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Racing Oils – The Good, The Bad and The Slippery

I’ve been involved with formulating and testing racing oils for NASCAR and NHRA Pro Stock engines for decades. I’ve been very fortunate to have been able to combine both my career and my hobby at the same time.

By John Martin
As a motorhead physicist, I get to look at engine lubrication from the views of both an oil formulator and an engine failure analysis expert. Since I used nitromethane fuels when I raced funny cars, I’ve seen more than my share of engine failures. I’ve also formulated oils for use with alcohol and nitro burning engines, but let’s leave that discussion for another time.

Racing oils have evolved considerably over the past 20 years. In the ’70s and ’80s most racing oil formulations were merely designed on paper (arm chaired) because the racing oil market was considered to be too small to justify significant oil marketer R&D test expenditures. Most major oil marketers didn’t even offer racing oils for sale to the public. They offered race teams the same oils you and I were using on the street so they could advertise that fact.

By the 1990s several NASCAR teams had contacted their oil company sponsors/suppliers requesting racing oil chemistry which could help solve some engine durability problems. For example, I got heavily involved with a Chevrolet-powered race team to help solve a ring-welding issue. Early small block Chevy engines always placed exhaust valves adjacent to each other on the center cylinders. Pistons on these “hot spot” cylinders transferred metal to the top rings, interfering with good ring sealing.

Working for a specialty chemical company, where cost was virtually always an issue, I was amazed at how much money NASCAR engine R&D people were willing to spend to solve an engine durability problem (in order to finish first, you must first finish). The race team devoted considerable time and effort to developing a dynamometer test that duplicated the problem seen in the field. They then conducted 47 different dyno tests with test oils before solving that problem and a subsequent problem with piston pin bores. To an old “bucks down” drag racer this was like a kid being given the keys to the candy store.

Eventually the inevitable question came up. Can engine oil be used to produce more horsepower? It has long been known that lower viscosity (thinner) engine oils can produce more horsepower, because thinner oils reduce the power required to drive the oil pump. However, most racers utilized thicker engine oils, because they felt thinner oils sacrificed too much engine durability.

Testing showed that engines survived well on oils much less viscous than racers were currently using. And horsepower was increased on the order of 2-4%. Savvy engine builders who learned to reduce engine bottom-end clearances to maintain sufficient oil pressure learned they could run even thinner oils and gain still more horsepower. In the old NASCAR “qualifying engine” era, we developed some ultra thin oils, but those engines only had to live for a few laps.

Our extensive development work then focused on evaluating base stock and additive effects on both horsepower and durability. Synthetic base stocks have a slight edge over mineral oil base stocks, because they generally exhibit a lower coefficient of friction (think more slippery) than mineral oil stocks. But the word “synthetic” isn’t magic.Some synthetic base stocks aren’t measurably superior to mineral oils, and they are much more expensive. The key is to utilize dyno testing to maximize horsepower and race testing to guarantee adequate engine durability. It’s a delicate balancing act!

There are as many additive effects as there are additive combinations. Working for the world’s largest independent fuels and lubes additive manufacturer proved to be very advantageous in this regard. A dedicated R&D team was created to look at the horsepower potential of every additive in our repertoire, no matter how expensive. Typically, engine oils are formulated to very restrictive cost targets dictated by the oil marketer. As you know, race teams don’t concern themselves so much with cost; they need horsepower to enable victories.

Before discussing additive effects, I should briefly mention the major types of chemistry in typical automotive (let’s exclude Diesel for now) engine oils. Approximately 15% of automotive engine oils are chemical additives such as:

1. Antioxidants - The most cost-effective antioxidant is zinc dialkyl dithiophosphate (ZDDP), but many more, higher cost antioxidants also exist. ZDDP works by decomposing and creating a sacrificial film on the surface it is intending to protect.

2. Extreme Pressure (EP) Agents - Again ZDDP is the most cost-effective, but others exist. Most others are very expensive compared to ZDDP.

3. Detergents - Detergents are usually combinations of a rare earth metal and an oil soluble tail. Detergents are very basic and are used to control high-temperature deposits, oxidation, and oil acidity. Typically, the longer the oil change interval, the more detergent is required.

4. Dispersants - Dispersants control lower-temperature deposit formation (such as sludge) in engines.

5. Friction Modifiers - There are several chemicals which can be used to reduce engine internal friction. Typical passenger car engine oils contain small amounts to improve fuel economy, but since they are very expensive chemicals, passenger car oils don’t use a lot of friction modifiers.

6. Viscosity Improvers - All oils thin as they are heated. The amount an oil thins as it is heated is inversely expressed as its viscosity index (VI). The ideal oil wouldn’t thin at all as it is heated, so one should search for oils having the highest VI so they will thin the least as temperatures increase.

VI improvers have a down side, because most of them are not very thermally stable. Engine oils intended for use at extremely high temperatures should use as little VI improver as possible. Synthetic oils have an edge here since they naturally have much higher VIs than mineral oils.

Shear stability is also an issue with VI improvers. A balance must be maintained between shear stability and oil film thickness over the intended use of the race oil. A VI improver that shears too much can increase wear. A VI improver that shears too little can have more frictional drag thereby costing you horsepower.

