Chapter 28 Gasoline, Diesel, and Other Fuels

Chapter 28 Gasoline, Diesel, and Other Fuels Chapter 28 Gasoline, Diesel, and Other Fuels - Start

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Chapter 28 Gasoline, Diesel, and Other Fuels

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Presentations text content in Chapter 28 Gasoline, Diesel, and Other Fuels


Chapter 28

Gasoline, Diesel, and Other Fuels


Crude Oil

A fossil fuel

Varies in appearance

Composition varies, but is typically:

84% carbon

14% hydrogen

1 – 3% sulfurs

Less than 1% nitrogen, oxygen, metals, and salts


Lubricating oil




Diesel fuelGasolineNatural gas

Petroleum Products



The number of carbon atoms in HC molecule chain defines its length

When combined with the number of hydrogen atoms is called a chain

The shortest hydrocarbon is methane, CH

4, which is a very light gas



42 Gallon Barrel of Crude Oil Produces



Separates the hydrocarbons into useful substances

Very few of the fractions are usable without treating and cleaning

Some fractions are altered to be used for a specific application


Chemical Processing

Some fractions are processed to break down long chains into shorter chains

This process is called cracking

Hydrocarbon structure can be rearranged:

Often used to make octane boosters




Fossil fuels used for many purposes due to high energy density

Even though abundant, usage still increasing

Burning HCs releases CO


Increased CO2 in the atmosphere has been linked to global warming


A mixture of about 300 ingredients

Chemically represented as C8H15

Oil refiners must meet standards set by the American Society for Testing and Standards, the EPA, and some state requirements

Major factors affecting fuel performance:

Antiknock quality, volatility, sulfur content, and deposit control



Antiknock Quality

Represented by the octane number

Two methods used to determine octane number:

Motor octane number (MON)

Research octane number (RON)A test sample of fuel is used in a laboratory engine


Antiknock Index

Average of RON and MON (R+M/2)

Displayed on fuel pump

Most engines operate on regular gasoline

Higher octane fuel burns slower than low-octane fuel


Factors That Affect

Engine Knock

Fuel mixture

Over advanced ignition timing

Compression ratio

Valve timingTurbocharging or supercharging

Coolant temperature

Excessive carbon deposits

Air inlet temperature

Combustion chamber shape

Octane number



Readily evaporates so gas vapor adequately mixes with air for combustion

Gasoline volatility affects:

Cold starting and warm-up

High altitude operationCrankcase oil dilution


Volatility (Cont.)

Gasoline is blended for summer use and winter use

Fuels in high altitude areas must have higher volatility

Volatility most commonly measured by the Reid vapor pressure test


Water forms when hydrogen in the HCs are burned

Water leaves engine as steam but condenses back into water

When sulfur in the fuel burns it combines with O


to form sulfur dioxideSO2

can combine with water to form sulfuric acidSulfur Content


Anti-icing or deicer

Metal deactivators and rust inhibitors

Gum or oxidation inhibitors


Basic Gasoline Additives






Aromatic hydrocarbonsBasic Gasoline Additives (Cont.)



Reid Vapor PressureMeasures the volatility of the fuel

Affects how an engine runs in cold weather

Alcohol Test

Excessive alcohol can cause corrosion and damage to rubber components

May cause driveability complaints

Gasoline Quality Testing


Knowledge Check

What are three additives used in gasoline?


Renewable fuels are derived from non-fossil sources

Biomass fuels can be used in internal combustion engines and tend to be carbon-neutral

Ethanol and methanol fuels, such as E85

Already used as oxygenates in gasoline

Alternative Fuels



High quality, low cost, high octane fuel

Burns cleaner than gasoline

Produced from corn, sugar cane, grains, and other biomass waste

Commonly used in E10 and E85 blendsMost vehicles can use E10


Ethanol (Cont.)

Produced in the U.S. and can reduce reliance on foreign oil

Few vehicle modifications needed

Cleaner emissions than gasoline

Helps keep fuel system cleanCan absorb moisture, which can separate in fuel tank

Weak infrastructureHas a negative energy balanceE85 contains about 25% less energy by volume than gasoline



A clean burning alcohol fuel

Often made from natural gas but can be made from coal and biomass

Used in blends of M15 and M85

Blending with gasoline improves cold weather starting ability


Propane (LP-gas)

Liquefied petroleum gas is used by many fleets

Stored as a liquid

Produces less HC, CO

2, and COSlight engine power reduction from reduced cylinder filling


Compressed Natural Gas (CNG)

and Liquefied Natural Gas (LNG)

Abundant and less expensive than gasoline

Clean burning with 25% less CO


emittedStored at 2400, 3000, or 3600 psiRequires large storage tanksLNG requires less space but must be stored and dispensed at very low temperatures


