Every racer on the planet is looking for a magic bullet, that part or setup he or she thinks will bring a real edge over the competition. Racers look to any area on the car that may yield a performance advantage, and engine oil is not immune from this search for speed.
But, really, is there speed in engine oil? Can you gain power just by changing oil type and brand?
In reality, it is more about control of the oil in the engine rather than the oil alone being responsible for significant gains in power. The oil we have access to today is very technologically advanced, especially when you consider where it comes from and what it was prior to being poured into your engine.
In all honesty, when was the last time you or anyone you know suffered engine failure due to an oil-related breakdown? In this day and age, an oil failure and resulting mechanical failure is a rare occurrence. The most common cause of engine failure is a broken part, and that is usually a result of excess rpm, or taking a part or a combination of parts past their individual duty cycle lifetime. The more common vernacular is "worn out."
The fundamental question still remains: Can a change of oil type make more power? The simple answer is yes. But that is a cautious yes. Prior to rambling about looking for some elusive gains, let's define some parameters:
* We need to define the job the oil in your engine is doing.
* We need to define oil-related failure.
* We should engage in a small discussion on viscosity.
* How much of a power gain can we expect by changing oil?
This drawing illustrates the...
This drawing illustrates the relationship of the oil film to the bearing journal and the bearing. The film of oil can range from 0.001 to 0.0 during operation, depending on the load, the VI rating of the oil, and the clearance of the bearing (the greater the clearance in the bearing, the greater the opportunity to lose the wedge and have metal-to-metal contact). This can be due to oil leakage past the bearing and the oil pump's ability to distribute oil to the bearing.
The job that the oil does in your engine involves more than merely providing lubrication for the rotating and sliding surfaces; it also acts as a coolant. The oil removes heat from parts that receive no other cooling. The coolant in the cooling system removes heat from your engine in a gross perspective. The block and the heads get the coolant from the cooling system, and the heat from combustion and friction is conducted into the block and heads. It then goes into the coolant, and the heat in the coolant is rejected by the radiator. All moving parts are cooled due to the oil providing a path for the heat to travel from the bearing surfaces. That thin layer of oil that covers the moving parts in the engine transfers the heat created by friction through the oil and into the block and the heads. Oil also addresses the transfer of contaminants in the engine. It moves dirt and contaminants created by combustion from the internals of the engine into the filter, where they are removed from the oil.
We know that as the oil is routed to the bearings from the pump, it forms a protective layer of lubrication between the bearings and the rods, and the mains and the cam, and this layer is called a hydrodynamic wedge. This wedge prevents metal-to-metal contact between the bearing and the journals. This layer of oil also forms a path to carry away heat, a byproduct of friction. In addition, the oil needs to prevent foaming and act as a corrosion inhibitor to prevent rust.
An Oil-Related Failure
While this sounds like a simple problem, the reality is that oil failures are difficult to diagnose. When engines break at speed, the results are usually spectacular, and it is often difficult to pinpoint the exact cause. If your engine suffers oil pump failure or pump drive failure, the oil pressure drops to zero and failure is next. This is not a real oil issue; it is a lack-of-oil problem.
An oil failure occurs when the constituents of the oil start to break down and the oil loses its ability to lubricate. This can happen if the oil temperature rises to the level at which the oil starts to burn, or more specifically, starts to "coke." This phenomenon starts at or near 300 to 325 degrees F, depending on the type and brand of oil. While this is still classified as an oil failure, technically it is not. Something caused the oil temp to soar, probably some type of mechanical failure, and that caused the oil "failure."
In the real world, most weekly racers do not let the oil stay in their engines long enough for it to break down. They change the oil on a very regular basis (possibly too frequently), and even if they let it go a race or two the actual time accumulated is very small. The chances of the oil failing in your Saturday night racer are small, but this is not to say that you will have zero problems.
Viscosity is a measure of a fluid. In this case, it refers to oil's resistance to flow. There are other considerations as well: temperature, sheer strength, and/or resistance to sheer. A good example is that water is a low-viscosity fluid, and 30W oil has a much higher viscosity. The number on the oil bottle is the VI rating, or viscosity index, and 30W is the viscosity index number.
The next logical step is to understand that it takes more power to move higher-viscosity oils through your engine. If you fill an empty plastic bottle with water, you'll notice it doesn't take much effort to squeeze out the contents. But if you fill the same bottle with honey, a much greater effort is required to empty the bottle. The difference in the viscosity between the two fluids is why the effort increases. In the same way, your engine requires greater levels of power to move oil with a higher viscosity through the engine.