Inside the Motor Oil Geek’s Epic 8-Oil Test: What Shear, Heat, Power, and Contamination Really Tell Us

Lake Speed Jr.’s Motor Oil Geek channel has become a rare place on the internet where tribology — the science of friction, wear, and lubrication — is treated seriously without being treated solemnly. In this deep-dive session, Speed Jr. is joined by Chip Hewette, recently retired from Afton Chemical, to unpack results from an extensive eight-oil lab and engine dyno test and then connect those findings to real-world data from the SPEEDiagnostix used-oil database.

The result is not a brand shootout or a list of winners and losers. It is something far more useful: a framework for understanding how oil formulation choices affect shear stability, oxidation resistance, deposits, engine temperature, power, and long-term wear — and how those effects show up in real engines over time.

Who’s in the room, and why it matters

Chip Hewette brings more than two decades of experience from inside one of the four major global additive suppliers. In the lubricant industry, most finished motor oils rely on additive packages from a very small group of companies — Lubrizol, Afton Chemical, Chevron Oronite, and Infineum. Hewette spent his career designing and evaluating those packages, working on engine oils, gear oils, and transmission fluids across OEM and motorsports applications.

Now working with SPEEDiagnostix, Hewette is helping mine a growing database of over 11,000 used-oil samples to extract patterns that individual oil reports can never reveal on their own.

Speed Jr. is explicit about the goal: remove marketing pressure, use controlled testing, and build knowledge that actually helps people make better decisions about engines they want to last.

Why this eight-oil test is different

The lab and dyno work discussed in the video is built on a test platform Speed Jr. has used for years in oil development. The engine, components, and procedures are intentionally consistent so small differences can be detected with confidence. That matters, because when testing lacks repeatability, people end up arguing about noise instead of signal.

The team also acknowledges a practical reality: no independent channel can afford to run every possible ASTM and OEM test. Instead, they selected a focused group of tests that reveal meaningful tradeoffs in real engines:

• Viscosity and viscosity index
• Shear stability under load
• Oxidation resistance
• Deposit tendency
• Engine dyno measurements of torque, power, oil temperature, and oil pressure

Each test answers a different question about durability, efficiency, or performance.

Viscosity: the label hides a range, not a point

All eight oils in the test carry the same viscosity grade on the bottle, but that grade represents a window, not a single number. At operating temperature (100°C), some oils start near the low end of the allowed range while others sit higher.

That choice is intentional. Formulators may target the low end to help fuel economy claims, or the higher end to support durability under heat and load. The consumer takeaway is simple but important: two oils with the same label can behave very differently before the engine ever turns a crank.

Shear stability: what happens after the oil gets worked

Multi-grade oils rely on viscosity index improvers — polymers that expand and contract with temperature. Those polymers are forced through extremely tight clearances in engines and can be mechanically sheared, permanently reducing viscosity.

To study this, the team used a KRL shear test, specifically a shorter 15-minute version that Speed Jr. says correlates well with what SPEEDiagnostix sees in real used-oil samples sent in for used oil analysis. Some oils retained their viscosity remarkably well. Others dropped to the bottom of the grade or even out of grade entirely.

The message is not subtle: an oil that starts in grade but does not stay there can become a liability, especially under sustained load or long drain intervals.

Polymer chemistry matters more than most people realize

Hewette and Speed Jr. emphasize that not all viscosity index improvers behave the same. Polymer type, molecular size, and chemistry determine how easily those molecules are cut under shear.

Two oils can meet the same specification while relying on very different polymer strategies, and those strategies can produce very different outcomes once the oil is in service. This is one reason why “meets spec” does not guarantee identical performance in the engine.

Oxidation resistance: durability has a time limit

Oxidation stability was evaluated using Pressure Differential Scanning Calorimetry (PDSC), an accelerated test that measures how long an oil resists oxidative breakdown under heat and oxygen.

The results showed dramatic variation between oils. Some resisted oxidation for much longer than others.

Speed Jr. highlights a critical formulation tradeoff: components that excel at friction reduction are not always strong performers in oxidation stability. Lubricant formulation is a balancing act, not a search for a perfect ingredient that does everything well.

Oxidation matters because once it accelerates, oil properties change rapidly — additives deplete, deposits form, viscosity shifts, and wear protection can deteriorate.

Deposits: when friction modifiers have consequences

High-temperature deposit testing revealed large differences among the oils. Oils with high treat rates of certain friction modifiers, particularly molybdenum-containing compounds, tended to show higher deposit formation.

Hewette adds an important nuance: “moly” is a shorthand label. Many molybdenum compounds include sulfur, and sulfur-containing chemistries can be highly reactive at elevated temperatures. That reactivity can contribute to deposit formation.

This is not an argument against molybdenum. It is a reminder that chemistry, dosage, and the rest of the formulation determine outcomes. More additive is not automatically better.