So, what does this chemistry lesson have to do with racing oils? First, racing oils aren’t bound by the same requirements as passenger car or Diesel truck engine oils. For example, racing oils require less detergents and dispersants since the typical racing engine doesn’t go for thousands of miles before oil changes.

This is very fortunate since research and testing showed that both detergent and ZDDP additives work in the same manner. Both additives produce sacrificial films which adhere to the surfaces you’re trying to protect. Since detergents can actually compete with ZDDPs for the surface of the cam lobe, high detergent oils tend to give the ZDDP additive less surface on which to be effective. This is a major problem when using Diesel engine oils on high-lift, flat tappet cam lobes.

Secondly, racing oils don’t have to flow readily at lower temperatures since races are rarely run when it’s cold. Again, this is fortunate because many of the more effective, low-cost, low-temperature VI improvers aren’t very thermally stable. A good racing oil uses a more thermally stable VI improver and sacrifices some low-temperature flow.

Thirdly, racing oils don’t sell for $1.98 at your local Wally World. Cost restraints take a back seat to performance, so the oil formulator can utilize much more of those expensive anti-oxidants, EP agents, and friction modifiers than would be used in commercial passenger car and diesel oil formulations. How much difference can racing oils make? In the case of one NHRA Pro Stock team, a well-formulated racing oil produced 23 horsepower more than what they had been using. What would you pay to get 23 more horsepower?

So how can the Engine Builder reader use all of this lube oil knowledge to purchase the best racing oil for his application? First, never question the sponsor. If he gives you free oil and a bunch of money, then he must be right! However, two of the race teams we worked with told their oil company suppliers, “We will allow you to sponsor our car, but we reserve the right to run whichever oil our R&D says produces the most power.”

Secondly, don’t try to produce your own racing oil. ZDDP supplements have existed for decades, but most people don’t know the secret of blending ZDDP into oil. If the oil is cold when the ZDDP is added, the ZDDP won’t go into solution. If the oil is too hot, the ZDDP will decompose before it ever gets to the parts you were trying to protect. And “No,” I’m not going to tell you what the blending temperature should be.

Don’t fall for the racing oil which was created by adding ZDDP to existing engine oil (remember – too much detergent!). Look for the racing oil that was developed as a complete product using horsepower and durability test data, not marketing slogans. Marketing slogans might get you a free lunch, but they don’t guarantee more horsepower. Only good R&D does.

Beware of the person who comes to the game offering a “pinch of this and a dollop of that.” Racing oils aren’t designed that way. Let me give you an example. I’m one of the inventors of a well-known “Hot Rod Oil.” It contains a proprietary additive to prevent rust formation when engines are stored over long periods of time. No other additive company has this additive.

You just can’t develop oils quickly if you are trying to do it from a technically correct point of view. Try to locate the people who did the original design and test work. Look for the oil marketer who has spent years developing his product line and refining it. And remember no one understands oil chemistry as well as an oil chemist.

I also need to help you decide which viscosity grade to utilize in your engine. First, every rod and main bearing journal is a little oil pump. You would be surprised at how little oil pressure you need if you are certain you are getting adequate oil flow to all of the bottom end bearings. An engine’s oil pressure is determined by the total oil pressure at the oil pump outlet minus all of the internal leaks in the engine. The faster your engine spins and the less your rod side clearance (cheek clearance), the less oil viscosity you need.

However, don’t jump off the bridge. Try an oil one or two viscosity grades lower than what you are currently using ( for example try a 10W-30 instead of a 15W-50 ). Upon engine teardown take a look at critical lubrication points (cam lobes, pushrod tips, etc.) to make sure you don’t have any issues. If you are satisfied, try dropping viscosity again. If you have a short stroke, high revving normally aspirated engine, you might be surprised at how low you can go in viscosity before suffering durability problems.

Conversely, longer stroke, higher brake mean effective power (BMEP) engines need thicker oil film strength to prevent metal to metal contact. For example, blown motors require extra protection, particularly those with roots or screw blowers since they provide so much power at lower engine rpms.

Most operators of blown engines are more concerned with keeping parts off the pavement than with making more horsepower.

I was also asked to comment on break-in oils. Mineral oil based break-in oils have two major advantages over full synthetic racing oils. First, they are much less expensive. Those of us who like to break-in an engine rather quickly and then remove the oil change filled with metal particles and other debris (both visible and invisible) can do it more cheaply. Secondly, as I said before, full synthetic oils tend to be “more slippery” than mineral oils. I’m certain your engine will break-in on either oil, but it should do it more quickly with mineral oils.

If you’re concerned about engine durability with break-in oils, don’t be. I’ve personally observed two blown alcohol engines dyno at 2,500 horsepower each on an SAE 15W-50 break-in oil. Both engines then ran several hours of racing on a synthetic racing oil without any durability issues.

John Martin is a “motorhead” physicist who worked for Lubrizol for 25 years, and before that he worked for Shell. He has formulated and tested racing oils for NASCAR and NHRA Pro Stock engines for decades. He has 22 patents to his credit through his work on engine and driveline testing and optimization. He is currently building a fuel-injected 692 BBC for his street rod.