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(951) 780-2743
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The oil and the oil filter need to be periodically replaced. While there is a full industry

surrounding regular oil changes and maintenance, an oil change is a fairly simple

operation that most car owners can do themselves.

In engines, there is some exposure of the oil to products of internal combustion, and

microscopic coke particles from black soot accumulate in the oil during operation. Also

the rubbing of metal engine parts produces some microscopic metallic particles from

the wearing of the surfaces. Such particles could circulate in the oil and grind against

the part surfaces causing wear. The oil filter removes many of the particles and sludge,

but eventually the oil filter can become clogged, if used for extremely long periods.

The motor oil and especially the additives also undergo thermal and mechanical

degradation, which reduce the viscosity and reserve alkalinity of the oil. At reduced

viscosity, the oil is not as capable of lubricating the engine, thus increasing wear and the

chance of overheating. Reserve alkalinity is the ability of the oil to resist formation of

acids. Should the reserve alkalinity decline to zero, those acids form and corrode the

engine.

Some engine manufacturers specify which SAE viscosity grade of oil should be used, but

different viscosity motor oil may perform better based on the operating environment.

Many manufacturers have varying requirements and have designations for motor oil

they require to be used.

Motor oil changes are usually scheduled based on the time in service or the distance

that the vehicle has traveled. These are rough indications of the real factors that control

when an oil change is appropriate, which include how long the oil has been run at

elevated temperatures, how many heating cycles the engine has been through, and how

hard the engine has worked. The vehicle distance is intended to estimate the time at

high temperature, while the time in service is supposed to correlate with the number of

vehicle trips and capture the number of heating cycles. Oil does not degrade

significantly just sitting in a cold engine.

Also important is the quality of the oil used, especially with synthetics (synthetics are

more stable than conventional oils). Some manufacturers address this (for example,

BMW and VW with their respective long-life standards), while others do not.

Time-based intervals account for the short-trip drivers who drive short distances, which

build up more contaminants. Manufacturers advise to not exceed their time or distance-

driven interval for a motor oil change. Many modern cars now list somewhat higher

intervals for changing oil and filter, with the constraint of “severe” service requiring

more frequent changes with less-than ideal driving. This applies to short trips of under

15 km (10 mi), where the oil does not get to full operating temperature long enough to

burn off condensation, excess fuel, and other contamination that leads to “sludge”,

“varnish”, “acids”, or other deposits. Many manufacturers have engine computer

calculations to estimate the oil’s condition based on the factors which degrade it, such

as RPM, temperatures, and trip length; one system adds an optical sensor for

determining the clarity of the oil in the engine. These systems are commonly known as

Oil Life Monitors or OLMs.

Some quick oil change shops recommended intervals of 5,000 km (3,000 mi) or every

three months, which is not necessary, according to many automobile manufacturers.

This has led to a campaign by the California EPA against the 3,000 mile myth,

promoting vehicle manufacturer’s recommendations for oil change intervals over those

of the oil change industry. This is still an active debate within the industry however and

service technicians still recommend 3000 or 5000 miles service intervals in the

conservative North American market, as it suits the customer to have their vehicle

inspected regularly in order to prevent larger problems from developing (for example

slight coolant leaks left unnoticed could lead to an overheat condition). Also, in many

vehicles engine “sludge” from longer oil change intervals has become a problem and led

to very costly repairs sometimes including complete engine overhauls. On top of that

many manufactures are now using turbochargers and lack of proper lubrication is the

primary cause of premature turbo failure. This lack of lubrication is caused by sludge

build up in the oil lines causing restriction of flow.

The engine user can, in replacing the oil, adjust the viscosity for the ambient

temperature change, thicker for summer heat and thinner for the winter cold. Lower

viscosity oils are common in newer vehicles.

By the mid-1980s, recommended viscosities had moved down to 10W-30, primarily to

improve fuel efficiency. A modern typical application would be Honda motor’s use of

5W-20 viscosity oil for 12,000 km (7,500 mi). Engine designs are evolving to allow the

use of low-viscosity oils without the risk of excessive metal-to-metal abrasion,

principally in the cam and valve mechanism.

(951) 780-2743
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