Debunked: 5 Common Myths About Synthetic Diesel Oil

Switching back to conventional oil from synthetic is absolutely safe. You can change from the 5W-40 synthetic oil you used in the winter to a 15W-40 conventional oil in the spring. We offer Shell Rotella T4 15W-40 conventional oil and Shell Rotella T6 15W-40 full synthetic if you want the added benefits of synthetic oil technology.

“During colder months, it's a good idea to switch to a lower viscosity oil – in this case, synthetic oil – to provide improvements in engine stability,” explains Karin Haumann, OEM Technical Manager for Shell Lubricants.

Haumann adds: “Because a synthetic oil can meet the same OEM specification as a conventional oil, the question is, are you willing to relinquish the inherent benefits a full synthetic product can give you?” With the proven benefits of synthetic, you can use it in your engine all the time.

The truth is that whether or not the price is too high is relative to the buyer, of course. However, Shell knows that the higher cost of synthetic oil is worth the investment.

“The benefits of Shell Rotella^® synthetic motor oil – you may not see them when paying at the store register. But what we've seen in terms of the potential our oils give in terms of protection, longer oil drain intervals and equipment life over the lifetime of the engine easily outweigh the cost,” assures Jason.

Synthetic engine oils are designed to provide improved protection for a range of extreme working conditions. Whether you’re stop-and-go driving or working in freezing cold or desert heat, synthetic engine oils are designed to:

• Protect your engine
• Clean your engine
• Cool your engine
• Lubricate the engine

If your engine is designed for higher performance, of course that's putting higher stress on the engine and the oil. So you'd want to have an oil that's better at withstanding that stress.

“It’s well known that synthetic products can do that better than conventional oils,” says Dan. “Most new vehicles require a -50 or lower synthetic blend type oil because it improves startability in heavy-duty engines and offers real advantages in fuel economy.”

Switching from an oil that meets API CK-4 industry standards to a Shell Rotella^® CK-4 product has nothing to do with the brand of oil and everything to do with the specification and approval of the oil. If bottles have the same specs (meaning API industry standard), you can move between brands.

But because you can switch this doesn’t address the fact that not all oils are created the same. Even though oils may meet the same industry and OEM specifications, they can and often do, have different performance levels.

Think a 10W-30 oil can't provide the same protection as a 15W-40? “Shell has millions of miles of field tests demonstrating equivalent wear performance between Shell 15W-40 engine oils and Shell 5W-30 or 10W-30 products.

Crucially, our 5W-30 and 10W-30 products also offer fuel economy benefits. So moving to a reduced semi-synthetic 10W-30 or a full synthetic 5W-30 provides the standard wear protection of a 15W-40 with the added benefit of fuel savings.

In addition, most of the heavy-duty engine manufacturers have been factory-filling their engines with an SAE 10W-30 since 2013, and for some since 2010.

Shell Rotella^® offers both a 15W-40 synthetic blend and a full synthetic option for diesel engine drivers that prefer to stick with higher-viscosity oils but still get the benefits of synthetic technology.