Motor oils is more than just an engine lubricant. It coats surfaces like the crankshaft journals, cylinder walls, valve lifters, camshafts, etc with a liquid bearing surface. it’s a coolant that helps transfer heat from the engines moving parts to the engine cooling system. It’s a liquid shock absorbing medium that helps cushion the rotating and reciprocating engine parts. It’s a cleansing agent that prevents rust and corrosion from building up inside your engine. Motor oils have come a long way since I started working on cars and trucks some fifty year ago. Those were the days when the 3,000 mile oil change was the rule. Today, with all the new synthetic oils, many companies are promoting 7,500 to 10,000 mile oil change intervals but should go that long between oil changes? It all depends on how you drive your car, for most people the 3,000 mile oil change is still the best rule to live by. Before we get into the why of that lets take a minute to discuss what you should know about motor oils.
Viscosity, simply put, is an indication of how easily an oil pours at a given temperature. Viscosity is often referred to as “weight” and is indicated by a number assigned to it by the Society of Automotive Engineers testing laboratories and is referred to as the oil’s SAE. number i.e. SAE 5W-30. The “W” in the viscosity rating refers to the oils “winter” or cold weather viscosity. 5W-30 is a multi-viscosity oil that changes viscosity with temperature. As the ambient temperature increases and/or as the engine get hotter the oil’s viscosity increases, the oil becomes thicker which makes them a more efficient lubricant at higher temperatures. There are single viscosity oils but they aren’t of much interest to the general motorist. The most common multi-viscosity oils today are 5W-30, 10W-30, 15W-40 and 20W-50weights. Which viscosity oil is best for your engine? You can find that information in your owners manual and/or stamped on the oil filler cap. A good rule of thumb is to use 5W-20 or 5W-30 for overhead cam engines and 10W-30 oil for engines with pushrods and lifters. Overhead cam engines require a thinner oil to speed up the lubrication of the overhead camshafts.
Roughly 25 percent of every quart of motor oil consist of motor oil additives. These motor oil additives serve to extend the viscosity range and the life of the actual lubricant. Additives extend the viscosity range of the oil, allow it to withstand high pressures and loads, handle contaminants in the crankcase, and reduce friction for improved fuel economy. It’s the motor oil additives that actually determine the performance rating of the motor oil. A few of the many additives are a Viscosity Index (VI) Improver, antioxidants that prevent the oil from burning when it gets hot and prevents carbon formation, there are detergents that help keep your engine clean, antiwar inhibitors, rust and corrosion build up inhibitors, and antifoaming additives, just to name a few.
Synthetic motor oils are a more highly refined lubricant with many additional additives to protect today’s high performance. hard working engines and they are well worth the money they cost but they are no substitute for performing oil changes based upon the way you drive and based upon the driving conditions under which your car or truck operates. The 7,500 to 10,000 mile oil change cycle that most manufacturers of synthetic oils propose are based upon ideal driving conditions and not on the way most of use drive. For us average drivers, usage falls under the umbrella classification of “severe service” and the 3,000 mile rule applies.
1. Most trips are less than 4 miles.
2. Most trips are less than 10 miles when outside temperatures remain below freezing.
3. Prolonged high speed driving during hot weather.
4. Idling for extended periods and continued low speed operation (as when driving in stop-and-go traffic).
5. Towing a trailer.
6. Driving in dusty or heavily polluted areas.
If you car or light truck is diesel powered the 3,000 mile oil change and 10,000 mile filter change is mandatory because diesel engine have a higher amount of blow-by than gasoline engines and require more frequent oil and filter changes.
1. Change the oil while it’s hot. Hot, free flowing oil will carry more of the oil pan sludge and other contaminants out with it.
2. Always replace the oil filter when you change the oil because many of the contaminants held in the filter are able to contaminate the new oil.
3. Make sure that the oil filter to engine mating surfaces are clean and then coat the new oil filters gasket with clean oil. Most people think that this helps the gasket seal better and it may but the real reason for coating the gasket with oil is to keep it from seizing to the engine and ripping as the filter is tightened and later removed.
4. Hand tighten the new filter for ½ to ¾ turn after the filter gasket makes contact. Over tightening can damage both the threads as well as the filter gasket. Under tightening allows for leaks.
5. If the old oil was badly sludged or contaminated the engine crankcase should be cleaned and flushed before new oil is added.
6.Must engines take about four quarts of oil with an additional half-pint to one quart for the filter. Check your owner’s manual or a service manual for the correct amount of oil to use.
7. After pouring in the new oil, run the engine for twenty minutes and check for filter leaks. Stop the engine and check the oil level. If necessary, add oil to bring the level up to the full mark.
8. Don’t overfill. Overfilling causes the oil to foam and it causes oil leaks by putting excessive pressure on seals and gaskets. Foaming oil also looses its lubricating ability which leads to bearing and cylinder damage.
9. Running with the crankcase under filled can cause a loss of oil pressure and engine damage.
