INTRODUCTION

Fuel is the second highest expense in vehicle operation amounting to about 18 to 25% of total life costs (TLC). (Depreciation is the highest vehicle expense)

If however you have operated a heavy duty long haul truck over the same period (1990-2002) that used on the average 17,000 gallons of diesel fuel annually, than the fuel saving would have been about $850 per year.

The above costs were calculated on historical costs for vehicles purchased in 1990 and used for 12 years through 2002. For that period the average cost per gallon of unleaded gasoline in USA was about $1.47 per US Gallon. Today the unleaded regular grade of gasoline averages over $2.00 per US Gallon, and the cost of diesel fuel has also doubled.

If however you operate a heavy duty long haul truck that uses on the average 17,000 gallons of diesel fuel annually, than the fuel saving will be currently about $1,700 per year.

The explanation is simple, the less energy you consume to move or operate a given mechanism, the less power you need to drive it, which in turn means that in a vehicle you need to burn less fuel to do the same work.

Consider this, sophisticated computer simulations show, that you can improve mileage by over 0.5 MPG just by reducing continuous power consumption by a half horsepower.

This is why more and more accessories are being powered by electric motors, so there is no constant drag of mechanically driven pumps for intermittent devices or fans for cooling that are not required most of the time.

Although there are millions of drivers and thousands of mechanics, only small fraction of them knows or can answer this question about Fuel.

First of all you know that when there is no Gasoline in the gas tank that the car stops, therefore fuel is necessary for engine operation. Gasoline contains virtually hundreds of different chemicals, the major proportion of which are known as Hydrocarbons.

Hydrocarbons are chemical compounds consisting solely of Hydrogen and Carbon atoms.

The second component that you need to make the car go is Air.

You may know from experience that if the Air Filter is dirty or clogged that the car does not run as well or is impossible to start. Likewise if you plug up the Air Intake the engine will stop. Therefore Air is also necessary for engine operation.

The Air that we breathe and the Air that is also used in the automobile engine is a mixture (by volume) of:

Unfortunately due to rapid revolution of the typical engine and less then ideal mixing of Fuel and Air, the actual combustion in typical engine is far from perfect. As a result we have Air Pollution, Smog, and laws that insist on "clean" exhaust from modern vehicles.

Since combustion and complete burning in conventional engines is difficult to achieve, engineers have for over 30 years resorted to "after-treatment" hence we now have catalytic converters, unleaded fuel, low sulfur fuel, etc.

The Otto engine is an internal combustion engine, which converts the chemical energy contained in the fuel (usually Gasoline) into a kinetic energy by burning it (rapid oxidation).

The energy conversion is carried out by combustion of the hydrocarbons in the Fuel. There is one important thing to understand about the hydrocarbon fuel, such as Gasoline, in reference to combustion. That is, it is the energy stored in the chemical bond within the hydrocarbons themselves that is released when these compounds burn in the presence of Oxygen inside the combustion chamber. This released energy is Heat.

The internal combustion engine is therefore a Heat Engine, and it is the Heat inside the engine that is converted into a useful kinetic rotary motion by mechanical means.

The combustion process in the Otto engine is initiated by electric spark within the combustion chamber after the Air/Fuel mixture was compressed.

The picture below shows some key components of the Spark Ignition Engine:

The combustion Heat given off increases the pressure of the pre-compressed gasses. This after-combustion pressure is typically 400 to 700 PSI, which is much higher than the pre-combustion pressure of 95 to 155 PSI. (PSI = Pounds per Square Inch)

This high pressure produces mechanical work by forcing the Piston down and via Pin and Con Rod causes the Crankshaft to turn.

After each Power Stroke the burnt gases are expelled by the Piston's upward motion and discharged into the atmosphere past the Outlet Valve through Exhaust tract.

The exchange of gas in the 4-stroke spark ignition engine is controlled by Valves, which open or close the Inlet and Outlet ports of the Cylinder, depending on the position of the Piston and the Crankshaft. The opening and closing period of the Valves is in turn operated by Camshaft, which turns at one half the speed of Crankshaft.

· Inlet Valve: OPEN

· Outlet Valve: CLOSED

· Piston Movement: DOWN

· Combustion NONE

The downward movement of the Piston increases the volume of the combustion chamber, enabling a fresh Air/Fuel mixture to be sucked past the open Inlet Valve into the Cylinder.

