Is Synthetic Motor Oil Better than Conventional?

AMSOIL synthetic motor oilYes. Test data repeatedly shows that synthetic motor oil outperforms conventional oil, delivering…

  • Improved wear protection
  • Better extreme-temperature performance
  • Maximum fuel economy
  • Longer service intervals

Some of you are undoubtedly thinking, “But I’ve used conventional oil for years, and my engine runs fine.”

It’s important to note I didn’t say all conventional oil is junk that will wreck your engine; I simply said synthetic motor oil offers better protection and performance.

Back in 2007, AMSOIL introduced a Comparative Motor Oil Test that pitted AMSOIL 10W-30 Synthetic Motor Oil against several synthetic and conventional oils. You’ll notice the synthetic oils offer improved protection against wear and high-temperature evaporation, along with easier cold starts, compared to the conventional oils.

We updated the test in 2009, and the results again favored the synthetic oils. You don’t have to take our word for it; simply Google “Is synthetic oil better?” and you’ll find all kinds of supporting information.

Why does it matter to me?

Even so, maybe you’ve been using conventional oil for years and you’re happy with the results. That’s great. It’s still a free country – continue to use it.

But if you’re thinking about upgrading to synthetic oil, here are a couple points that may influence your decision.

Modern engines are tougher on oil 

To keep pace with fuel-economy and emissions mandates, automakers are designing engines with turbochargers, direct fuel injection and variable valve timing (VVT) to help meet regulations without sacrificing power or torque. These advancements result in hotter operating temperatures that can quickly break down the oil and cause oxidation, sludge and deposits.

Turbo Glows Red Hot
Turbo glowing red-hot.

Beware of fuel dilution

In some direct-fuel-injected vehicles, we’ve seen high rates of fuel dilution. During operation, fuel can wash past the piston rings and contaminate the motor oil, causing it to lose viscosity. Thinner oil may not provide the wear protection your engine needs. Plus, excessive fuel dilution requires the oil to be changed more often.

Oil cleanliness is vital

Although engines with VVT deliver improved efficiency, they use finely engineered components that require clean oil to function properly. Otherwise deposits can clog the tiny oil-flow passages and trigger your check-engine light.

Synthetics’ improved resistance to extreme heat and viscosity loss make them the better choice in today’s sophisticated engines.

For these reasons, a number of automakers recommend synthetic oil in their vehicles, including newer GM, Toyota and European vehicles. As engines continue to push the limits of performance, that list will likely grow in the years ahead.

Whichever oil you choose, make sure it meets the recommendations given in your vehicle owner’s manual.


  1. synthetic motor oil is far better in performance and mileage than the conventional motor oil. There is much difference between conventional and synthetic motor oil. Conventional motor oil is a lubricant that is derivative directly from crude oil. … Improved Lubrication – Best synthetic oils have added lubricants that increase the ability of the oil to keep engine parts slick, especially at high temperatures. This decreases wear over the long term, and may make your engine last longer.

  2. This article forgot to mention that you can switch from a conventional motor oil to synthetic anytime without affecting the engine components. If you use conventional oils and switch to synthetics, the synthetic oil will clean the deposits left behind from conventional oils and become darker sooner. I had a 1989 Bonneville SSE with over 450,000 miles on the original engine and transmission. The engine and tranny performed like new when I sold it due to Midwest salted roads. The engine and tranny were never torn down for rebuild, so everything was the same as it came from GM except the valve guide seals, which wore out every 100,000 miles. The internal engine parts below the valve covers were spotless, no deposits whatsoever. I use synthetic oil in every engine I own and have never experienced any mechanical issues caused from the oil. Another important factor to consider is that it is actually cheaper to use synthetic oils over conventional because you can extend the service change interval to the actual service requirements instead of every 3000 miles.

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