What Separates a Racing Oil From a Street Oil?

Race Oils: Designed for High-Temperature and High-Shear Situations

First, that big question: What exactly separates a race oil from the typical oil found in passenger cars? 

We asked someone who knows: Alec Wolff, technical product manager at Motul. And before joining the oil company, he spent years in the pits of IMSA and SCCA races. 

“Racing oil is designed with a specific intent and to be used under a limited scope of operation,” he explains. “Basically, it’s designed to always be under stress and dealing with a lot of heat and a lot of shear forces and a lot of rpm. 

“Typical service oils have far different demands,” he continues. “First, they need to have a very long service life, and they deal with much different stresses than racing oils. A race engine is rarely going to be started up and not properly brought to temperature and run hard for a while. Street engines see that kind of use all the time.”

His takeaway message: “It really comes down to designing an oil to excel under a limited set of circumstances.”

He compares race oil to race tires: “They produce a ton of grip and deal with heat well and wear a certain way when under stress, but you wouldn’t want to commute on them during winter.”

In the case of Motul, the brand’s 300V line is solely aimed at those heading to the track–again, just like race tires. 

A characteristic that makes an engine oil better suited for the track is high shear strength. “Shear strength is a huge key with racing oil,” Wolff explains. “The key is you want to maintain a film of oil between metal surfaces, obviously. It’s easy to do that if the oil is really thick, but you have to run bigger tolerances in the engine, and you lose real power to parasitic drag moving that thick oil around.”

Tightening up those tolerances puts more demands on the oil. “So, you want to run as low viscosity an oil as you can to cut the parasitic drag,” he continues, “but also to make that layer of lubrication between surfaces very thin, so you can have more precise tolerances. When you’re running things that tight, shear strength is a huge consideration, because the oil needs to maintain its structure to keep providing that barrier between metals.”

The ester bases found in a race oil provide that excellent shear strength, but they also have other inherent chemical properties that make them a good start for a high-load oil. The actual polarity of ester molecules attracts them to negatively charged metal surfaces, which serves to further enhance the stability of the microscopic layer of liquid lubrication between surfaces.

Of course, there are limitations to oils designed for such a specific set of circumstances. “Probably the biggest functional difference outside of performance for a race oil versus a street oil is service life,” Wolff explains. “Street oils are designed with such long service lives these days. They have to deal with thousands of miles and many months of contaminants, highly variable temperatures, moisture levels, different blends of gas just lots and lots of variables.”

A race oil, he continues, can concentrate on a narrow mission: “With a race oil like 300V with EsterCore Technology, we don’t have to worry about a lot of those factors and can focus strictly on high-load performance.”

Indeed, most oils designed for street use are also certified by various regulatory bodies. These oil manufacturers are forced to meet standards of international transportation regulatory agencies, auto manufacturers, and environmental agencies. 

While all of those regulations can certainly show that the oil meets definite, objective standards, they also tend to turn most modern street oils into jacks of all trades and masters of none. That’s fantastic for a commuter car that only needs an oil change every 8000 miles or more, but it’s less ideal for a dedicated track weapon. Race oils deigned for off-highway use don’t need to conform to those international standards, so they can be highly specifically formulated to meet the needs of competitors.

So, who exactly needs these specially formulated race oils, and who can get by with a high-quality service oil? Wolff breaks it down based on how the car is used. 

“If you’re talking about an unmodified car that’s mostly used for regular driving but sees the occasional weekend autocross or even track day, you’re probably best off with a 100% synthetic, street-spec oil,” he explains. “A street oil will have an easier time dealing with occasional hard use than a race oil will have dealing with frequent light use.

“Now,” he continues, “if you’re talking about a car that gets trailered to the track, driven hard, then put away until the next track use, yeah, you’re definitely looking at a race oil application. 

“The tricky ones are the in-between cars–the ones that maybe get driven to the track and run all weekend but mostly sit in the garage aside from that. Or the ones with modified engines that put more thermal stress on the oil. Or the ones that are built to tighter tolerances than the factory may have. In those cases, we recommend that if owners are going to run a race oil like 300V, there’s nothing wrong with that, just stick to an aggressive replacement schedule, like every 3000 miles or less.”

