NOTE: This article is not
intended to be a full, detailed, explanation of synthetic and petroleum based
oils, NOR, is it intended to be and "End All" to any discussion regarding these
It IS purely an informative
based article based on experiences from RK Tek.
Many ask why RK Tek Inc. does not
recommend synthetic oils in 2 stroke engines?
First, a little history on why
synthetic oils were introduced.
Synthetic oils were invented to help
combat the break-down that a petroleum based oil experiences under a high heat
application/environment (ie. Hot running automobile engines) In other words,
under extreme heat, the petroleum based oil can break-down and cease to properly
lubricate the engine's internal components. This, obviously, can result in
catastrophic engine failure.
Synthetic oils can be chemically
engineered to avoid break-down under extreme conditions. They can also be
engineered to chemically bond to specific metals that are present inside certain
engines. They also stay cleaner.
More detailed info on synthetic oil can
be found at
OK, So, it sounds like this synthetic
oil is the clear winner for high heat applications.
So, why does RK Tek not recommend it in
the 2-Stroke Engine?
The flow and environment of oil in a
4-stroke engine is much different than a 2 stroke engine.
Let's break it down a little......
1) Oil is the main source of cooling.
Its primary purpose is to flow onto, into, and around the piston, cylinder,
crank components, cam components etc. etc. etc.. It keeps these internal
components cool and lubricated and helps avoid excessive heat and friction.
2) Oil is continually re-circulated
throughout the engine. The oil is not given much of a chance to cool down until
the engine is turned off. The oil is always being heated whenever the
engine is running.
3) Oil is constantly be subjected to
"dirty" entities and will capture these entities and become more impure.
There are many more.. but we will stop
here for now..
1) Oil is NOT the main medium for
cooling the engine. The main cooling agent is the fuel.
2) Oil is held in suspension with the
fuel. Meaning the fuel is the vehicle for the oil's travels.
3) Oil is NOT re-circulated. It is
introduced into the engine, does its job and is ejected out of the engine. This
process repeats over and over. This is why you have to add oil after every few
rides. Simply put, the oil does not stick around, it is consumed.
4) Oil is NOT constantly subjected to
the internal engine components. It is not super-heated.
OK, this touches on a few key
differences between the 2 types of engines.
Let's now examine the functions of the
1) Oil remains in the engine and is
pumped to the engine's components. It is a batch system that relies on dedicated
pathways and "Splash" techniques to reach the required components.
2) Oil is constantly heated whenever
the engine is running
3) Oil is re-circulated and requires
frequent purging (oil change) in order to keep it clean.
1) Oil falls out of suspension in order
to perform most of its duties as a lubricating agent.
2) Oil is NOT re-circulated. It is a
waste product. It gets in and gets out.
3) Oil temps are kept very low due to
the constant presence of fuel.
4) Oil forms a light film on the
cylinder wall to keep the piston and rings from seizing to the the bore. In
fact, and this is a strong statement.. If the oil film never breaks-down/fails
you can not have an engine seizure. you can still have engine failure, but not a
5) Oil lubricates the connecting rod,
wrist pin, wrist pin bearing, and crank bearings. These bearings are also kept
cool via FUEL constantly passing over them. Of course, the outer crank support
bearings are not subjected to the fuel.
So, what does all this mean???
It means that the oil of a 2 stroke and
4 stroke engine are introduced to the engine very differently and they are
subjected to much different environments.
It would stand to reason that these
oils are engineered very differently and they are.
Synthetic Oils are engineered to
withstand high heat without chemically breaking-down like their petroleum
2 Stroke Oils are NOT subjected to the
same level of heat of that of a 4 stroke oil.
Fuel, not oil, is the main cooling
agent in a 2 stroke engine.
Oil, not fuel, is the main cooling
agent of a 4 stroke engine.
Due to the method in which the oil is
introduced, and the fact that it is not re-circulated, a synthetic based oil is
not required to avoid oil break-down. The elements that mandate a non petroleum
based oil are simply not present in a 2 stroke engine.
Synthetic oils are much harder to
"burn" Usually, they do not burn. This is a problem is a 2 stroke engine.
Synthetic oil molecules are usually
larger is size and can NOT penetrate (get into) the tiny areas that require
lubrication (like lower rod bearings etc.) Oil penetration is a necessity for
bearing to survive under extreme load/heat.
There is one
argument that many use. It is something like this: "Well, my exhaust valves stay
much cleaner when using synthetic oil". Interesting... Ask yourself, What
does clean exhaust valves have to do with bearing and cylinder lubrication??
Please do not confuse
clean exhaust valves with better lubrication. They are NOT related. In fact, the
fact that the valves are clean lends credibility to the fact that the synthetic
oil is NOT burning/combusting or penetrating small areas but rather just "gliding" over
parts without impregnating in the parts (needed).
Oil must attach itself and penetrate
into the "voids" of your engine. The smaller the oil molecule, the easier it is
for this to happen...too large of molecule (synthetic) and it can not enter the
needed/required areas. OIL is your engine's life blood!!
Here is a VERY good Oil article:
1) BRP/ Ski Doo quit recommending
synthetic oil to be used in their snowmobile engines in 2006.
2) Synthetic Oil can NOT be used to
properly seat piston rings. This is a KNOWN fact to the manufacturers of
synthetic oil. MOST have a non-synthetic "Break-In" oil that is used to properly
break-in a new engine.
3) AND the #1 reason why a synthetic
oil is not as good in a 2 stroke engine--> IT DOES NOT FULLY COMBUST!
Your engine takes the energy from the
combustion process to perform work on the crank train. This energy conversion is
"fueled" from the Fuel/Air/Oil Mixture that it has available during the
The Fuel and the Air will combust and
be converted to energy.
The oil (if Synthetic) will not be
converted to energy because it will usually not combust. So, this "oil" is
taking up "space" in the head that will not aid with any energy transfer.
Basically, DEAD WEIGHT!
Mineral oil WILL combust and aid
in this conversion of energy! So, it's energy is utilized!