Is Thinner the Winner? Low Viscosity Engine Oil Runs the Gauntlet

Remember when engine oil was as crude as, well… crude? An era when most run-of-the-mill engines still sported more than four pistons, and excessive piston ring blow-by was considered just a smoky side-effect of the internal engine combustion process. Fuel efficiency fears? Gas was flowing at 84 cents a gallon. EPA constraints? Got a catalytic converter and you’re golden.

Nowadays, things are very different, especially when it comes to average commuter cars. Smaller engines running on high compression or forced induction have become the norm. Environmental regulations abound, restricting everything from exhaust port outputs to fuel efficiency stickers, thus forcing automakers to seek new ways to make their motors perform more cleanly and efficiently.

Amongst a multitude of other modifications, this has led to the widespread usage of low-viscosity engine oil. As opposed to older engines, newer motors typically have tighter tolerances between engine parts, and automakers claim that in order to operate more efficiently, a thinner lubricant is required.

But does lower-viscosity motor oil offer the same level of protection against engine wear? How does a thinner engine oil perform in regard to thermal breakdown and evaporation? What about long-term reliability?

A little while back, Todd over at Project Farm decided to put thinner oil products to the test in his usual way, to see how they held up in comparison to their “average weight” alternatives. Lighter oil viscosity means that the oil is more free-flowing and therefore reduces resistance, right? Or is there something else going on behind the oily scenes that we just can’t see? Something far more… detrimental. 

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Todd is quick to point out the fact that the “W” on a bottle of engine oil does not refer to its weight, but refers to the word “winter” instead. Photo Credit: Project Farm/YouTube

The Lubed-Up Lineup

The products purchased for testing in Project Farm’s video were all pulled from the Pennzoil portfolio. All of these oils were refined from natural gas, and claim to be “carbon neutral.”

Furthermore, all of the oils tested were Platinum Full-Synthetic variants, and API SP certified. The four light viscosity options tested included:

Running The Gauntlet

Viscosity levels (both at room temp and in cold environments), engine wear results, and high-temp abuse were all considered during Todd’s testing procedures. He also examined all of the ingredients within each synthetic oil to determine which product looked the most beneficial on paper.

To do so, Todd spent the dough and had samples of all four oils shipped off to an independent testing facility in Fort Wayne, IN called Blackstone Laboratories. Since it never hurts to have an unbiased third-party report on a subject, this report covers the basics in clear-cut fashion: Anti-wear capabilities, detergent levels, and a total base number for each engine oil weight being to top considerations.

For the gravity viscosity test, none of the oils were tested at maximum operating temps, with Todd opting to test things around room temp instead.

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Photo Credit: Project Farm/YouTube

This was followed by a high-temp “engine test,” which was conducted with a couple of coffee pots and some hot plates. Temps were set to 410°F for two hours, with regular rotations between electric eyes being conducted for quality control purposes. After two hours of continuous heat, each coffee pot was weighed once more, thus illuminating any evaporation loss.

After completing the evaporation stage, the heat-treated oils were subjected to a friction test, where a wheel and a grinding pin could clearly illustrate how well each oil coated and protected raw metal materials. This was paired with a second gravity viscosity test, to see how each heat-treated engine oil performed post-high-temp exposure.

As for cold testing, that was conducted after a 12-hour stint in a freezer that was set to -40°F. This was followed by a cold oil gravity performance test, just for those northerners in the audience who were wondering if low-viscosity engine oils make a difference in winter.

Results, Risks, and a Really Good Recommendation

As expected, the 5W-30 was the slowest-moving contender during the room-temperature gravity test, with the 0W-16 easily being the fastest down the “lube luge.” Interestingly, both the Pennzoil 0W-20 and the 5W-20 products were nearly identical in their performance. Keep in mind here, we would expect room temperature to show more disparity between the multigrade viscosities.

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Photo Credit: Project Farm/YouTube

As for the heat test, that was a bit of a mixed bag as well. After less than twenty minutes of heat, the 0W-16 had turned very opaque and had boiled down quite a bit, whereas the 5W-30 appeared to be unfazed, at least in color. While both oils experienced evaporation loss, the 5W-30 faired a bit better and did not burn off nearly as much. Like the first viscosity test, the 0W-20 versus 5W-20 heat treatment comparison was almost too close to call.

All told, oil film strength during the friction test resulted in the 5W-30 having an 8-percent smaller wear scar over the 0W-16 engine oil. Meanwhile, the 5W-20 had about a 7-percent smaller wear scar after wear resistance testing was complete than the 0W-20 motor oil. So a major win for the heavier oils in this regard.

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The post-heating oil-flow tests provided some interesting results. Photo Credit: Project Farm/YouTube

Unheated, cold gravity viscosity testing resulted in the 0W-16 being the only liquid light enough to escape the test tube immediately, with the rest requiring around 45 seconds of warm-up time. From there, the rest of the oils slid down in ascending order, with the 5W-30 landing last. Odd considering two 0-weight winter grades were being tested. 

In contrast, when the oils were exposed to prolonged periods of high heat, all of the oils performed far more sluggishly. This resulted in all four products retaining the same order as before when crossing the finishing line, all be it at a much slower pace.

As for ingredients, the 0W-16 was the clear winner here, with a chemical composition that was quite more all-encompassing than the other oils. That being said, Todd suggests following the automaker’s recommended motor oil viscosity for whatever vehicle you daily drive. A statement that we tend to agree with. Make sure to watch the video for all of the graphs and charts of the testing results. 

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When an auto manufacturer recommends a specific oil type and viscosity, they have damn good reason for such a suggestion. They don’t want lower MPG ratings, EPA investigations, or recalls. Automaker engineering teams test a ton of different oil viscosities until they settle on one that works best. Photo Credit: Project Farm/YouTube

Some Closing Engine Oil Considerations

After perusing the slew of reader comments labeled beneath this comparison test video, a few considerations caught our eye. All of which we have mildly edited, and streamlined for digestibility’s sake below. Take a look, because these are indeed quite valid points.

One of the top comments had to do with variable valve timing, or VVT. These systems almost always require a thinner engine oil. While some people claim that this is because lighter oil flows more freely (even in colder temperatures), thus keeping those VVT hydraulic actuators running smoothly, another modern addition to automobiles should be taken into account as well. Many newer cars come with an oil cooler for viscosity and evaporation control, so in warmer weather, there is at least some relief from the heat in that regard.

Ultimately, it comes down to following the manufacturer’s recommendation on oil viscosity. Photo Credit: Project Farm/YouTube

Another viewer commented on the fact that most high-compression and forced induction engines are commonly coupled with direct injection. Their concern was that the use of thinner motor oils in these types of engines can cause intake ports to be prematurely contaminated by blow-by. Naturally, contamination within the oil itself is a worry as well, especially when temps spike in summer.

So while motor oils are far lighter and loaded with more beneficial additives than ever before, one core question remains: Do low-viscosity engine oils help or hurt the longevity of modern powerplants? Some say that only time will tell, while others claim that these lightweight lubricants are already causing catastrophic failure inside and we don’t even know it. We have to side with the manufacturers on this one, as ultimately, no one benefits from requiring an inferior product, where a warranty is involved. So as long as the engine is designed for it, the performance of thinner modern oils shouldn’t concern you. 

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Photo Credit: Project Farm/YouTube

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Micah Wright

Raised on LEGOs by grandfathers who insisted on fixing everything themselves, Micah has been a petrolhead in training since age four. His favorite past times include craft beer, strong cigars, fast cars, and culinary creativity in all of its forms.
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