Vehicles with high-mileage typically suffer from more wear and tear. Increased engine wear often results in oil leaks, sludge and deposit build-up within the engine’s inner workings. Polymer seals and rings also degenerate over time, resulting in less efficient seals and a need for replacement.

However, other factors also influence the rate of engine wear, such as where the car is being driven. For example, highway miles are easier on the engine than city driving because of the frequent stop and acceleration cycles. Driver style, habits and vehicle maintenance also affect the rate of wear on a vehicle’s engine.

The impact of high-mileage on a vehicle will vary depending on its service history, oil changes, owner’s driving style along with the quality of the lubricants and fuel that the car consumes. The most noticeable challenge that vehicle owners face is the decline in engine performance, diminished power and overall, a less responsive vehicle.

As the miles accumulate, there is an increased potential for poor ring sealing in the piston-liner interface caused by soot and deposits from incomplete combustion and wear over time. This can result in engine blow-by as combustion gasses are pushed past the piston rings and into the crankcase. When this loss of compression occurs, it has a negative impact on horsepower and fuel economy.

A high-mileage engine can benefit from an oil specifically designed to protect a "well-travelled engine", one that will keep the vehicle running at top performance no matter its age.

Engine oils that have been developed specifically for high-mileage engines can help restore the performance and efficiency of the engine. These oils could contain unique additives to reduce sludge and deposit build-up within the engine and promote engine durability. These carefully balanced lubricants offer older engines added protection to help prevent further deposit formation and improve engine reliability.

In addition, high-mileage engine oils can help maintain engine compression with reduced blow-by to provide the driver with more power.

There is a common myth that vehicles with higher mileage need a higher viscosity (or thicker) engine oil to protect the engine’s inner workings. This is not the case – the engine oil used should always be as recommended within the Original Equipment Manufacturer (OEM) manual.

Vehicles that have higher mileage should use a specialty high-mileage engine oil that has been designed to offer protection for well-travelled engines and to improve engine performance. The engine oil should still be aligned with the viscosity grades recommended by the OEM. As for newer vehicles that may still be under warranty, if an incorrect viscosity grade is selected and used, the warranty could be voided.

High-mileage oils fulfill a more complicated role and therefore have a more complex and unique additive system to help protect and restore the engine’s performance and efficiency. The benefits are extensive, including helping to prevent breakdowns and expensive maintenance costs to keep the vehicle on the road even longer. The reality is that a high-mileage oil is a cost-effective solution to help prevent regular trips to a mechanic, ultimately saving the owner money.

Before recommending a high-mileage engine oil, it is important to first check that the vehicle does have a high number of miles. The level of what is now perceived as high-mileage has increased in the last decade, but awareness amongst consumers varies drastically, so this should always be the first question: how many miles or kilometers has your vehicle covered?

Once it is confirmed that the vehicle has travelled more than 120,000 kilometers, the next step is to consult the OEM manual for the recommended oil viscosity and performance level. This should always determine the oil selection, so that an appropriate high-mileage oil can be selected to help restore the engine’s efficiency and ensure its overall protection.