Over the past year or so, many auto dealers and service
shops have noticed that they are having many more customer complaints about so
called ?drivability issues? including hard starting, engine knock, hesitation,
stalling, rough idle, poor fuel economy, and even misfiring.
Most of these problems are related to the buildup of
varnish deposits in the fuel injectors and throttle body and carbon deposits on
the intake valves and in the combustion chamber. This buildup is directly
related to the very significant reduction in the use of detergent-dispersants by
many of the major refiners.
These problems were common in the late 80?s and early
90?s until the EPA forced refiners to add Detergents to meet a ?Lowest Additive
Concentration? requirement. This level although lower than many experts felt
necessary seemed to resolve the problems for a time.
Depending on who you talk to, it is suggested that
starting around 2001 refiners have been reducing the use of these
detergent-dispersants by 40%-66%, that?s up to a 2/3 reduction. This was made
worse by additional reductions allowed and encouraged by the EPA in the wake of
the 2005 hurricane season to alleviate spot shortages caused by the damage these
storms did to our overall refining capacity. These reductions in the additive
level and octane rating may save the refiners money and possibly increased
supply, however it causes many engine problems, raises emissions, and lowers
mileage for the users of their fuel.
It is also suspected that some oil companies (but not all) used this opportunity
to cut back their use of detergents and deposit control additives even further
in their gasoline's.
Because nearly all of today?s engines have knock sensors
and other computer controls, they can adjust to somewhat lower quality fuels.
However as the computer retards the ignition timing to control knock, it reduces
horsepower, raises emissions, and reduces fuel mileage. Some engines,
particularly those with higher compression ratios can suffer physical damage if
they use low quality gasoline over a long period of time.
To the best of our knowledge there have not been any recent studies by the
government or anybody else that addresses the issue of the quality fuels
currently being produced and whether the level of detergent and deposit control
additives in gasoline is sufficient to keep today's engines clean. It is
reasonable to assume that if such a study were undertaken now, it would have
reveal significant and widespread problems with inadequate levels of these
necessary additives in most gasoline's.
When deposit control additives (detergent-dispersants) are not used at adequate
levels in gasoline, harmful deposits can build up inside the engine:
Fuel varnish deposits that
form inside the injectors which 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 also distort the spray pattern of
the injectors which causes uneven atomization of the fuel. This in turn causes
poor fuel ignition and burning which leads to rough running, lower power, higher
emissions, and higher fuel consumption. 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 build up.
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.
Deposits that form on the
intake valves can restrict airflow through the intake ports, causing a loss of
high speed power. The deposits also can 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 also
can 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 the guides.
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 PCM to
retard spark timing. This will take care of the knock, but retarded timing also
increases fuel consumption and emissions.
A buildup 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 high load), pre-ignition can burn a hole right through
the top of a piston!
A condition known as Combustion Chamber Deposit Interference (CCDI) also can
occur when the carbon deposits are so thick the deposits on the piston and head
make physical contact. This area, known as the Squish Area (piston to top of
chamber), has a clearance that is about as thick as a paper clip. This can cause
a loud, metallic banging sound when a cold engine is first started. The deposits
are soft and will gradually flake off. But the flakes may lodge between the
valves and seats causing a loss of compression, misfiring and rough running when
the engine is cold (a condition called Combustion Chamber Deposit Flaking or
The formation of harmful deposits can be controlled by adding
detergent-dispersants to gasoline, the most common of which is polybutene
succinimide. Used with a petroleum carrier oil, detergent-dispersants help keep
the intake manifold and ports clean. These chemicals are more effective than the
carburetor detergents that were once used in gasoline, but they must be used at
concentrations that are three to five times higher than the older carburetor
Deposit control additives such as polybutene amine (PBA) were introduced in 1970
to help keep injectors and intake valves clean. The only drawback with PBA is
that too much of it can increase combustion chamber deposits. Polyether amine
(PEA), by comparison, cleans fuel injectors and valves, and does not increase
combustion chamber deposits. In fact, it helps remove accumulated deposits
inside the combustion chamber to reduce the risk of spark knock. In 1995, the
U.S. Environmental Protection Agency set minimum standards for additives in
gasoline to prevent the formation of deposits in fuel injectors. Gasoline
refiners had to certify that their additive packages met these standards, but
some experts now say the original standards were set too low and do not provide
adequate protection with some fuels and engines. The minimum EPA-required level
is referred to as the "Lowest Additive Concentration" (LAC), and is typically
found in the cheapest priced gasoline.
At the other end of the fuel quality spectrum are "Top Tier" gasoline's. These
fuels are recognized by the vehicle manufacturers as having the most effective
additives and in the highest concentrations. Gasoline retailers must meet the
high Top Tier standards with all their grades of gasoline (not just premium) to
be designated a Top Tier supplier. In addition, all the gasoline outlets
carrying the brand of approved gasoline also must meet the same standards. There
are very few refiners that meet this qualification.
