Why Your Fleet Should Consider 5W-30 Over 10W-40 Engine Oil

At Millers Oils, we understand the pressures fleet operators face when balancing performance and cost, and one critical factor? The right engine oil. It’s tempting to look at lubricant choices through the lens of unit price, especially when 10W-40 appears cheaper than 5W-30.

But here’s the reality… oil isn’t just a consumable, it’s a critical engine component. Choosing Truckmaster 5W-30 over 10W-40 isn’t just a spec decision, it’s a strategic move for lower total cost of ownership, and improved fuel economy.

Let’s break down why 5W-30 might be a smarter choice than 10W-40 for modern fleets:

 Fuel Economy That Pays Off

Compared to 10W-40, 5W-30 is a lower viscosity oil. This allows it to flow more easily at cold starts and operating temperature, reducing internal friction and enabling the engine to operate more efficiently, especially during steady-load driving.

Operators using Truckmaster 5W-30 typically see fuel savings of 1–3%, depending on the engine type and duty cycle. Across an entire heavy-duty fleet, these savings can quickly outweigh the upfront cost difference between 5W-30 and 10W-40.

The bottom line? Choosing the right oil (not just based on specification, but tailored to your fleet and requirements) leads to long-term fuel efficiency gains and real reductions in one of your fleet’s highest operating costs.

Superior Cold-Start Protection

Engine Oils with lower “W” (winter) rating like Truckmaster 5W-30, flow more quickly when the engine is cold, meaning that a 5W-30 circulates faster than a 10W-40. This rapid oil flow is critical during cold starts, which are one of the most inefficient and high-wear periods for any engine. In fact, up to 70–80% of engine wear occurs at start-up.

For vehicles in cold or variable climates, or fleets operating under stop-start driving conditions, this quick response offers significant protection.

• Faster oil circulation = Quicker protection of moving parts
• Lower start up resistance = Less battery strain and easier cranking
• Reduced wear = Longer engine life and lower rebuild costs

The result? Better protection when your engine needs it most.

Extended Drain Intervals, Less Downtime

Truckmaster 5W-30 is engineered for the harshest conditions, and designed to go the distance. Its advanced additive package resists oxidation and maintains viscosity over time, which translates to:

• Fewer oil changes
• Reduced maintenance related downtime
• Lower labour and disposal costs

While 10W-40 remains a competent lubricant, it may have shorter drain capabilities, and as a result, any upfront cost savings can quickly be offset by more frequent servicing and associated expenses.

Futureproofing Your Fleet

At face value, 10W-40 may seem like the more cost-effective option with a cheaper cost per litre. But once you consider the bigger picture of fuel savings, reduced maintenance and OEM compliance, the true cost of sticking with 10W-40 can be far higher. You risk sacrificing long-term savings for short-term gain, and in a fleet environment, that’s a poor trade.

As engine technology advances, 5W-30 is increasingly becoming the standard recommendation across commercial vehicle manufacturers. Making the switch now helps you not only optimise performance, but also streamline oil usage across mixed fleets, making inventory management and servicing simpler and more efficient.

Choose Truckmaster 5W-30

Truckmaster 5W-30 is the solution for long-term performance, protection, and profitability for your fleet. Need help comparing lifecycle cost models or transitioning your fleet? Speak to our Technical Support Team or explore the benefits of Truckmaster 5W-30 here.

Read more about choosing the right engine oil for your fleet here.