Why does oil need to be changed..? • The oil in the engine is contaminated by combustion gases that leak past the piston rings and enter the area below the pistons [crankcase] • These gas vapors are called ‘blow-by gas’
Blow-by gas • 99.9% of blow-by gas is composed of: • Carbon dioxide • Water vapor • The remaining gases are • Un-burnt gasoline • Carbon Monoxide • Oxides of Nitrogen
Un-burnt gasoline • During combustion the gasoline vapors that are very close to the cylinder wall [within .020”] do not burn. • Gasoline dissolves in motor oil. • The oil coating the piston rings absorbs some of the un-burnt gasoline, which is then scraped off the cylinder wall by the oil control ring and returned to the oil pan. • Additives in the motor oil prevent the un-burnt gasoline thinning out the oil.
Acid formation • There is always a small amount of sulfur in all petroleum fuels. • The sulfur in the un-burnt gasoline reacts with water in the blow-by gas to form sulfuric acid. • Nitrogen monoxide reacts with water in the blow-by gas to form nitric acid. • The sulfuric and nitric acid are absorbed by the engine oil turning it acidic.
Corrosion inhibitors • To prevent engine damage chemical additives in the motor oil function to bond with these acids thereby neutralizing them. These additives are called corrosion inhibitors. • After several thousand miles of driving the corrosion inhibitors are saturated and can no longer protect the engine. • Acid in the oil will attack the metal in the engine, especially the soft metals used in engine bearings.
Other additives • There are several other chemicals additives: • Detergents - help prevent the build up of varnish • Dispersants - help absorb water • Anti-scuff agents - help maintain an oil film between surfaces in sliding contact • Extreme pressure agents - help prevent the oil from being squeezed out of the gap between the bearings and journals when operating at high power levels • Viscosity index improvers - help oil flow at low temperatures and prevent oil from thinning out at high temperatures
Oil change interval • To get rid of all the byproducts of combustion [acid, water, dirt, sludge etc.] that gets absorbed by the oil the manufactures set recommended oil change intervals based on mileage and time. • Vehicles that are driven on short trips and spend a large percentage of time warming up need to have the oil changed at frequent intervals. • During the first few minutes after a cold start the clearance between the piston and cylinder wall are greater – allowing a higher percentage of blow-by gas to leak past the piston rings.
Oil change interval • When the engine is cold the air fuel ratio is higher (numerically lower). • The excess gasoline condenses on the cool cylinder walls where it is scraped off by the piston rings and ultimately ends up in the crankcase. • Vehicles that spend a lot of time on the highway do not require the oil to be changed as frequently as vehicles that a driven on shorter trips.
Oil change interval • The normal service schedule in AllData will also list all other services and checks that should be performed with the oil change. • The manufacturer also publishes the oil change interval in the owners manual. • The oil change interval can be found in AllData
Normal and severe operation • Typically manufactures publish two service interval specifications: • Normal operation is defined as: • daily driving of 10 or more miles each day • Severe operation is defined as • Short trips less than 10 miles • Prolonged idling periods • Stop and Go driving – taxi cabs etc. • Towing a trailer • Driving in dusty conditions [dirt roads, desert driving]
Oil change reminder light • The best way to determine when to change oil is to utilize the oil change reminder light that is found on most newer cars. • The PCM [engine computer] uses a sophisticated algorithm that looks at engine temperature, engine rpm and engine load every second of engine operation to calculate when the engine oil has reached the end of its useful life. • In order for this system to work properly the oil reminder light must be reset each time the oil is changed. Reset button
Oil reminder reset procedure • Each manufacturer has it’s own reset procedure. • If the reset button is in the under hood fuse box the procedure may be printed on the fuse box cover. • If there is no placard under the hood the procedure can be found in AllData under • Maintenance – Service Intervals – Maintenance Indicator Reset
Oil color • Oil color is not a good indicator of oil condition unless the oil is way past due for an oil change. When the oil turns chocolate brown it has begun to turn into sludge and is well overdue for an oil change After a few hundred miles of driving the oil picks up carbon black and begins to turn dark grey Fresh oil has a slight amber color
Oil viscosity • Oil viscosity is a measure of how easily the oil flows at a given temperature. • Resistance to flow can be measured with a Viscocimeter. • Oil naturally tends to be thicker at lower temperatures and wants to thin out at higher temperatures. • Engine oil must be thick enough to prevent metal to metal contact between the crankshaft journals and the bearing surfaces. • Important Properties of Engine oil: Lubricate>Clean>Cool>Cushion>Seal (LCCCS) • Since the oil also acts as a coolant to transfer heat away from the pistons, valves and bearings it must be thin enough to flow rapidly throughout the engine.
