Technical info engine oil
Taking the Mystery out of Engine Oil
The more we know about engine oils, the more wisely we can
choose the best oil for cars and trucks.
Engine oils do more than you think
It's easy to name the main function of engine oil: to lubricate every
moving part of your engine with a protective film that reduces friction.
But engine oil has at least four other duties, and failure to perform them all can seriously reduce the performance and life of your engine.
First, your engine oil cleans your engine. Gasoline and diesel engines can produce soot, ash, acids, and moisture which form sludge, varnish, and resins. If they collect on critical engine parts, it means serious trouble. A quality engine oil keeps them suspended until filtered out or drained away when you change your oil.
Next, oil seals microscopic hills and valleys on piston rings and cylinder walls. Without proper sealing action, you'll lose power and waste fuel.
Engine oil also protects your engine against rust and corrosion.
Finally, oil cools vital parts such as camshaft, rods, and pistons that the engine coolant in your radiator cannot reach. As much as 40% of the cooling job in your engine is performed by the oil in your crankcase.
How to read an engine oil label
Detailed information about the quality of your engine oil is contained in the APIusually found on high quality oils.
(for example, SAE 5W-30). Viscosity is a measure of the oil's flow characteristics at certain temperatures. The first number / letter combination (e.g. 5W) indicates how well the oil will flow to lubricate critical engine parts at low temperatures. The lower this number, the more easily the oil will help your engine to start in cold weather.
The second number (e.g. 30) indicates the oil's ability to lubricate the engine at high temperature. In this case, the higher the number the thicker the oil. A multi-grade oil, SAE 5W-30 in this example, satisfies the requirements of both cold start and high temperature viscosity grades.
 "SJ" identify the type of engine the oil is designed for and the performance rating of the oil. "S" ratings mean the oil is suitable for gasoline engines, and "C" ratings such as CH-4 designates oil for diesels. API Category SJ was introduced in 1996 and should be used for all current and earlier cars in North America.
"Energy Conserving", this label is used to identify oils which have been proven in laboratory tests to help reduce fuel consumption compared to standard reference conditions.
Cold facts about viscosity index
The Viscosity Index or VI measures the change of an oil's viscosity over a wide range of temperatures. The higher the VI of an oil, the less it will thicken when cold, and the less it will thin out when hot. A high VI oil will be more effective when lubricating your engine over a wide temperature range. Changes in viscosity and VI result in different viscosity grades, so you can pick the best grade for your vehicle. Here's a description of the five most common SAE multi-grade oils:
ow-30
5w-30
10w-30
10w-40
20w-50
Premium winter grade oil. Provides year-round protection and fuel economy. Can be used where SAE 5W-30 is recommended.
Premium multi-grade oil for easier cold-weather starts, maximum protection, excellent fuel economy and added engine life. The preferred grade for most cars built after 1989.
The best selling premium multi-grade in North America. Delivers excellent all-round performance for the average driver.
A premium multi-grade oil for hotter-than-normal running conditions. May provide extended engine life under high temperature conditions.
Thicker premium multi-grade oil for added protection against metal-to-metal contact; specially formulated to meet the needs of high performance European engines.
In many cases, the only thing you need to remember ...
is to look for the PETROCAND logo !