Performance engines built for racing deserve the best possible lubrication. Ordinary street oils don’t cut it on a race track.
By Larry Carley
The latest API-certified SN and ILSAC GF-5 motor oils are fine for everyday driving in late model vehicles, but most off-the-shelf motor oils (even many synthetics) come up short in the anti-wear department in a racing application – especially if the engine is running a flat-tappet cam or a radical roller cam with a lot of valve spring pressure.
Specially formulated racing oils are available from a variety of companies. The base-oils and additives that are used in these products is a proprietary secret, just like the Colonel Sander’s recipe for fried chicken. Nobody is going to divulge the exact ingredients and their percentages that make their product what it is, though most will tell you something about the basic oils and additives they use and how great they perform (there’s a lot of hype to sift through from the marketing department!).
Most brands offer a range of viscosities from which to choose as well as various additive packages for everything from drag racing to circle track, for gasoline or alcohol fueled engines, and even air-cooled motorcycle engines.
Many suppliers of racing oils refine their own oil and make a full line of lubrication products for both street and racing. Other companies buy their base-oils from other refiners and have their products blended to their own specifications. Either way, the end product is a high-quality lubricant that is designed for the rigors of professional racing.
What makes racing oil different from off-the-shelf conventional and synthetic oils that are marketed for everyday use? Basically, racing oils are formulated for racing and nothing else. They are designed to handle higher temperatures and higher loads. Most racing oils are NOT designed for everyday street use, although there are some special street performance oils that offer increased wear resistance and thermal protection for higher-output engines.
Motor oils contain zinc and phosphorus as high-pressure anti-wear additives. But in recent years, the amount of ZDDP (zinc dialkyl dithiophosphate) that is allowed in street oils has been reduced to prolong the life of the catalytic converter and oxygen sensors (both of these metals are contaminants that can reduce the life of the catalyst and sensors). Motor oils contained 1,500 parts per million (ppm) of ZDDP back in the 1980s.
In the 1990s, that was reduced to 1,200 ppm, and in 2005 it was cut again to 600 to 800 ppm. The rationale was that modern engines with roller cams or OHC cam followers don’t require as much ZDDP anti-wear additive as older engines with flat-tappet cams. The reduced levels of ZDDP were also deemed adequate for most passenger car flat-tappet cam engines. But as many racers learned the hard way, today’s street oils with reduced ZDDP are wiping out cams in performance engines with flat-tappet cams, radical roller cams and engines that are using lots of valve spring pressure.
The solution? Some racers switched to diesel motor oils because they still contained higher levels of ZDDP. But that also changed a few years ago when the amount of ZDDP in diesel oils was reduced to 1,200 ppm. Most experts feel that 1,500 ppm of ZDDP (or more) is required to protect cam lobes, flat-tappet lifters and the needle bearings in roller lifters. Anything less than that is asking for trouble. Some racing oils also contain molybdenum in various forms as part of their anti-wear package.
ZDDP crankcase additives are available that can provide the required anti-wear protection for older engines and performance engines that are running street oils. These additives are designed to supplement street oils, not racing oils, so follow the directions and precautions on the product.
Some oil engineers caution against using additives with racing oils. A motor oil performs best with the additive package that is blended into it. Adding supplements may create an overdose of some ingredients and upset the balance of other ingredients. Too much zinc can interfere with other additives (such as detergents), and increasing zinc levels beyond the recommended 1,500 to 2,500 ppm concentration will not provide higher levels of scuff and wear protection. For this reason, the experts recommend using a racing oil that is formulated from the get-go to provide the required anti-wear protection needed for a performance engine and to NOT add anything else to it.
Thermal stability, which is the oil’s ability to resist oxidation (burning) when it gets hot, can also be an issue when ordinary motor oils are subjected to the rigors of racing. Synthetics are much better in this respect because they can handle higher temperatures without breaking down. But the base oil and additive package in a motor oil formulated for everyday driving (including synthetics) is not going to provide the same level of performance as the higher quality base-oils and additives that go into specially formulated racing oil. Consequently, an off-the-shelf street oil is not going to perform at the same level as a racing oil.