Viscosity 0 degrees F. 210 degrees F. • A simple method of measuring viscosity is to measure the amount of oil that can flow through a funnel in a fixed amount of time
Multi viscosity oil • If the oil is too thick the fuel efficiency will be reduced. • If the oil is too thick the engine will be difficult to crank over when the outside temperature is below freezing. • Nearly all cars manufacturers specify a multi viscosity oil that has additives that allow it to flow better when it is cold and remain thick enough to protect the bearings when hot. • Multi-Viscosity oils are engineered to counteract the thinning that happens as it heats up.
Multi viscosity index numbers • Multi viscosity oil has two sets of numbers in the viscosity index • The first set indicates the cold viscosity index • The second set indicates the hot viscosity index • The letter ‘W’ usually follows the first number indicates that this oil is suitable for winter driving • An SAE 10W-30 oil • Has a viscosity of 10 at 0 deg. F • Is suitable for winter driving • Has a viscosity index of 30 at 210 deg. F
Using a different oil viscosity • The manufacturer sets the oil viscosity for general driving in all regions of the country • Cold viscosity • If the temperature of the region is not expected to go below 32 deg F an 20w–xx oil can be used • If the temperature is expected to drop below 32 degrees F but not below 0 degrees f a 10w–xx oil may be used • If the temperature is expected to drop below 0 degrees F a 0w-xx oil should be used
Using a different oil viscosity • The manufacturer selects the hot viscosity based on normal driving and best fuel economy • Hot viscosity • If the engine is going to be working hard [towing etc.] and fuel economy is not an issue ten points can be added to the hot viscosity. • If the engine is burning oil changing to an oil with a high temperature viscosity 10 points higher may decrease oil consumption but will increase fuel consumption slightly. • Under no circumstance should you ever use an oil with a lower hot viscosity than the manufacturer recommends.
API service grade • The American Petroleum Institute sets standards for the type and amount of additives used in motor oil • The API service grade consists of two letters sometimes followed by a number • The first character is either an ‘S’ or a ‘C’ • ‘S’ for ‘spark’ indicates an oil to be used with gasoline engines • ‘C’ for ‘compression’ indicates an oil formulated for diesel engines
API service grade • The second letter is the performance level which changes every few years as manufactures demand better protection. • The current grade for gasoline engines is SN which meets performance criteria for 2011 and newer cars • SM can be used in engines built in before MY 2010 • SL is suitable for engines built in or before MY 2004 • SJ is suitable for engine built in or before MY 2001 • SH and lower are obsolete • API grade are backwards compatible so ‘SN’ oil is safe to use on any model year engine
ILSAC • The International Lubricant Standardization and Approval Committee is a world wide organization that sets standards similar to API • The current oil standard for gasoline engines is GF-5
Oil for diesel engines • The API service grade for diesel engines starts with the letter ‘C’ – compression ignition • Engines manufactured in MY 2010 and later require ‘J’ level oil • ‘I’ was introduced in 2002 and was used through 2009 • ‘H’ was introduced in 1999 and was used through 2001 • Motor oil for diesels usually has a number following the two letters • The number indicates whether the oil is suitable for 2 stroke or 4 stroke diesel engines • The internal components of 2 stroke diesel run at higher temperatures than comparable 4 stroke engines
Oil for late model diesel engines • CJ-4 • The first letter - ‘C’ indicates a Diesel engine • The second letter - ‘J’ indicates the oil is suitable for engines produced in 2010 or later • The number - 4 indicates that the oil is suitable for high speed 4 stroke diesel engines* A high speed diesel engine is designed to run at speeds of over 1000 rpm Medium speed engines run a max speeds between 300 and 1000 rpm Low speed diesel engines run at speeds below 300 rpm
Labeling • Every oil container should clearly show the SAE viscosity index, API grade and ILSAC grade ACEA is a European standard for motor oil
Oil Filters • Modern oil filter use a porous folded paper filter element to trap dirt particles. • There are currently two types of oil filters used on modern engines • Spin on • Cartridge Spin-on Cartridge Photo courtesy of Federal-Mogul Corporation
Cartridge type oil filter • The cartridge type filter is an environmentally friendly alternative to the Spin-on type filter • The elimination of the disposable metal shell permits the recovery of nearly all of the used oil during oil changes Photo courtesy of General Motors Corporation