· Inlet Valve: CLOSED

· Outlet Valve: CLOSED

· Piston Movement: UP

· Combustion NONE

The upward moving Piston reduces the volume of the combustion chamber thereby compressing the Air/Fuel mixture. The compression factor is approximately from 6 to 14, according to the type and design of the engine. The final compression pressure is from 85 to 190 PSI.

· Inlet Valve: CLOSED

· Outlet Valve: CLOSED

· Piston Movement: DOWN

· Combustion YES

The compressed Air/Fuel mixture is Ignited by the Electric Spark at the Spark Plug electrode gap. As the mixture is rapidly burnt its temperature also rapidly increases, typically to about 5,000° F to 6,000° F. As a result the pressure in the Cylinder rises to between 400 to 600 PSI.

The pressure of the combustion gasses drives the Piston downwards in the Cylinder and by means of the Con Rod (Connecting Rod), produces rotary movement of the Crankshaft.

· Inlet Valve: CLOSED

· Outlet Valve: OPEN

· Piston Movement: UP

· Combustion NONE

The upward moving Piston reduces the volume of the combustion chamber, whereby the burnt gases (exhaust) are expelled through the open Outlet Valve and through the Exhaust tract to the atmosphere.

In practice on most engines an Exhaust Muffler or a Silencer is used to dissipate a high kinetic energy that is present in the exhaust gases and which would otherwise cause uncomfortably loud noise.

In other applications the exhaust gasses are expanded in a high-speed turbine (Turbocharger) and the recovered energy is used for supercharging of the Intake with Air/Fuel mixture at higher than atmospheric pressure (Turbo Boost). This method is frequently used in high performance cars and high altitude piston engine aircraft.

The stroke cycle repeats itself after the Fourth stroke. In the actual cycles of the internal combustion engine the opening times of the Valves are synchronized to the movement of the Piston and to the rotation of the Crankshaft by the use of Camshaft(s), Push Rods and or Rockers.

Each cycle of the four strokes employs two rotations of the Crankshaft and one rotation of the Camshaft(s).

Unfortunately, higher Octane Gasoline costs more to produce than low Octane Gasoline. Therefore the increase in fuel efficiency can be offset by increase in fuel costs.

The Compression Ratio is based on the mechanical design of the engine and is expressed as:

When the Final Compression Pressure is too high on a used engine, it usually means that the combustion chamber and the piston crown have excessive amounts of carbon deposits that have been formed due to any of the following:

If the Final Compression Pressure is too low on a used engine, it usually means that the engine has any of the following problems:

For the quality of the combustion process it is of prime importance that the fuel mixes intimately with the air, so that it can be burnt as completely as possible. It is important that the flame front progresses spatially and in regular form during the power stroke, until the whole mixture has been burnt. The combustion process is considerably influenced by the point in the combustion chamber at which the mixture is ignited, and by the mixture ratio as well as the manner in which it is fed into the combustion chamber.

Combustion is optimal and the efficiency of the engine is at its best when the residual gases contain no unburned fuel and as little of Oxygen as possible. The Hydrocarbons are broken up during the combustion into their constituent parts, they are Hydrogen and Carbon. On complete combustion the Carbon and Hydrogen burn to form Carbon Dioxide and Water vapor. When the combustion is incomplete the exhaust gases also contain other undesirable constituents.

The Specific Fuel Consumption of an engine is defined as the amount of energy produced per given amount of fuel consumed in the combustion process. The amount of fuel is quoted in grams or kilograms and the amount of energy produced in Kilo-Watt-Hours or Horsepower per hour.

Internal combustion engines can consume as little as 300 grams per kWh or as much as 1,200 grams per kWh.

In general the Specific Fuel Consumption is at its greatest (least efficient) when the engine is subjected to low loads, such as idle. This is because the ratio between the idling losses (due to friction, leaks, and poor fuel distribution) and the brake horsepower is the most unfavorable.

Most engines have the lowest Specific Fuel Consumption at three-quarter load, which is at 75% of the maximum power output and at about 2,000 RPM.