Base Oil Chemistry
Base-oils are categorized according to their performance characteristics. Viscosity Index (VI) is one measure of oil quality. Anything over 100 is good, with higher numbers being best. Group I base-oils are the lowest category. They are the least expensive oils to refine and typically have a VI rating in the 80 to 100 range. Most conventional street oils today use a Group II base oil (usually a VI of 100 or higher) plus a small percentage of Group III (VI over 120) synthetic oil to meet API SN or ILSAC GF-5
Racing oils start with higher grade base-oils (Group III, Group IV synthetics and even some Group V oils) to get a higher level of performance. Group IV oils are full-synthetics and include POA (polyalphaolefin) which is the most versatile synthetic. POA does not contain any sulfur, phosphorus, wax or metals. It can withstand elevated temperatures, and has a VI rating of 135 to as high as 300. That’s why POA is used as the base oil in many racing formulas.
Oil Viscosity and Heat
Heat is a real challenge in performance engines because the engine may be making anywhere from one and a half to three times as much horsepower than a comparable stock motor, depending on what’s been done to it. That’s a lot of waste-heat going into the block and other engine parts.
Direct oil flow to the crankshaft helps cool the main and rod bearings, and splash lubrication helps lubricate and cool the pistons and wrist pins. Add some pin oilers to direct oil at the pistons, and the oil takes on even more cooling responsibility. Oil also helps cool the upper valve train, including the rockers and valve springs. Consequently, the oil picks up a lot of heat.
The type of oiling system on the motor can help manage much of this heat by routing the oil into a reservoir tank and through an external oil cooler. But engines that are running an internal wet sump oiling system with no external cooler can heat up the oil very quickly in a racing environment.
Racing oils are formulated to handle temperatures that cause ordinary street oils to break down. This requires high-quality base-oils and additional friction-modifiers. Many racing oils are designed to handle temperatures in the 250° to 300° F (or higher) range.
The oil in a crankcase of a daily-driver is probably going to stay in the 165° to 185° range with normal driving. It can climb higher during hot weather, with sustained high-speed driving, when towing a trailer or when driving aggressively. But it is not going to reach the kind of temperatures a race engine can experience.
The least demanding racing application as far as oil temperatures are concerned is drag racing. The engine is started cold with little or no warm up time, then it’s a short burnout and a quick blast down the quarter-mile before going back to the pits. The oil never gets very hot, so a relatively thin, low viscosity racing oil such as 5W-20 and 5W-30 may be used without fear of overheating the oil.
Thin oils can also be used in certain asphalt circle track engines, too, provided the engine has an adequate oil-reservoir, good oil-cooler and radiator to help manage the heat. Thin oils are typically used with tighter bearing clearances and reduced oil pressure (which saves horsepower).
By comparison, more traditional racing oil viscosities such as 15W-40, 15W-50 and 20W-50 are thicker and better able to maintain their viscosity at elevated temperatures in endurance applications such as circle track and road racing. The heavier oils work best with increased bearing tolerances and perform best when preheated before a race.
Lower viscosity multi-weight oils are used in late-model passenger cars for a variety of reasons. Thinner oils reduce friction and save fuel, but they also flow better when cold and speed lubrication to critical upper valve train components such as overhead cams in late-model engines. That’s why most new cars today come factory filled with 5W-20, and some even 0W-20 motor oil.
Thinner viscosity racing oils can also reduce friction to yield power gains depending on the base-oils and additives used. You’re not going to see huge power gains, but with some oils it is possible to see another 1 to 3 percent more horsepower at the flywheel. On an 800 hp engine, that could be another 8 to 24 more hp on the dyno.
Street oils are formulated for longer service intervals (up to 7,500 miles or more), so they require more detergents and dispersants. Racing oils don’t have to go those kind of distances so the additive package can be very different. A racing oil still needs good detergency to handle fuel dilution of the oil in the crankcase, but not as much detergent or dispersant as a typical street oil. So racing oils need to be changed fairly frequently. One expert said if you can smell fuel in the oil or see that it is turning dark, it’s time to change it.
Choosing a particular brand and viscosity of racing oil depends on a lot of variables: how tight you’re building the engine, how much heat the oil will have to endure in a racing application, the kind of oiling system on the motor, the kind of fuel the engine will be running, how much “extra” horsepower you are trying to gain by using a thinner/slipperier oil, how much anti-wear protection the engine will require (depending on the type of cam, lifters and valve springs), your past experience with a particular oil, if your customer has a brand preference or sponsorship to consider, and the advice of the oil supplier.
