Motor Oil Myths

Of all the inventions man has created, few rival the Internal Combustion (IC) engine. This amazing machine does the work of many men by producing horsepower and torque, and does so in a short time and generally with great efficiency. In the last 100 years there have been many improvements in power, emissions, and reliability to the IC engine.

Racers and enthusiasts continually take these engines to the edge by extracting greater horsepower and torque as compared to stock units. We enhance output with aftermarket parts and trick tuning, but rarely do we pay much attention to such things as the oiling system--at least until the engine burns up.With that said, we urge you to get educated. Lubrication is necessary, and picking the right kind is important to longevity and performance. Thankfully, it really isn't that hard if you know the facts. Without them, though, even the most carefully prepared engines may lock up and die.

Engine Oil
We know that oil lubricates the engine, but it also cleans it and provides a means for cooling by dissipating heat. Oil also suspends minute particles of foreign matter so they don't become imbedded in critical components such as the bearings and/or the oil pump. In addition, oil must work in a harsh environment, getting whipped by the crank, dragged by piston rings, and forced through small clearances.

A quality product is important, but what's the difference between that dusty $1.29-per-quart oil found at the supermarket and the specially designed racing oils that sell for more than $10 per quart? And what's the difference between mineral oils, synthetic oils, and blended oils?

Frankly, there are enough grades and types of oil to make your head spin. Nevertheless, at the end of the day, most people just want to know what's the best oil for their application.

The lubricant we know as "engine oil" comes in many grades and blends. Regardless of the type, all oil begins life as crude oil. Crude oil can be many colors, but most of us know it as the thick, black stuff that comes from the ground.

Crude oil is a versatile product containing many hydrocarbons--molecules containing hydrogen and carbon. Hydrocarbons have the potential to release a lot of energy, but they must be refined before they can be used efficiently.Refining is a process that separates the chains of hydrocarbons within the oil. Once the oil is refined, many useful substances can be created, including gasoline, diesel fuel, kerosene, petroleum gas (used for heating and cooking), along with heavy oils and lubricating oil.

"Crude oil is refined to make base stocks," says Mark Ferner of Quaker State. "Base stock makes up about 80-85 percent of a quart of oil. The remaining percentage is made up of about a dozen additives that enhance certain properties. These may include anti-wear, detergent, dispersants (which hold debris in a suspended state), foam inhibitors, friction modifiers, and a few others."

Mineral-based oils are the most common, but there are also synthetics and blended oil containing a mineral/synthetic mix.

Synthetics are known as man-made oils, but they are not created totally from scratch. "Synthetic oils are created from crude, but the refining process is much different than with mineral-based oils," says Jared Martin of Royal Purple. Synthetics are first broken down or refined well beyond that of mineral oils, and then they are practically recon-structed so the chains or molecules are uniform. This additional refining also drives up the cost of synthetics.Synthetic oils offer superior high-temperature oxidation resistance, higher film strength, a stable viscosity base, and better low-temperature flow characteristics. This makes them a good choice, as long as you can afford the extra cost.

In addition to mineral oils and synthetics, there are also blended oils, which are made up of a combination of mineral and synthetics. Blends allow manufacturers to build customized oils to fit the cost, compromise, and performance that customers desire.

Lubrication
On the most basic front, the job of the engine oil is to lubricate moving parts inside the engine. Where there are moving parts, there will be friction, and friction takes power to overcome. Excess friction leads to metal-to-metal contact between internal moving engine parts. Without lubrication the parts would grind together and the engine would seize. On the other hand, reduced friction means more power and greater overall efficiency. It also reduces wear and increases engine life.

The oiling system is relied upon to get oil to the critical parts of the engine. Most oil systems are made up of an oil pan, an oil pump, a pump pickup, an oil filter, oil passages, and a return system. Oil is picked up and fed to the pump and then the filter. Oil is then routed to the passages in the block and to the clearance areas between the bearings and the crank. Oil then flows through passages in the crank, which feeds the rod bearings. Excess oil is thrown from the crank and it splashes on the cylinder walls to lubricate piston and ring assemblies.

Passages in the block also feed the cam and the lifters. The lifters feed the pushrods, which feed the top end of the engine. Through passages in the heads and block, oil drains back to the pan and the cycle starts over.

This type of system is called a wet-sump system. Dry-sump systems, used primarily in racing, use a remote reservoir and an externally mounted pump. The pump supplies oil to the engine through lines. This pump also scavenges the pan of any oil and feeds it back to the reservoir. Horsepower can generally be found with a dry-sump system because the crankshaft never contacts the pool of oil, and windage is greatly reduced.

Viscosity
One of the most commonly used terms found in conjunction with oil is viscosity. Viscosity is simply the oil's resistance to flow, but we commonly think of it as the oil's thickness.

