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.