Ranking oils without pretending there’s one right answer

Hewette demonstrates a simple ranking approach: score each oil across several metrics and apply weights based on what matters most. In his example, deposit control and oxidation resistance rank highest because they relate directly to durability. Shear stability follows closely. Viscosity index ranks lower because it is more closely tied to fuel economy than long-term protection.

He is careful to stress that this is not “the” answer. It is a way of thinking — one that encourages consumers to decide what they value and evaluate oils accordingly.

Dyno results: yes, oil can change power and torque

The engine dyno results confirm something enthusiasts often debate: oil formulation can influence performance.

Across the eight oils, the torque spread was about 1.6% from lowest to highest. That may sound small, but in engineering terms it is meaningful. Gains of one or two percent are taken seriously in professional motorsports and can be felt in real vehicles.

Just as important, this establishes a reality check. Claims of five or ten percent power gains from oil alone are not credible.

Why power and torque don’t rank the same way

Torque and horsepower are related but not identical. Horsepower includes engine speed, so oils that perform well near peak torque do not necessarily rank the same at peak power RPM.

At higher speeds, frictional and pumping losses change, and formulation differences become more apparent. Oils that achieve power gains by allowing viscosity to shear may look impressive on a peak chart while quietly sacrificing protection.

Oil temperature: the most surprising result

One of the most striking findings in the dyno data is oil temperature. Under identical conditions, oil temperature varied by roughly 12% between the coolest-running and hottest-running oils.

This matters because temperature affects viscosity, oil pressure, and film thickness. Oils that shed heat more effectively maintain viscosity and pressure more consistently, while hotter-running oils thin out and can lose protective margin.

Hewette explains that heat transfer properties depend on base oil structure and polymer chemistry. Different molecular shapes conduct heat differently, and those differences show up clearly on the dyno.

Oil pressure: same grade, different reality

Oil pressure also varied significantly across the oils. This reinforces a key theme of the entire discussion: the engine does not experience the viscosity printed on the bottle. It experiences the viscosity that remains after shear and at the temperature the oil actually runs.

An oil that runs cooler may maintain higher effective viscosity and pressure even if its nominal grade is the same as a hotter-running competitor.

Putting it all together: pressure up, temperature down

A combined plot of torque, power, oil temperature, and oil pressure reveals a consistent pattern. Higher torque and power align with lower oil temperature and higher oil pressure. Lower performance aligns with higher temperature and lower pressure.

Hewette summarizes it plainly:

• High pressure and low temperature support thicker protective films, lower resistance to motion, and better heat transfer.
• Low pressure and high temperature reduce film thickness, increase resistance, and trap heat.

The oil that produces power by sacrificing viscosity may look good briefly, but the conditions it creates inside the engine are not ideal for longevity.

What the SPEEDiagnostix database reveals about real engines

The second half of the discussion shifts from controlled testing to real-world behavior using over 11,000 used-oil samples and approximately 1,200 particle count tests.

Break-in wear lasts longer than most people think

Data partitioned by odometer mileage shows dramatically higher wear rates below roughly 5,000 miles. This challenges the common belief that engine break-in ends at 500 or 1,000 miles.

The implication is critical for oil analysis: changing brands or viscosities during early break-in makes it impossible to draw meaningful conclusions. Break-in wear overwhelms formulation differences until the engine stabilizes.

Outside contamination hits new engines hardest

Silicon is used as a proxy for outside contamination such as dust ingestion. The data shows that in newer engines, elevated silicon correlates with dramatically higher wear. Older engines are more tolerant, but contamination still increases wear.

The practical advice is blunt: avoid modifications that increase dirt ingestion on new engines. Filtration matters most early in life.

Particle count reveals what elemental analysis cannot

Standard spectrometric oil analysis only detects relatively small particles. Particle counting captures larger debris that can still cause damage.

Looking at particles ≥38 microns, Hewette shows that in newer engines, even modest particle counts correspond to much higher wear rates. As engines age and stabilize, tolerance improves, but the relationship remains.

This explains why early oil changes are effective even when the oil “looks fine.” It is about removing abrasive debris before it circulates.

Practical takeaways that don’t require brand loyalty

The session ends with guidance that is refreshingly conservative:

• Use the OEM-specified oil in new engines. Focus on sensible early oil change intervals rather than experimenting with chemistry.
• Avoid aftermarket oil additives. Finished oils are balanced systems, and random additions can create unintended consequences.
• If using oil analysis, stick with one lab to maintain consistent trending.
• Control contamination early through good filtration and reasonable service intervals.
• Evaluate oils holistically — shear stability, temperature behavior, pressure, and durability — not just peak power numbers.

The real lesson

This eight-oil test and the accompanying data analysis do not crown a universal winner. Instead, they expose the complexity hiding behind simple labels and marketing claims.

Oil performance is about tradeoffs. Staying in grade matters. Heat management matters. Contamination control matters — especially early in an engine’s life.

If the goal is a long-lived, reliable engine, the smartest strategy is not chasing magic bottles. It is understanding the system, respecting break-in, and choosing oils based on how they actually behave once the engine is doing real work.