My son purchased new a 2009 Chevrolet Silverado with a 5.3-liter
engine. He’s always used synthetic oil and changed it when the oil
life minder indicates. Recently while on a road trip the oil
pressure dropped to about 10 psi and the low oil pressure light and
stop engine warning came on. He checked the oil level, which was OK.
He restarted and the oil pressure was fine. He drove about another
10-15 miles and the oil pressure dropped again by 15 psi and the
"service engine" light came on. He reduced speed and drove
to the nearest Chevy dealer. They diagnosed a faulty oil pressure
sensor and replaced it at a cost of $463.
Two months and
1,800 miles later, the "service engine" light came on. The
oil pressure gauge read a normal 40 psi. The Chevy dealer where he
purchased the truck found the oil pressure read by a scan tool was
lower than that measured with a mechanical gauge at the filter. They
determined the screen next to the sensor was clogged with sludge.
They replaced it and flushed the engine for $483. Did the first
dealer screw up by not checking and replacing the screen? Is sludge
unavoidable with just a 3-mile commute to work, even with synthetic
oil? The truck had 49,000 miles when these problems occurred. Would
more frequent change intervals help? Or should he plan on doing a
flush every 25,000 miles?
build-up inside an engine occurs when moisture in the air inside the
engine condenses during a cold start and contaminates the oil with
water. Combined with fuel contamination and oil oxidation over time
during normal use, this can form a "glop-like" sludge that
can block or restrict oil passages, screens and filters, causing a
loss of oil pressure. Under normal driving with the engine fully
warmed up, the moisture evaporates and is drawn out through the PCV
system and burned. Short trips after a cold start may not allow the
engine to reach fully operating temperature long enough to eliminate
all this contamination.
So, while the
oil life monitor system may not call for oil changes for 10,000
miles or more, in this case more frequent changes would remove much
if not all of the contamination before it has a chance to jell into
first dealer have caught this? Based on your son describing the
repeat scenario of dropping oil pressure, the pressure sending unit
is suspect but it might have been wise for them to replace the valve
lifter oil filter screen, mounted just below the sensor, at the same
oil changes should prevent additional sludge build-up. According to
TSB 04-06-01-029G, GM does not endorse any type of engine flushing.