The Specific Fuel Consumption of engine is for the most part dependent on the mixture ratio of the Air/Fuel mixture. Consumption is at its lowest with an Air/Fuel Ratio of approximately 15 pounds of Air to one pound of Fuel. This means that 10,000 gallons of Air are needed to burn one gallon of Gasoline.

The mechanical design of the internal combustion engine has not changed since its conception in 1876, mainly because it works. The problem is, that it has been invented long before there was thorough understanding of thermodynamics or of the chemical reactions during combustion process. Further cheap and plentiful fuel -- Gasoline was easily available and until few years ago there was no concern with conservation or pollution.

As a result the internal combustion engine is an energy efficiency dinosaur that refuses to die.

To give you some idea why that is so, let’s consider this:

Gasoline contains about 42 to 43.5 Mega-Joules of energy in one Kilogram that is equal to about 18,060 to 18,705 Btu per pound.

The pie chart on next page will show you where all that energy that is available in Gasoline goes:

It may amaze you to know that only a quarter of the energy that is available in the Gasoline is converted into useful kinetic energy at the crankshaft. The rest or 75% is dissipated into the environment mostly as Heat.

With millions of motor vehicles in operation at any given moment on the Earth, just imagine what that does for "Global Warming"!

The 30% of the energy that is available in the Gasoline is used to Heat up the ambient Air, either directly, as is the case with Air-Cooled Engines, or indirectly as is the case with Liquid or Water Cooled Engines.

The reason why this waste is necessary is because the internal combustion engine is a Heat Engine, that is, Heat is produced by it. If the Heat can not be removed as quickly as it is produced the materials (Metals and Plastics) from which the engine is made would literally melt.

On highly efficient engine designs the losses through cooling system may be reduced to as low as 20%. This is achieved through the use of much more expensive materials that can be safely operated at higher temperatures without damage. The disadvantage of such designs is their high cost as compared to conventional designs and also the higher operating temperature causes the lubricant to deteriorate much more rapidly.

For every increase of 8° C to 10° C (12° F to 18° F) the oxidation rate of lubricant doubles and therefore the life of lubricant is cut in half. As a result motor oil must be changed twice as often, or else much more expensive synthetic lubricant must be used.

Just as is the case with Cooling, another 30% of energy is lost as Heat in the Exhaust gases. This is another area of great waste.

In some more racy engine designs as much as 35% of energy is lost in the exhaust and it is quite often enough to make the exhaust pipes glow red hot under full power output.

Some of this energy can be recovered with the use of exhaust driven turbo, output of which is usually used to drive another turbine that is used to supercharge the intake Air/Fuel mix

There is no reason, other than cost of the equipment, why this waste heat energy could not be used to drive electric generators, air conditioner compressors or other accessories either directly or through the use of mini "Steam Engines". However no manufacturer has yet designed any vehicle or engine system that fully utilizes all this Exhaust energy.

Pumping Losses amount to 5% of the energy that is available in the Gasoline. They comprise of the power that is used to suck the Air/Fuel mix into the engine, the power that is used to Compress the Air/Fuel mix, the power that is used to circulate the coolant and the power that is used to pump the motor oil in the engine.

Not much can be done about Pumping Losses, they are all important to the engine operation. The power that is used to circulate engine coolant can be eliminated by changing the engine design from Water Cooled to Air-Cooled.

Some of the Oil Pump Pumping Loss can be reduced by the use of lower viscosity lubricants and especially with the use of lubricants with high Viscosity Index.

Friction Losses in the engine account for 10% to as much as 15% of the energy that is available in Gasoline. In really inefficient engine designs the Mechanical Friction Losses can be as much as 20%.

The relationship of different lubrication regimes can be expressed graphically and it is called the
"Stribeck Curve". The graph below shows the relationship between the Friction Coefficient and Sliding Speed. However Oil Viscosity and Load also have an effect and can be expressed by formula:

Solid Contact is a stationary condition where there is intimate contact between two surfaces. They are interlocked by the surface roughness on each. The Friction Coefficient is at its maximum. The value of this condition is expressed as Static Coefficient of Friction. It is also called "Stiction", because the two surfaces literally stick to each other. The higher is the Static Coefficient of Friction or Stiction the more force it requires to move the two surfaces in relation to each other. Because there is no movement, there is no Wear. Because the two surfaces are stationary and interlocked by the surface roughness there is no Separation between the two surfaces.

