Slick Talk - Oil Tech

We tend to take oil for granted, but as engine output continues to climb, the oil's job will get more difficult. We tested this Quaker State 5W20 against a more viscous 20W50 and saw a minor improvement in power.

The line in Hollywood is that you can't be too thin or too rich. When it comes to high-performance engines, it's better to be a little rich than too lean, but with engine oil, thinner is definitely better. The OEMs are constantly pushing the envelope when it comes to all things that affect efficiency. One of the latest trends is to use thinner viscosity oils in search of more power and better fuel mileage as long as the oil doesn't hurt durability.

Car crafters are always looking for that next performance advantage, especially if it doesn't cost much and all you have to do is open a bottle and pour it in. We decided to take a closer look at thinner viscosity oils and do some testing to see if we could find a little horsepower from a pour spout.

To begin with, we spoke to Quaker State engineer Mark Farner about what goes into this new generation of synthetic engine oils and what kind of advantages they promise. Synthetic engine oil has always enjoyed a reputation both for its high-pressure lubrication performance and also its ability to withstand much higher engine oil temperatures than conventional petroleum-based oil. Conventional oils will tolerate engine oil sump temperatures of up to 250 to as much as 275 degrees F without difficulty. According to Farner, oils like Quaker State's full synthetics can easily withstand sump temperatures in excess of 300 degrees F, and he says that some oval track race teams are experimenting with temperatures as high as 350 degrees F.

Just because you may never put 3,000 miles on your garage queen engine doesn't mean that you shouldn't change the oil. Water can combine with sulfur and fuel contaminants to create acids that can eat bearings. The pits in these bearings were created by acids.

For a typical wet-sump engine, 300 degrees F is still extremely hot, but Farner says that synthetics, because of their molecular makeup, are better suited to withstand these temperatures. The downside is that additive packages do tend to break down faster in high-temperature environments, so if you plan on running oil temperatures in excess of 300 degrees, this would mean changing the oil after every track event regardless of the mileage.

For street engines that do not suffer this kind of track-day abuse, merely pouring in a synthetic does not mean that you can radically extend service drain intervals. Petroleum-based oils do not lose their base lubrication characteristics, what does suffer with use are the additive packages added to the oil. Synthetics are no different. Engines that see only limited use and ones that may never get up to full operating temperature can suffer from high levels of contamination that will require shorter drain intervals. For example, Farner says that for every pound of fuel burned in an engine, the combustion process also creates a pound of water. Some of this water will eventually end up in the oil pan. If the engine rarely sees sump temperatures that exceed 212 degrees F (water's boiling point), the water quickly mixes with another combustion byproduct--sulfur--to create acids that can eventually eat bearings if the oil is not drained.

Another reason to perhaps shorten drain intervals for performance engines is that oil is an important component of ring seal. If engine oil is contaminated with water, the water evaporates almost immediately around the rings, reducing ring seal and horsepower. Several years ago, we witnessed this firsthand at the U.S. Nationals when John Lingenfelter's small-block-Chevy-powered Pro Stock truck suffered an internal water leak. Once the water mixed with the engine oil, the 9,000-rpm engine lost double-digit power, which cost him the race.

The ultimate seal with piston rings is assisted with engine oil. The highest friction loss in an engine is found between the rings and the cylinder wall. Quaker State's research indicates that a too-thin oil can actually vaporize at the top ring, sacrificing ring seal.

Fuel is another contaminant that is often found in engine oil. Fuel can enter the oil from several places, most commonly as blowby past the rings. Even though we think of fuel as easily evaporated, according to Farner only the light ends of fuel evaporate at room temperatures. The heavier ends require temperatures as high as 450 degrees F to fully evaporate, which means that even at 300-degree oil temperatures, there can still be residual fuel that tends to reduce your oil's effective performance.

All of these are excellent reasons normal drain intervals are a good idea, even if you decide to step up to the more expensive synthetic oils. There are also synthetic blends offered by most major oil companies that are a composite mix of both synthetic and petroleum-based oils and are less expensive, but also reduce the oil's overall potential performance.