What level of power can be gained through a change of oil? The answer to this question is dependent on how the current oil is working. If you are using oil with a very high viscosity, your oil pump will be working harder to pump this oil around your engine. Does the oil you are using have a viscosity number that is too high? Can your engine be run safely with oil that has a lower VI number? (This is a big question.) If your engine is older and the internal clearances have grown due to engine wear, you may be taking a real risk using oil with a lower VI number. Remember that the sheer strength may be sacrificed with a lower VI rating and it may be possible to squeeze the oil out of important areas such as the main and rod bearings. This can lead to metal-to-metal contact if the oil gets squeezed out, leading to excessive friction and damage.
In a perfect world, you would run the thinnest possible oil, one with the lowest VI rating that will still maintain the hydrodynamic wedge to keep the moving parts from touching. This is the point at which the racer has to make some compromises with power versus durability. Running oils with a very low VI number might make more power for a brief period of time. But the low VI numbers will mean that the ability of this thin oil to protect the moving parts of the engine will be less than oil with a higher VI number. This trade-off of power versus durability carries a significant amount of risk to your engine and your budget.
It is not uncommon for racers in the higher levels of the sport to change engine oil to gain power for a brief period of time. For example, some NASCAR teams may run oil with a very low VI number to gain an edge during qualifying. This is for a very limited time, and quite frankly, these guys are balancing the cost of an engine against the cost of not making the show. Once qualifying is over, the heavier oils go back into the engine. How low can they go? From a commercial perspective, you can get some brands of oil in the 5-to-10-VI range, and if you have special contacts in the oil industry, VI numbers of less than 5 can be obtained. But the cost is just not worth it for the weekly racer.
What kind of gains can be had by using these ultra-thin oils? Many engine builders say that gains from 1 to 3 percent are attainable. What does that mean for the NASCAR Nextel Cup guys? The claimed power output from a Cup engine is in the 750-800hp range, so they could expect a gain that runs from 7.5 hp to 24 hp. While the numbers sound good, the expectation for the weekly racer should be nowhere near that level of gain. If the local racer is getting 300 to 400 hp, they might expect a gain from 3 hp to 12 hp. This level of power increase is just not worth it for the racer on a budget. Not to mention that these very-low-VI-rated oils are expensive. And you need to consider the state of tune your engine is currently in compared to the engines found at the highest levels. A transporter back in the pits probably has at least three new engines just waiting to go in should the one used for qualifying expire. That is a risk NASCAR racers are willing to take.
If your engine is in less than optimal condition-say, for instance, you are running a Bomber class and the engine you are currently racing with was rescued from duty as a grocery hauler-then changing the type of oil may not yield any discernable differences in power.
It is clear that there is power in the oil, and that power comes at a price. Special lightweight oils have a premium price at the point of purchase. And we need to remember that some racing oils are formulated with less or no detergent additives because they are designed to be changed more frequently.
It is also clear that there are some power advantages with oils that have a lower VI rating, but this power comes at a price-potential accelerated engine wear and potential engine damage. This is not to say that the low-VI-rated oils will hurt your engine, but if you are planning on running low-VI-rated oils, the engine needs to be built with the idea that low-VI oils will be used.
From a racer's perspective, oil is separated into two types: mineral (or petroleum) and synthetic. Oils used in the automotive industry are petroleum derivatives, as even synthetic oils are made from petroleum-based stocks.
Where the oil comes from makes a difference as to how it will be required to be refined. Some oils have a higher sulfur content, while others may be less pure, and this will determine how the oil will be refined. Some of the more sought-after oils are the sweet crude, like those found in Pennsylvania. These base stocks are considered by some to be superior, from a chemical makeup. Brad Penn racing oils are made from this Pennsylvania crude oil. The Pennsylvania crude has some unique chemistry that makes this type of oil very suitable for use in racing engines.
Brad Penn racing oils also have added zinc for additional load-carrying capabilities. The refining process used gives this oil some characteristics that are advantageous to the racer. The oil has an affinity to metal, insomuch as it sticks to metal. This can be a good thing, especially when you are running the very high loads that are now so typical.
Oils from Mobil One and Amsoil are examples of the synthetic group of oils. The term "synthetic" refers to the fact that these oils are made up of chemical compounds that were not part of the crude oil as it was pumped out of the ground.
A term that you will hear associated with synthetic oils is "man-made." This is partially true. As previously mentioned, they are still made from oil stocks, with other chemical compounds added to the oil during the refining process. Synthetics have some very real positives for the racer. Generally, these oils have improved lubrication properties, lower cold cranking requirements, and greater stability in the VI index over a greater range of temperatures and resistance to oxidation.
On the down side, synthetics cost more than straight petroleum oil, and some types of gaskets do not seal as well when used with synthetic oils. Many times, oil companies mix some synthetic oils with petroleum oils to make a hybrid oil. These oils offer many of the positives associated with the two types of oil at a much lower cost than straight synthetic oil.
The gain in performance for the Saturday night racer is negligible. You may be able to gain a greater level of performance by spending the same amount of money on new tires or shocks and leaning toward a greater level of dependability from your engine. The choice is yours.