Nobody knows their products better than the ones who make them, so don’t be afraid to ask an oil supplier what type of racing oil they recommend for the engine you are building.
If you’ve had good experience with a particular brand of racing oil and are comfortable with how the oil performs, there’s probably little or no incentive to try something different. After all, if it isn’t broke there’s no need to fix it. Trying a different brand or viscosity of oil is always a gamble. A different oil may run cooler, protect better and/or give you some extra power – or it may not. The only way to find out is to find out what kind of oil some of your competitors are using and try some yourself.
Some oil companies publish guides listing the type of oil and viscosity they recommend for certain types of racing. If you’re building a blown nitro engine for a Top Fuel dragster or Funny Car, you’ll need a heavy oil like 70 weight. In that kind of application, the oil isn’t going to last very long. Most Top Fuel racers dump the oil after every run. The real penny pinchers may let the old oil sit in a bucket for several days for the nitro to separate, then drain off the oil and reuse it another couple of times before discarding it completely.
The point here is that oil is cheap and engines are not. You have to use the right oil and change it as often as needed to keep the engine alive.
For enduro road racing or circle track, a 20W-50 or even a straight 40 or 50 weight oil may be the best choice. For an alcohol fueled engine, an oil with a special additive package designed for alcohol would be
If you’re building a 500 to 800 horsepower big block Chevy for a customer who wants to drop the engine in a hot rod or street rod (which will probably only be driven during warm weather), a 20W-50, or straight 40 or 50 weight oil would be recommended to handle the heat.
On the other hand, if you are building a late model Chevy LS motor for a road racer the street/strip, a lighter multi-viscosity 5W-20, 5W-30, 10W-30 or 15W-40 might be the best choice depending on how much power the engine makes and how hot the oil will get.
If a racer doesn’t know what kind of oil temperatures are normal for his kind of racing, he should invest in an oil temperature gauge or oil temperature sensor so oil temperatures can be monitored. Once this vital piece of information is known, it’s easier to pick an oil based on how much heat the oil will have to withstand.
Equally important to choosing a good racing oil for a performance engine is using the correct type of break-in oil when that engine is first fired up. Conventional 30 weight oil is usually recommended for lubricating internal engine parts as the engine is being assembled, with moly assembly lube being applied to the cam lobes, the bottoms of flat-tappet lifters (or the needle bearings in roller lifters), rocker arms and the tips of pushrods.
Once the engine is together, the crankcase should be filled with a mineral-based (not synthetic) non-detergent oil. The trouble is, non-detergent oils are hard to find so many oil companies now formulate their own special break-in oils. These products typically contain no detergent and have extra ZDDP and other anti-wear additives to help protect the cam and lifters during break-in. Break-in oil viscosities may range from 0W-10 (for engines that will be running a really thin oil) to 5W-30 to 15W-40.
The most critical step in the break-in process is getting the piston rings to seat. If the rings don’t seat, the engine will use oil and never develop good compression. Plateau honing the cylinders before it is assembled goes a long way towards assuring a good ring seal. But even with a good plateau hone, it still takes a little run-time to fully seat the rings. We’re talking 30 to 45 minutes of run-time at varying engine speeds and loads to seat the rings, and maybe up to an hour or two of run-time as needed, but no more.
Once the rings have seated, its time to turn it off and dump the break-in oil. Once the break-in oil has accomplished its mission, it’s history. You can recycle it, burn it in a waste oil heater, or even use it in an older diesel engine or farm tractor. But don’t leave it in any longer than necessary. A common mistake is to leave the break-in oil in the engine while you’re tuning it on a dyno. Break-in oil is not racing oil, and if you push it too hard and get it too hot, it’s going to burn and possibly wreck the new engine you just put together.
Make sure you change the filter, too, because any residual honing abrasives and wear particles that are floating around inside the engine can cause a lot of problems later if not removed.
For Oil Supplier contact information, visit enginebuildermag.com and use our interactive Buyers Guides.
Engine Builder Staff
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