"The Society of Automotive Engineers (SAE) sets the parameters for which lubricant viscosities are determined," says Martin. "Viscosity is defined as the resistance to flow at a given temperature. But, without a corresponding temperature, a viscosity measurement is meaningless. There are two ways of measuring viscosity: Saybolt Universal Seconds (SUS) and Centistokes (cSt). Each lubricant is measured at two temperatures to determine the SAE viscosity simulating ambient temperature flow and operating temperature flow. When measuring in centistokes, the lubricant's flow is measured at 40 C and 100 C. When measuring in SUS, the fluid is measured at 100 F and 212 F."

In lay terms, thin oil receives a low viscosity number, such as SAE20, and thicker oil receives a higher number, such as SAE40. It's important to remember that the SAE number is arbitrary because it labels the oil's viscosity at one given temperature, and that viscosity can change with temperature.

MultiGrades
Now that you understand viscosity, it will be easy to understand the difference between the grades or weights of oil. For the most part, there are two types: straight weight or multiweight (or multigrade).

Most street engines operate in a wide temperature range. Therefore, the oil must be able to adapt when it is extremely cold or brutally hot. For instance, the oil must flow sufficiently during cold-start conditions when the engine has been sitting overnight in freezing temperatures, yet it must not thin out too much once the engine reaches operating temperature.

Multigrade oils bridge this gap wonderfully because they have the ability to change viscosity with temperature. To understand, let's look at a typical multigrade oil, such as a 5W30.

So what do those numbers and letters mean? Simply stated, the "5" relates to the viscosity at ambient temperature (normally 100 F), the "W" stands for Winter, meaning the oil is suitable for winter use, and the 30 is the viscosity of the oil at the second test temperature (normally 212 F). In other words, when the engine is cold, the oil acts like a 5 weight and it flows easily. As the temperature gets to 212, the oil thickens and acts like a 30 weight.But there's a catch. For years we've been told that oil thins out when it gets hot. This theory tells us that the opposite is actually occurring. So which is right?

Here's the deal. Multigrade oils use polymers, which are added to a lightweight base stock. The polymers react and prevent the oil from thinning much once the oil temperature goes up, so the oil does not show a drop in viscosity. This is not the case with straight-weight oils.

It's important to remember that viscosity ratings are given at a certain temperature, and the oil changes viscosity as temperature changes. Therefore, you cannot directly compare straight-weight oil to a multigrade unless you know the exact operating temperature of the oil and its corresponding viscosity. Straight-weight oils become thinner as they are heated, so viscosity does indeed drop.

Oil Level

Some folks feel the safe bet is to overfill the oil pan. This, undoubtedly, is based on the "more is better" theory, but overfilling the oil pan is not a good idea. Raising the level in the pan beyond what the factory recommends will most likely cause the oil to surround the lower half of the crankshaft, causing excessive drag and windage as the crank rotates. Excess oil will also be splashed on the cylinder walls, increasing the chance that the oil will get past the rings where it will be burned in the combustion chambers. This alone can lead to detonation and smoking--it also kills power and economy. If you feel the need to run additional oil for added protection, install a larger-capacity pan or an Accusump system.

When it comes to road racing, go with the recommended level of oil in the pan. If you want more capacity, install a remote cooler along with the aforementioned oil accumulator/Accusump.

During extended severe or road-racing use, the engine and the oil will be taxed much harder than in drag racing or normal street driving. Having sufficient oil in the engine will do a number of things to improve performance. Know that the oil helps the engine dissipate heat, therefore sufficient oil supply will help keep engine temp down. Also, a low level increases the chance of starvation in cornering and braking. For this last reason, we highly recommend an aftermarket oil pan with proper baffling.

One trick used by drag racers (especially when the stock pan is used) is to reduce the oil level in the pan. Lowering the oil level keeps the oil off the crank, thereby reducing drag and releasing horsepower. Note: This is not recommended with modular engines because they require more oil at the top end of the engine to lube the camshafts. Lowering the oil level can starve the cams, leading to damage. In addition, the crank is mounted higher in the block when compared to Windsor engines, so there is less benefit from having less oil in the pan.

Filtration And Oil Change
Ever notice that while you pour in that clean, golden oil it never comes out that way? More often than not, it comes out black, and even its smell changes. Sometimes it will reek of fuel, other times it just smells nasty. Well, believe it or not, this is good. By the oil changing color, you know that it is doing its job of ridding the engine of contaminants, which can be anything from small particles of dirt to metal fragments picked up internally. The oil carries these particles until it is captured by the oil filter or drained from the engine.

Despite the best efforts in filtration, some of these particles will make their way into critical components. This leads to increased wear of the bearings and the cylinder walls. For this reason, you must pay close attention to your oil. Often, it tells a story. You can further inspect the oil by cutting open the filter and/or having a lab analyze the oil.

