Understanding Oil 101
One of the most misunderstood yet critical parts of your engine is lubrication. This often confusing and misleading method of taking care of your rotary engine is a critical choice and one that could mean the difference between 100,000 and 200,000 miles of engine life. So, this guide will help explain the basics of oil and allow you to make more informed decisions when it comes to buying oil.
Before beginning this guide, ask yourself a few of these questions:
Would you buy a $2,000 set of racing tires to drive your vehicle to work or the grocery store?
Would you drive a fully built race car on the race track with nothing more than shorts, a tshirt and sandals?
Hopefully your answer is no to both questions. Why spend massive amounts of cash for tires that will never even see their full potential on the street? Why risk injury or death driving a race car without any proper safety equipment?
Every aspect of automotive modification has a specific application. Certain parts are best used in certain situations. Your choice of oil should be no different. This doesn't mean you should have 4 or 5 different motor oils sitting on your shelf. It simply means that before you can make good choices about lubricants you use in your vehicle you have to understand the circumstances which you use your vehicle. Street vehicles will have totally different requirements than race vehicles will. Once you have an understanding of lubricants you'll be able to understand how your car fits into the equation.
Section 1: What is oil's purpose?
Oil has two very important roles within your engine. The first is lubrication and the second is heat removal. Within the RENESIS Rotary Engine both of these elements are important and neither should be overlooked.
Oil's primary function of lubrication is one that is influenced by several factors. The oil's viscosity, type, temperature and usage life all determine h0w well oil can lubricate the surfaces of bearings and prevent metal to metal contact. The one thing to keep in mind is that everything with oil design is a compromise. There is no single oil that can do everything well. Also the application of oils for street cars and race cars are totally different. What might work well in a street driven motor may not work well in a race engine and vice versa. Do not base your oil decision on what works well in a race car or a track car.
Within the RENESIS oil has two different operating areas. First, oil is ran by a pump similar to a piston motor where bearings, and the inside of the rotor faces are lubricated. Oil provides a fair amount of heat dissipation in this area. The second area is within the combustion chamber itself. There, oil is injected via the OMP (Oil Meter Pump) and lubricates the rotary chamber and seals. While oil does provide some heat dissipation, the oil is consumed in the combustion process.
When it comes to choosing an engine oil, how you use your vehicle (application) is the most important factor. This is due to oil design being a compromise. Since one oil cannot do everything well it's important to choose an oil which functions the best within your conditions. For instance, you might want an oil that remains on your engine parts even after your engine has cooled down and be there when you start the engine back up. One such lubricant would be something like axle grease but you would have serious performance losses.
With a street driven motor, you are looking for an oil that has appropriate film strength, has flow characterists as close to water as you can get and will maintain it's viscosity and integrity at high temperature.
What are synthetic lubricants?
A synthetic lubricant is a oil that is designed from the ground up for specific characteristics by materials with predictable properties. Furthermore, the oil base stock can be supplemented with additives to improve specific characteristics targeted by the manufacturer. Most synthetic lubricants are derived wholly or mostly from petrochemicals while others are derived from coal and oil shale, or are lipochemicals which are from animal or vegetable oil.
So how are synthetic lubricants superior to mineral lubricants? Many synthetic oils exhibit a higher viscosity index, better thermal stability, better oxidation stability, and low volatility which reduces oil consumption. Synthetic oils are also capable of longer service life and in some cases better biodegradability. Some specific synthetic lubricants offer superior properties compared to mineral oil. Phosphate esters, for instance, are fire resistant, diesters have great ocidation stability and lubricity, and silicones offer exceptional viscosity indexes (VI). Polyalphaolefins are very versatile lubricants with low pour points, excellent thermal stability and they have good compatibility with petroleum lubricants and most seals that are used with petroleum lubes.
How do I read Viscosity Rates?
When it comes to oil advertising the numbers and meanings are very confusing and often misleading. So, what does all those viscosity numbers actually mean? When you see a 5w-20 viscosity rating that is actually called "Saybolt Seconds" and are measured using a Viscometer.
Viscosity is measured in centistokes (cSt) or kinematic viscosity.
The way these oils are tested is they are heated to a specific temperature and then that oil flows through a testing hole. The amount of time it takes the oil to flow through this area is how it's viscosity is detected. The higher the viscosity the larger the number. There are two numbers in this rating system for multi-viscosity oils.
Looking at a 5w-20 rating, there are two parts. The "5w" which is the oil's supposed viscosity at 40 degrees centigrade. The second is "20" which is the oils viscosity at 100 degrees centigrade. There are two misleading aspects when it comes to comparing oils.
First, looking at a 5w-30 and a 10w-30 oil. People think that both oils have the same viscosity when they are cold. This is not true. Second, looking at a 5w-30 and a 0w-30 people think that the 0w-30 is thinner than the 5w-30 at 100 degrees centigrade. This is not true either. A 5w-30 and 10w-30 have the same operational temperature viscosity (100 degrees) but different cold temperature viscosity. A 5w-30 and 0w-30 have the same operational temperature viscosity but different cold temperature viscosity. While these numbers can be confusing you can see how misleading the numbers are. So how do you unravel all the mess?
The key is to change how you think about motor oil. Don't think of viscosity as getting thinner as oil heats up but think about oil as getting thicker as it cools.
SAE Viscosity Chart