Toyota 1996 Avalon, Руководство пользователя

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117
FUNCTIONS OF ENGINE OIL
Engine oil has the primary functions of lu-
bricating and cooling the inside of the en-
gine, and plays a major role in maintaining
the engine in proper working order.
ENGINE OIL CONSUMPTION
It is normal that an engine should con-
sume some engine oil during normal
engine operation. The causes of oil
consumption in a normal engine are
as follows.
Oil is used to lubricate pistons, piston
rings and cylinders. A thin film of oil is
left on the cylinder wall when a piston
moves downwards in the cylinder.
High negative pressure generated
when
the vehicle is decelerating sucks
some of this oil into the combustion
chamber. This oil as well as some part
of the oil film left on the cylinder wall is
burned by the high temperature com-
bustion gases during the combustion
process.
Oil is also used to lubricate the stems
of the intake valves. Some of this oil is
sucked into the combustion chamber
together with the intake air and is
burned along with the fuel. High tem-
perature exhaust gases also burn the
oil used to lubricate the exhaust valve
stems.
The amount of engine oil consumed
depends on the viscosity of the oil, the
quality of the oil and the conditions
the vehicle is driven under.
More oil is consumed by high-speed driv-
ing and frequent acceleration and decel-
eration.
A new engine consumes more oil, since
its pistons, piston rings and cylinder walls
have not become conditioned.
When judging the amount of oil con-
sumption, note that the oil may be-
come diluted and make it difficult to
judge the true level accurately.
As an example, if a vehicle is used for re-
peated short trips, and consumes a nor-
mal amount of oil, the dipstick may not
show any drop in the oil level at all, even
after 1000 km (600 miles) or more. This is
because the oil is gradually becoming di-
luted with the fuel or moisture, making it
appear that the oil level has not changed.
The diluting ingredients evaporate out
when the vehicle is then driven at high
speeds, as on an expressway, making it
appear that oil is excessively consumed
after driving at high speeds.
IMPORTANCE OF ENGINE OIL LEVEL
CHECK
One of the most important points in proper
vehicle maintenance is to keep the engine
oil at the optimum level so that oil function
will not be impaired. Therefore, it is essen-
tial that the oil level be checked regularly.
Toyota recommends that the oil level be
checked every time you refuel the vehicle.
Failure to check the oil level
regularly could lead to serious
engine trouble due to insufficient
oil.
NOTICE
For detailed information on the oil level
check, see “Checking the engine oil level”
in Chapter 7-2.
Facts about engine oil
consumption