Spin on oil filter Oil outlet - threaded Oil inlet O-Ring seal Anti-Drain back valve Paper filter element Disposable metal shell - bust strength of approximately 100 psi Flats for filter wrench Bypass valve Photo courtesy of Federal-Mogul Corporation
Oil filter change interval • Oil filters normally last much longer that the engine oil • Since the oil filter is very inexpensive it is normally changed every time the oil is changed
Always use fender covers • A clean fender cover protects the fenders and grill from oily handprints and scratching • Your future employer will insist that you always use them • Now is a good time to get into the habit
Before you start • Oil should be drained when the engine is hot if possible • The temperature the oil directly after engine shutdown is around 180 degrees F. – this is hot enough to burn your skin • Allow the engine to cool for 5 to 10 minutes before removing the drain plug
Before you start • Before setting up the car on the lift open the hood when your hands are clean – this way the won’t get oil stains on the hood or hood release lever • Before draining oil check to see if the oil drain container is is more than ½ full – if so, empty it into the waste oil recycling tank • Most manufactures recommend removing the oil filler cap prior to draining the oil
Drain Plug • The drain plug is located at the bottom of the oil pan and is typically a 14 to 19 mm hex plug
Position the catch pan under the drain • Raise the catch pan so that it is about 12 inches below the drain plug • Position the catch pan in the path of the anticipated oil flow
Position the catch pan under the drain • Remove the drain plug and allow the oil to drain untill any remaining oil drips out at the rate of one drop every 5 seconds or longer • With the oil draining reposition the oil drain to catch any oil as the filter is removed
Locate and remove the oil filter • Most oil filters are mounted on the side of the engine block and are easily accessible from underneath the vehicle
Remote oil filter • In some applications there is no room for the filter at the bottom of the engine to mount the filter so a filter housing is bolted to the block that allows the filter to be mounted at the top of the engine Oil pressure sending unit Oil Filter Adapter assembly Photo courtesy of General Motors Corporation
Remote oil filters • Some trucks locate the oil filter[s] on the inner fender or firewall • High pressure rubber hoses connect the oil filter housing to the engine block
Oil filter wrench • The cup type wrench shown here engages the flats on the bottom of the filter • A 3/8” drive ratchet attaches to the square hole in the center of the cup
Band type filter wrench • The band type wrench fits a number of different filter diameters but does not fit into tight places
Draining the filter • The filter should be placed upside down in the oil drain pan for 12 hours if the engine is hot and 24 hours if the engine is cold. • Puncturing the domed end of the filter will make the filter drain faster • After all of the oil has drained out the filter can be disposed of with normal [non-hazardous] shop waste
Clean the o-ring boss on the engine • The surface that the o-ring seals against must be clean • Wipe the flat surface that contacts the o-ring to make sure there are no chunks of old o-ring material or dirt
Lubricate the O-Ring • Dip your finger in some fresh oil and smear it around the o-ring
Install the filter • Some mechanics will fill the filter with new oil prior to installation • This reduces the time that engine runs with no oil pressure during initial startup • If a cup type filter wrench is available the filter can be torqued to specifications • Otherwise an additional ¼ turn with a filter wrench is needed
Replace the drain plug washer • The drain plug washer [gasket] should be replaced whenever the oil is changed • A fresh washer creates a better seal and requires less torque to achieve a tight seal
Install the drain plug and washer • The torque value listed in AllData is only valid if a new washer is installed • If the old washer is reused more torque will be needed to seal it • Eventually the amount of torque needed to seal the washer will begin to damage the threads in the oil pan drain hole
Determine the oil capacity • Before adding oil find the correct oil capacity in AllData • The oil capacity may also be found in the owners manual • The oil capacity is usually not found anywhere under the hood • If the oil capacity is not know start with 3 ½ quarts then check the dipstick - then add ½ quart at a time until the dipstick reads full
Use a funnel to minimize spillage • Hold the container sideways to prevent the oil surging as air enters the bottle. • When the container is upright the amount of oil remaining can be measured by finding the liquid line through the transparent window on the side Transparent window