You may recognize that there is a multitude of engine oil on the shelves out there, and they are all being sold under different vendors. Here’s the thing, there is certainly plenty of dissimilarity between the various types of engine oil depending on their base. But do you know that even seemingly exactly identical engine oil from two different vendors may exhibit vastly contrasting properties? Below is a summary of a comparison between these two oil types done by Project Farm. They are not affiliated with this site be we are a fan of their work so be sure to check them out.
Even if both oils are rated at fully synthetic SAE 5W-30, they can behave entirely different from each other. However, even though there is such a bewildering and eclectic market out there for engine oil, two marques seem to stay on top of the rest: Royal Purple and Amsoil. Therefore, we’ll be comparing two products from their respective lineup, Royal Purple Synthetic 5W-30, and Amsoil Signature Series Synthetic 5W-30.
On paper, both engine oils are premium, fully synthetic engine oil meant for performance applications, or if you’re looking for something that might lengthen your engine’s service life and even service interval. Of course, the premium bit also translates into the price, with the Royal Purple coming in at roughly $10/quart, while the Amsoil comes in at nearly $13/quart.
While both oils are definitely rated to high specifications, the Royal Purple also matches Dexos 2, a GM standard. Intriguingly, the Royal Purple engine oil is genuinely deep purple in color and they guarantee a 1 year/12,000 miles protection. Comparatively, the Amsoil has a normal golden hue, and while it’s similarly rated at 1 year, Amsoil touts a 25,000 miles protection guarantee. That’s definitely a big selling point for those that frequent highways.
Moving to the first test that’s being conducted for both oils, it’s a measure of their overall performance in a condition intended to simulate an engine at a much slower and less intensive scale. This is an all-encompassing test, measuring the oils’ lubricity and retention from normal to high temperature. Providing a rough idea of how both oils will measure up when being cycled in an engine it shows that the Amsoil outperforms the Royal Purple ever so slightly.
The Amsoil manages to provide better wear protection, and this result can be interpreted as the Amsoil boasting a generally better lubricity across the board compared to the Royal Purple. Though the difference seems marginal here when they’re pumped through an engine running at extreme conditions the disparity can widen. That said, both oils definitely performed admirably in the test and will definitely do a good job at lubricating important components in an engine.
Moving on, the next test is a measure of their viscosity in cold conditions. Measured at -15°F, it’s the condition your engine might be expected to shrug off in especially cold climates. Even so, it’s crucial for engine oil to maintain optimum viscosity in the freezing atmosphere since some of the most severe component wear occurs during cold start due to coagulating oil.
And here, it’s apparent that the Amsoil has the upper hand here, flowing considerably better than the Royal Purple while it’s freezing. Again, with that said, both oils are rated to 5W according to SAE standards, so while there is a startling difference between the two, both are plenty capable of handling cold starts.
Following suit is another intriguing test to measure the volatility of the engine oil. This test will determine the tendency for the engine oil to vaporise during extreme operating conditions, such as the surrounding area within your piston rings. This will also demonstrate how oils from the two makes can handle heat cycles, and thus their longevity.
Yet again, Amsoil takes the lead here, losing less of its mass over the duration of the test. This partly explains Amsoil confidence in the ability of the oil to preserve its performance over 25,000 miles. Royal Purple isn’t quite as good, so I wouldn’t doubt its ability at protecting your engine over 12,000 miles.
After heat cycling the engine oil, they will begin to deteriorate somewhat, and it is at this moment where quality engine oil pays off. Vaporised oil will thicken, becoming heavier which contributes to worse engine efficiency and oil consumption. Engine oils are expected to withstand thousands of heat cycles while sustaining ideal lubricity to safeguard your engine from excessive wear.
Amsoil eminently takes the crown here, retaining most of its laudable low-temperature flow characteristics; while the Royal Purple has perceptibly thickened. The Amsoil, markedly, hasn’t become discernibly more viscous, which again stands up to Amsoil’s bold claim.
With this comparison, it’s apparent that Amsoil has manufactured the superior engine oil here – which reflects in its higher price point. It’s not to say that the Royal Purple is in any way shape or form poor. In fact, Royal Purple is very much a beloved brand with its fair share of ardent customers, and they do make excellent products. It’s just that Amsoil has truly formulated an outstanding engine oil here, and relatively speaking, the Royal Purple is slightly inferior. Regardless, if you want a premium engine oil that’ll stand up to performance use, you can’t go wrong with either.