are leak-free. Upgrading to high-efficiency fuel filters or recommending quality diesel additives (where approved) can help maintain combustion efficiency. Monitor fuel pressure and timing via diagnostics—small deviations can lead to incomplete burns and higher fuel consumption. In high-mileage fleets, this service prevents the gradual efficiency drop that compounds with today’s expensive fuel.

5. Evaluate and Enhance Aerodynamics and Ancillary Systems

   While core mechanical work is key, don’t overlook external factors. Inspect for damaged fairings, cab extenders, or trailer skirts that increase drag. Recommend aerodynamic add-ons like gap fairings or wheel covers if missing to your fleet customers. Minimize auxiliary loads by checking A/C systems, alternators, and fans — excessive drag here pulls power from the engine. Ensure the cooling system is efficient to prevent the fan from engaging more than necessary. Shops can offer comprehensive efficiency audits that include these checks, positioning themselves as partners in cost control.

Implementing these tips requires a proactive, checklist-driven approach in your service bays. Train technicians on fuel-efficiency diagnostics, use data from telematics where available, and follow up with customers after service to verify MPG improvements and to demonstrate value.

In an era of diesel price volatility, shops that excel at these services will stand out—helping fleets cut costs by hundreds or thousands per truck annually while keeping vehicles reliable on the road.