 

 

 

 

 

Boundary Lubrication

· Velocity LOW

· Friction HIGH

· Wear HIGH

· Separation Less than Surface Roughness

Boundary Lubrication occurs when there is slow movement and when the two bearing surfaces are no longer interlocked but also not completely separated. The peaks of the surface roughness hit each other and as a consequence high Friction and high Wear results. Such lubrication condition exists during start-up.

Mixed Lubrication occurs when lubricant film is so thin or load so high that the lubricant can not completely separate the two bearing surfaces. Some minimal surface roughness contact occurs and this causes low Wear. As the Separation distance between the two bearing surfaces increases the Friction Coefficient rapidly decreases.

Hydrodynamic Lubrication occurs when the bearing surfaces are completely separated by an oil film that is thicker than the surface roughness. Under such condition the Friction is low and is affected only by the Viscosity of the Oil. Because there is no contact between the bearing surfaces there is no Wear. As the sliding velocity is increasing the Oil Viscosity causes slight increase in the Coefficient of Friction

.

Now that you understand the terms and functions of conventional liquid oil lubrication, you are ready for advanced lesson in Tribology – Sol Lubrication.

Sol Lubrication occurs when the bearing surfaces are completely separated by an oil film that contains colloidal particles which are larger in diameter than the surface roughness. Under such condition the Friction is low and is affected only by the Viscosity of the Sol. Because there is no contact between the bearing surfaces there is no Wear. As the sliding velocity is increasing the Sol Viscosity causes slight increase in the Coefficient of Friction.

On an overall basis, friction uses up, or wastes, a substantial amount of the energy generated by mankind, while a large amount of productive capacity is devoted to replacing objects made useless by wear.

Correspondingly, the potential savings offered by improved tribological knowledge are also great.

Unfortunately, the background of most engineers and designers in this important area is seriously deficient.

The average mechanical engineer has had less than two hours of instruction on wear as part of his university study.

While few engineers and designers understand the "Stribeck Curve" the knowledge and understanding of
Sol Lubrication is very rare.

The Friction that results from contact between the Cylinder bore and Pistons with Piston Rings accounts for 61% of Mechanical Frictional Losses or about 6.1% of the total energy in Gasoline.

Obviously this is very significant, not only because lot of energy is consumed, but because high Wear rate also results.

Because Boundary Lubrication condition exists at the ends of stroke, some metal-to-metal contact results and this causes excessive Wear of Cylinder at the ring contact area at TDC (Top-Dead-Center).

Additionally the Graphite Colloids protect the Cylinder and Piston from seizure and surface damage during high temperature and high load operating conditions.

SynLube™ also improves the quality of sealing so that Final Compression Pressure is increased and blow-by gasses are reduced.

All of the above factors contribute to significantly reduced Wear and to the Energy Efficiency for which SynLube™ Synthetic Super Lubricants are famous.

The Main Bearings and Con Rod Bearings together account for 31% of the Mechanical Frictional Losses or for about for 3.1% of the energy use that is available from Gasoline.

Because all these bearings are Plain Bearings they are subject to Sliding Friction and therefore a high Wear during start-up.

In a well-designed engine these bearings operate under Hydrodynamic Lubrication practically all of the time, except when engine is being started or when oil flow is interrupted.

Although the start-up condition accounts for only few seconds, it results in 75% to 90% of the bearing Wear.

In typical engine Valve Train accounts for about 8% of Mechanical Losses or about .8% of the energy consumption. Not all loses in the Valve Train are however frictional. this is because Valve Springs absorb some of the energy as they are being compressed during the engine operation.

Typical Valve Train requires about 60 lbf/s of torque to turn, this in turn is about 1/10 horsepower consumed at 6,000 RPM. Our research shows that use of SynLube™ reduces the torque required to turn the same valve train to about 3/4 of the original value. This in turn requires .025 less horsepower at 6,000 RPM. Although the fuel saving associated with this torque reduction is only .02 MPG, over the life of the vehicle it adds up to fuel saving of $162. However much more significant may be the increase in the service life of valve train drive components, such as gears, timing chains or timing belts.

