"What brand or grade of Gas should I put in my
car?" or "My car is running rough at idle, maybe it
needs a tune up." I am confronted with these
Your car runs on gasoline, the manufacturer and
its engineers specifies what grade and minimum
octane rating of your car. Your car was
engineered and programmed accordingly. Not all
gasoline are the same. You get what you pay for
A penny saved at the gas station will cost you
ten dollars at the repair shop next week.
Since the minimum additive performance standards
were first established by EPA in 1995, most gasoline
marketers have actually reduced the concentration
level of detergent additive in their gasoline by up
to 50%, leading to carbon deposits on fuel
injectors, intake valves, and combustion chambers,
which can have a big impact on in-use emissions and
retailers provide fuels with lower-quality additive
packages that can build up deposits on fuel
injectors and on intake valves.
When deposit control
additives are not adequate in gasoline, harmful
deposits can build up inside the engine:
* Fuel varnish deposits that form inside the
injectors restrict fuel delivery and cause the
engine to run lean. This may cause lean misfire,
rough idle, hesitation, poor fuel economy and
increased HC emissions. A lean fuel mixture also
increases the risk of detonation and pre ignition.
These deposits tend to form during the heat soak
period that occurs after the engine is shut off. The
shorter the trips and the more frequent the drive
cycles, the faster these deposits buildup.
* Deposits that form in the throttle body can
reduce airflow through the idle bypass circuit
affecting idle quality and smoothness. These
deposits are formed by fuel vapors that rise up
through the intake manifold.
Intake valve deposits from gasoline that does
not contain enough detergent
* Deposits that form on the intake valves can
restrict airflow through the intake ports, causing a
loss of high speed power. The deposits can also act
like a sponge and momentarily soak up fuel spray
from the injectors. This disrupts the mixing of air
and fuel causing a lean fuel condition, hesitation
and reduced performance. Deposits can also cause
valve sticking and valve burning. Intake valve
deposits are formed by normal combustion byproducts,
but may build up more rapidly if the valve guides or
seals are worn and the engine is sucking oil down
* Deposits that form inside the combustion
chamber and on top of the pistons increases the
compression ratio of the engine and the octane
requirements of the fuel. Too much compression can
cause spark knock (detonation) if the fuel's octane
rating isn't high enough. Over time, detonation can
damage the head gasket, piston rings and rod
bearings if it is not controlled. The knock sensor
will detect detonation and tell the computer to
retard spark timing. This will take care of the
knock, but retarded timing also increases fuel
consumption and emissions.
A build up of carbon deposits inside the
combustion chamber also increases the risk of hot
spots forming that may cause engine-damaging pre
ignition. The hot spot ignites the fuel before the
spark plug fires, causing a sharp rise in combustion
pressure. Under extreme conditions (high rpm and
load), pre ignition can burn a hole right through
the top of a piston!
Six of the world's
top automakers, BMW, General Motors, Honda, Toyota,
Volkswagen and Audi recognize that the current EPA
minimum detergent requirements do not go far enough
to ensure optimal engine performance. They developed
a TOP TIER Gasoline standard requirement.
have raised the bar. TOP TIER Detergent Gasoline
help drivers avoid lower quality gasoline which can
leave deposits on critical engine parts, which
reduces engine performance. That’s something both
drivers and automakers want to avoid.
manufacturers have issued special service bulletins
advising their dealers of this issue.
Just remember, you
will spend at the repair shop a lot more than what
you are saving at an inexpensive gasoline station.
retailers known to be on the TOP TIER list are shown
MFA Oil Co.
The Somerset Refinery, Inc.
Kwik Trip / Kwik Star
Tri-Par Oil Co.
Turkey Hill Minit Markets