Race Oils: Designed From the Molecules Up

High-end racing oils like 300V are basically built from scratch using bespoke, designer ester molecules–those esters mentioned previously. Esters encompass a broad class of chemicals that are essentially byproducts of another chemical reaction: the combination of an alcohol and an acid. (Motul notes that they have their own ester-based technology called EsterCore.)

Of course, the specific formulation of the esters used to produce a race oil is a closely guarded secret. But the big thing about esters in general is that they can be produced by a wide range of chemical combinations. And all of these combinations result in an ester base with different properties. 

Then there’s the additive package that is mixed in to create a final product–again, fine-tuning the oil for the specific mission.

Race Oils Are Built to Endure Actual Racing

In addition to working with several race teams–both ones that use leased or sealed engines from factory racing programs and ones that build their own engines–Motul performs in-house testing in a controlled environment to gather data. 

Motul uses dyno-based simulations that run an engine through a preprogrammed use pattern over a set period of time, Wolff explains. In fact, one of the company’s go-to tests is a simulation of the 24 Hours of Le Mans. During that single test, the engine is accelerated and decelerated against a load that duplicates repeated laps of Le Mans. A fully gimballed dyno rig even tilts and leans the engine to simulate g-loads experienced during cornering, acceleration and braking. 

Data is captured constantly, in real time, throughout the test cycle, and Motul shared some test data gathered on a Porsche GT3-spec engine. After an initial horsepower bump thanks to the break-in process, the dyno shows constant numbers throughout the balance of the test–a little more than a 10-horsepower total variance on a 450-horsepower engine. Likewise, oil pressure held steady throughout the test.

 

Motul engineers also monitor losses, as consumption is a great metric when assessing oils. Highly stressed oils can break down under thermal and mechanical stresses, allowing their compound chemical components to again become individual elements. 

Think about making butter: Putting heavy cream under physical stress separates the solids from the liquids. That’s a gross oversimplification, but it shows how easily chemical compounds can be affected by outside physical stresses.

When engine oil breaks down, some of those individual components are inherently volatile, allowing them to evaporate or even burn. If the formulation is robust enough, there will be little breakdown, which means little evaporation or burning, and therefore low oil consumption.

In the test Motul shared with us, total oil loss during the entire 24-hour test was less than a quarter of a liter–about 8 ounces, which is about a quarter of a quart. 

The test engine is configured so that oil samples can be periodically gathered for analysis throughout the test without stopping the experiment. 

As Wolff explains, this process indicates the overall health of both the engine and the oil circulating inside it. “The first thing we’ll look for is any metals being deposited into the oil,” he explains. “This gives us a pretty good idea of what could be wearing.” 

High iron readings, for example, can be a sign of premature crankshaft or cylinder liner wear. High amounts of aluminum could mean an issue with the cylinder heads. Copper usually points toward bearings, while other elements like lead and silicon can come from environmental sources like fuel or even sand ingested into the intake. The actual metals found, of course, will depend on the engine tested.

The techs also look at the oil’s viscosity throughout the test. “One of the ways we can look at the general effectiveness of the oil in an analysis is to look at the V100 number, which is a measure of viscosity,” Wolff explains. “All weights of oil have a window of viscosity they they’re supposed to hit at a given temperature. Oil that’s broken down will typically be outside that ideal viscosity range that it was when new. So, when we see a V100 number out of range, we know we need to start looking back at oil formulation and analyze closely.”

Then he adds a thought: “We don’t see that much, though.” 

Those analyses will also look at the softer elements that make up the oil itself: things like manganese, calcium, zinc, magnesium and phosphorous. 

These elements are often part of the oil’s additive package and help give a base oil stock its specific physical and chemical characteristics–like altering its surface tension, isolating unwanted combustion byproducts and more. Analysis during this dyno session can help the techs tweak and refine the additive packages to suit the constantly changing demands of race teams.

Racing Oil Is Special Oil

Many people imagine motor oil as this simple fluid that comes out of the ground and glugs into our engine. They think that pretty much all of it is the same with a few small variances. But the reality is that high-quality racing oils like Motul’s 300V lineup are a not simply products, but complex chemical systems designed to work under very specific sets of highly demanding circumstances. 

And while many street oils do an excellent job day to day for millions of drivers, ultimately they lack the single-minded focus of engineering needed to properly protect an engine that experiences nothing but extreme stresses. That’s where racing oils excel.

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