Proof:

On LANCIA/FIAT 1.5 Liter L4 test engines a typical timing belt lasts 68,000 to 80,000 miles before failure, that is why the manufacturer recommends replacement every 52,500 miles.

The test was conducted from 1986 to 1991 by M.I.K. AUTOMOTIVE, INC. in North Hollywood, California on 1985, 1986 and 1987 model year BERTONE X1/9 automobiles.

One thing that you may not realize when you are buying Gasoline or Diesel Fuel is that you are getting a different amount of fuel each time when you are buying it!

You may think that the Gallon meters on pumps in the USA or Liter meters on pumps in Canada are accurate, and you will be correct.

After all you are charged the posted price, so how is it possible that you are not getting the same amount of fuel each time you buy it?

The answer is simple -- temperature!

What has temperature to do with fuel?

It causes it to expend when heated and to contract when cooled, and not just by a bit but by a quite a lot!

You may know that most substances and especially fluids expand when heated, when you put one quart of water into a calibrated glass column and heat it there will be more than one quart when hot. The specification that makes cold and hot water the same is its weight. One pound of cold water will still weigh one pound when hot.

The same applies to liquid fuel such as Gasoline and Diesel Fuel, except that it expands much more rapidly than water.

The scientific specification for the expression of how sensitive is a substance's expansion to its temperature is called the Cubic Thermal Expansion Coefficient. It is defined as the increase in unit volume of a body for a rise in temperature of 1°C (1.8°F).

The symbol used to identify Cubic Thermal Expansion Coefficient is lower case Greek letter Gamma = g

Vo = Volume at 0° C

In a table below are listed Coefficients of Cubic Expansion for some common substances that are of interest:

Interesting you may think, but unless you are a math wizard or a scientist the above table may have little meaning to you, so let's explain it by in common language and by an example.

Most likely you are familiar with a Mercury Thermometer. Chemists, meteorologists, and doctors have used such instrument for centuries.

It is mercury filled glass bulb connected to small glass tube to which a calibrated scale is attached. As temperature rises, the mercury expands and the silver colored mercury can be seen to climb up in the tube and thus indicating on the calibrated scale the temperature to which the bulb is exposed.

If you refer back to the previous table you will notice that Mercury has exactly the same Cubic Expansion Coefficient as Water that is g = .00018 for both of them.

What does this mean?

Well, if you pour a gallon of Water or a Mercury into a calibrated column at 0° C (32° F) and then heat it to 100° C (212° F), the fluid will expand and you will have more of it. How much more?

It is easy to figure out with the Cubic Expansion Formula:

Therefore you will gain 2.3 Fluid Ounces in Volume by heating the fluid by 100° C (212° F), however the Weight of the fluid will be the same, because you still have the same amount of it.

Although the Expansion in this example is 1.8% per 100° C (212° F), it is not very significant if you are dealing with an inexpensive fluid like Water, but it is very significant if you are selling expensive fluid like Mercury. That is why nobody will sell you Mercury by Volume, and why it is always sold by Weight.

The Expansion Coefficient for Petroleum and Gasoline is g = .001, for either of them.
That is more than five times greater when compared to Water or Mercury.

Statistically the difference between the overnight low and the daytime high temperature is about 11° C to 17° C (20° F to 30° F). Although the fuel is stored in under ground tanks, they are just few feet under the gas station's driveway, which is from black asphalt or dark concrete. If this surface is exposed to direct sun rays during summer the underground fuel temperature can be much hotter than the ambient air temperature. On the other hand, at about 4 AM when the ground temperature is at its lowest point, likewise the underground fuel temperature will be lowest.

From the above discussion it should be obvious by now that if you buy fuel on a hot and sunny summer day you will get lot less fuel (by Weight) in a Gallon than when you are buying it during cold winter before sunrise.
Even on the same day, when temperature can vary by as much as 30° F (17° C), it will make a difference.
How much of a difference? Let’s use our Formula again:

What this means is that if you buy 10 Gallons of fuel in the morning you get the same amount of fuel as when you buy 10.17 Gallons during afternoon. You can save 1.7% on your fuel costs just by getting into a habit of buying your gasoline early in the morning, instead of in the afternoon.