The oil will contain contaminants from combustion, which leaks past the rings. They can break down the oil and shorten its life, too. This is common in racing engines, due to richer mixtures.

For these reasons, we strongly suggest following the manufacturer's recommendations for changing the oil, or changing it more often if you are a hard driver. In racing, you should use your own discretion or that of your engine builder. Some racers hold out, but a few quarts of oil and a filter is cheap insurance. For that reason, I swap out the oil in my own race car every other weekend. That's usually about every 12-15 runs.

Lastly, there are a variety of oil filter types available. Most will be the spin-on type, although some use a reusable filter and can be disassembled, which allows you to inspect the filter. Routine inspections can reveal metal in the oil, and this helps to catch a problem before it ruins your engine.

Distilling The MythsQ: Can I break-in my engine using synthetic oil?
A: Yes and no. Most expert engine builders suggest breaking in a new engine using mineral-based 30W oil, however, this may not be necessary. "I've spoken to the formulators who make the synthetic oil and the response has been that, theoretically, synthetics have properties above and beyond conventional oils, and that makes them fine to break in an engine," says Mark Ferner of Quaker State. "I haven't had anyone show me a paper or a report that says you can't [break-in an engine with synthetics]. In fact, many manufacturers are using synthetics as the factory fill. But, still, 95 percent of race-engine builders recommend conventional oil for break-in. We say go with what has worked in the past.

Q: Can I switch back and forth between synthetic and mineral oils?
A: Yes. "In most cases you can switch back and forth, but I recommend that you stick with one brand or line of oil," says Ferner.

Q: Do synthetics cause leaks?
A: No. "When synthetics first came out, there were questions about the oil causing O-rings or gaskets to swell, resulting in leakage at these seal points. But this just wasn't the case," says Ferner.

Q: Can I go longer without changing the oil if I use synthetics?
A: Yes and no. Most of the experts we spoke with agreed that the type of oil (mineral or synthetic) doesn't matter as much as the type of driving and the condition of the engine. Cold-starts, racing, poor engine tune, severe street-duty, and dirty conditions contribute more to contamination and breakdown of the oil than does normal driving. Once the oil can no longer provide maximum protection, wear can take place. Therefore, it is important to follow the manufacturer's or your engine builder's recommended schedule for oil and filter change.

Q: Will synthetics increase the horsepower in my engine?
A: Yes and no. Some specially designed racing synthetics are more slippery than conventional oils due to the additives or lack thereof. However, it is normally the low viscosity that reduces friction and increases horsepower. Some specially formulated racing oils are super-thin and carry ratings of 0-7W, while some are even lighter than that. But be aware that the engine must be built with clearances designed for these thin oils.

Q: What is the lightest-grade oil I should use?
A: Most experts will tell you that thinner (lower-viscosity) oil reduces friction and improves power. While this is true, thinning the oil can lead to premature bearing failure and blow-by if the engine is not set up to run with thin oil. Race-engine builders often alter the size of the clearances for use with thin or thick oil (depending on the application). We recommend you consult your engine builder before dumping in super-thin oil. For most strip applications, you can go with a 5-20W, although some engines will make more power with 0-10W. Generally, boosted engines will require thicker oil.

Q: Can I lower the level of oil in the pan to increase power?
A: In a word, yes. However, altering the oil level can have both positive and/or negative effects on the engine. In most cases, lowering the oil level will increase power. This comes as a result of getting oil away from the spinning crankshaft, thus reducing parasitic drag. To see why, tie a weight to the end of a string and begin whipping it around. Now, place a 1-foot-deep pan of oil on the ground and let the weight go through the oil at the bottom of each revolution. As the rock hits the oil, it will be slowed and oil will splash all over the place. Lowering the oil level allows the weight to clear the oil, thus maintaining its speed. In addition, less oil is displaced and/or splashed, and drag is reduced. This equals horsepower. We've found that removing a quart of oil from a late-model 5.0 Mustang (with a stock pan) to be worth almost a tenth of ET. But we caution you--reducing the oil supply increases the chance of running the pickup dry and starving the engine for oil. Additionally, don't try this with your modular engine, as these engines require more top-end oiling, and damage may result.

Q: Can I add a quart of oil to increase engine life?
A: No. In contrast to draining oil, adding oil is not a good idea. Some racers believe they can overfill the pan by a quart to increase engine life, but nothing could be further from the truth. Overfilling the pan will cause excess drag on the crankshaft: This kills performance and decreases engine life. The only exception is with the use of an aftermarket oil pan, the majority of which have enlarged sumps that often allow for an increase in oil capacity. In those cases, extra oil will generally assist in increasing engine life.