THE SLIPPERY TRUTH: SYNTHETIC ENGINE OILS VS CONVENTIONAL

Treat a truck right, and it will reward you with many years of faithful service. And if there’s one thing you can do to maximise a vehicle’s shelf-life, it’s stick to your oil change schedule. Regular fresh oil will keep your truck running like – well – like a well-oiled machine. But when it comes to protecting your engine’s inner workings, not all oils were created equal. At one end of the scale, there are budget-level conventional oils. At the other: high-tech premium synthetics. Synthetic engine oils are designed to out-perform conventional ones, from protecting against engine wear and corrosion, to removing sludgy deposits, improving efficiency and lowering fuel consumption. When oil change time comes around, it’s worth understanding what makes a premium synthetic oil worth the higher sticker price – how it can maximise your truck's engine life and reliability while simultaneously reducing your fuel bills. Read on as we delve into the difference between conventional and synthetic oils, and separate truth from urban myth.

Spot the difference

All conventional engine oils, and many synthetic ones, are made from crude oil. The key difference between the two is that while conventional engine oils undergo basic refining, synthetic oils are submitted to several further purification and processing steps, removing impurities that can impair their performance. Alternatively, synthetic oils can also be created – from the atoms up – from natural gas, which means they never contain crude oil’s impurities in the first place. Whatever the production method, the highly refined nature of synthetic oils means they offer inherently better engine protection properties compared to conventional oil. Take viscosity, for example – how thick and treacly an oil is. Synthetic oils flow better at low temperatures than their conventional counterparts, meaning they coat vulnerable engine parts much quicker when the engine is started cold. A better-lubricated engine also uses less fuel, so synthetic oils can help cut fuel costs.

Aging gracefully

Over time, the performance difference between conventional and synthetic oils gets greater and greater. Conventional oils include additives that help improve their viscosity, but these additives gradually break down, meaning conventional oils become thicker and thicker when cold. By the time you’re due for a change, a conventional oil will be far less protective of a cold engine. Because synthetic oils’ better viscosity is down to the basic properties, rather than an additive, they retain their excellent flow properties right up to oil change time. They also protect hot engines better. As conventional oil additives break down, the oil can become too thin to be fully protective at high temperatures, especially in stop-start city traffic and during the heat of summer.

Slick operator

Engine oils do more than simply ensure moving parts glide smoothly past each other. They also assist cooling by helping to carry heat away from hot internal components. That’s particularly important in modern turbo diesel truck engines, where the turbo operates at very high temperatures. The additional purification steps that go into creating a synthetic oil remove the sulfur impurities and waxes present in conventional oil, which can break down at very high temperatures and form gunky deposits that restrict oil flow around the engine. Truck turbochargers have been known to fail after becoming choked by deposits formed by conventional oil breakdown. As well as being unlikely to generate sludge, synthetic oils also include additives designed to break down and remove these deposits. Further additives mop up corrosive by-products of fuel combustion that would otherwise attack metal components and rubber seals.

Hit or myth?

Urban legend will tell you that conventional and synthetic engine oils must never be mixed and that, once you’ve switched to a synthetic, you can never go back. In truth, the two will happily mingle. You can even buy conventional/synthetic oil blends right off the shelf as intermediate-performance engine oils. Drivers can switch from conventional to synthetic oil, and back again, from one oil change to the next, or even top up their oil levels with one kind or the other between services. Another myth, equally false, is that synthetic oils can damage engine seals and cause oil leaks. In fact, synthetic oils contain additives designed to recondition and restore engine seals.

Fresh oil frequency

How often does a truck’s oil need changing? That varies from truck to truck. Every engine is designed with a specific oil change frequency and viscosity in mind. From early 2016, all Isuzu trucks with Allison transmissions will be supplied from our factory with a synthetic transmission oil, resulting in an oil change interval up to six times longer than that for mineral oil. To find out which synthetic oil type is best for your truck – and how often it should be changed – check your owner’s manual, ask your dealer or mechanic, or try this online guide.