Unfortunately, fuel quality isn't something that is easily policed. Many states
have programs in place to monitor fuel quality on either an ongoing basis or
"incident specific" basis. Most are run by the state's Department of Weights and
Measures. Even so, the focus of most of these programs is to make sure consumers
aren't being cheated at the pump and get the full gallon they pay for. Some
programs also check fuels to make sure they do not contain too much alcohol. The
specific density of gasoline can be field tested to determine its volatility and
alcohol content. But testing octane and the amount and type of additives in the
fuel requires expensive laboratory testing. So this type of quality testing is
According to some industry experts, many gasoline marketers have reduced the
concentration of fuel additives in their fuel up to 50% in recent years!
Most gasoline refiners don't want to sell the public bad gas because they
obviously want repeat customers. Generally though they know that deposit
formation is a gradual thing that occurs over time. So if they cut back on the
additive package to save a few cents per gallon, nobody is likely to find out
and it can be explained away until hard evidence is found. This hard evidence is
expensive and time consuming to obtain. The only agency likely to be able to do
this is the Federal Government via the EPA. Even if they decide to do this
today, it will likely take years to complete and more years to do anything about
it. In the meantime refiners will pocket millions of dollars in savings.
People who buy the cheapest LAC gas they can find every time they fill their
tank will sooner or later have problems. The low level of additives (or low
quality additives) in the fuel will not be adequate to keep their engine clean,
and eventually they'll start to experience drivability problems and or actual
More seriously, if a bad batch of fuel leaves a refinery and ends up in people's
vehicles, it can cause even more expensive problems. There have been several
instances in the past several years where too much residual sulfur in a bad
batches of gasoline has caused a rash of fuel pump and gas gauge sending unit
Immediate drivability problems also may occur if the fuel is contaminated with
water contains too much alcohol or the wrong type of alcohol (methanol instead
of ethanol). Alcohol is a great octane booster, but for ordinary gasoline the
amount of ethanol should not exceed 10% (or 5% for methanol). Note: Ethanol
is being used extensively to replace MTBE as an oxygenate in motor fuels.
The only exception here is G85 fuel for "flex-fuel" vehicles that is 85% ethanol
and 15% gasoline. G85 contains considerably less energy per gallon than gasoline
and runs much leaner, so the vehicle must have a special fuel sensor so the PCM
can compensate for the alcohol to maintain the proper air/fuel ratio. G85
contains only about 75% of the energy found in regular gasoline, so be prepared
to go to the pump more often.
Getting Rid of Deposits
When a vehicle is experiencing deposit-related drivability, performance or
emissions problems, the deposits have to be removed. There are several ways
troublesome deposits can be removed. One cost-effective solution to
deposit-related drivability issues is to simply add a can of fuel system cleaner
such as Ultra-X, Xcelerate, or Power Up to the fuel tank. The cleaner will
slowly remove the deposits while the vehicle is driven. The only drawback with
this approach is that it takes time - maybe one or two tankfulls with the
additive to make a noticeable difference. That may be too long for some people.
For those who want an immediate fix, the best option usually consists of
cleaning the throttle body with an aerosol cleaner, flushing the injectors with
a concentrated solvent or cleaning product, and/or feeding an intake system
cleaner of some type into the engine while it is running to clean the intake
ports, valves and combustion chamber.
Remember, it is far better to dissolve deposits as
opposed to breaking them up. The last things you want is have chunks of hard
carbon floating around anywhere in your engine.
To prevent the formation of new deposits once the engine has been cleaned, you
should recommend using a top tier gasoline or adding a bottle of fuel system
cleaner as Ultra-X, Xcelerate, or Power Up periodically to the fuel tank (say
every four or five fill-ups or when changing the oil every 3,000 miles) or by
treating your bulk fuel with OctiPlus.
Fuel Cleaning Additives Not the Same
One very important point to keep in mind about aftermarket fuel system cleaners
that are added to the gas tank is that they use different chemistries to achieve
different results. As mentioned earlier, some chemicals used in low cost
additives such as PBA can clean injectors and valves but may actually increase
combustion chamber deposits. Other chemicals slightly more expensive components
such as PEA can clean the entire fuel system as well as the combustion chambers.
For dirty fuel systems, you should use a product that is concentrated enough to
provide some real cleaning action (OctaPlus). But for maintenance, you only need
a product that keeps deposits from forming (OctaPlus).
OctiPlus and Ultra X fuel system cleaning product does something that no other
product does. They actually clean and protect the contacts on fuel gauge sending
units. The contacts on the sending unit are typically plated with
silver-palladium to resist corrosion. But over time, residual sulfur in gasoline
can corrode the contacts causing the gauge to rear erratically or not at all.
Replacing the sending unit is an expensive job because you have to drop the fuel
tank, so a more affordable alternative is to simply add a bottle of this product
to the tank or to treat your bulk fuel and let it take care of the corrosion.
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