CNG Storage


P-Series Fuel

Blend of natural gas liquids, ethanol, and biomass-derived co-solvents

Each gallon of P-series fuel emits about 50% less CO


, 35% less HC, 15% less COCould be 96% domestically derived

More than 60% of content is renewable



Can be extracted from many sources

Currently has a negative energy balance

Liquefied hydrogen stored at -423°F (-253°C)

Hydrogen fuel engines typically produce less power

Very little infrastructure


Fuel Cell Electric Vehicles

FCEVs have electric motors

A fuel cell generates electricity for the motor and/or battery

May use hydrogen or other fuel as the energy source

Pure water and heat are the only emissions


Toyota FCV Concept



Flex Fuel Vehicles

Designed to run on something other than gasoline

Bi- or multiple-fuel vehicles can use more than one fuel

May have two separate fuel tanks

Operate on one fuel or the other




Flexible Fuel Vehicles (FFV)

Can use ethanol and/or gasoline or a mixture of the two

Stored in the same fuel tank

PCM determines fuel used by the HO

2S and fuel trim readings


Knowledge Check

Technician A says all gasoline-powered vehicles can use E85 fuel. Technician B says only flex-fuel vehicles can use E85. Who is correct?


Diesel Fuel

Has about 15% more energy than gasoline

Small, high speed diesel engines require high quality, high volatility fuel

Diesel volatility measured by a cetane rating

Two grades of diesel fuel, Number 1 and 2Number 2 is most popular and available



Diesel Fuel (Cont.)

Is a high sulfur content fuel

Diesel engines emit particulates, called soot

High combustion temperatures produce high NOx emissions

Diesel fuel prone to waxing or solidifying in cold weather


Ultra-Low Sulfur Diesel Fuel

Previous standard allowed up to 500 PPM

2007 standard is 15 PPM

Allows diesels to emit less NOx, soot, and other sulfur compounds


Bio Diesel

Fuels derived from renewable biological sources:

Animal fats

Recycled restaurant greases

Vegetable oilsCan be used directly or blended


Bio Diesel (Cont.)

Advantages include:

Reduce foreign oil dependence

Carbon neutral

Decreased HC emissions by 50%Nearly eliminates sulfur emissionsCO emissions decreased an average of 48%

PM emissions reduced by 47%Smoother, quieter, longer diesel engine life


Bio Diesel (Cont.)

Disadvantages include:

High production costs

Not readily available

Increases NOx emissionsCannot be used in vehicles built before 1992 without modifications to the fuel system


Diesel Engines

The fuel is ignited by the heat of compression

Higher compression results in more efficiency than a gasoline engine

Modern diesels quieter and more efficient than previous diesel engines


Modern Diesel Engine


Diesel Combustion

Combustion can take place in three steps


Engine Control Systems

All 2007 and newer light-duty (14,000 lb GVW) diesels are equipped with OBD II

Some unique monitors for diesels include

EGR cooler monitor

Oxidation catalyst efficiency monitor


Diesel Fuel Injection

Direct injection into combustion chamber

Many modern diesels use common rail injection


Injector Nozzles

Delivers the fuel to the cylinder

Nozzle tip atomizes the fuel

Fuel pressure and the time the injector is open determines the amount of fuel delivered


Electronic Unit Injection

Uses a camshaft-driven high-pressure fuel pump

PCM controls injector opening time

Did not have as precise control as needed to meet modern emission standards


Hydraulic Electronic Unit Injection

Uses engine oil pressure to control injector operation

Used until 2010

Proper maintenance is critical on HEUI systems


Common Rail Injection

A fuel rail carries high-pressure fuel to each injector

Each injector independently controlled by the PCM

Used in all 2010 and newer engines


Glow Plugs

Used to warm the air and combustion chamber area for cold starts


Solenoid Injectors

Used in common rail systems

The solenoid opens to allow fuel to flow to the injector nozzle

Controlled by the PCM


Piezoelectric Injectors

Have no moving parts

Contain thin layers of piezo material

When current flow through material, it expands, allowing fuel to flow through the injector


Fuel Delivery

A low-pressure transfer pump in the tank supplies fuel to the high-pressure pump

May contain a water separator

Injection pump may be timed to the engine



Used on nearly all diesel engines

Many newer engines use variable geometry turbochargers


Knowledge Check

Technician A says glow plugs are used to ignite the fuel in a diesel engine. Technician B says glow plugs warm the engine to allow easier starting in cold weather. Who is correct?


Diesel Emission Controls

Diesels emit carbon monoxide, hydrocarbons, carbon dioxide, particulate matter (soot), and oxides of nitrogen (NOx)


Diesel Oxidation Catalysts (DOC)

In use since 2007

Flow through catalysts similar to those used on gasoline engines

Converts fuel-rich gases into heat

Reduces CO, HC, and other compounds


Diesel Exhaust Particulate Filter

The DPF works with the DOC and EGR to reduce NOx

Over time, trapped particulate plugs the filter

The PCM will perform a cleaning or regeneration of the filter

Requires the use of low-ash oil to prevent ash loading of the filter


Exhaust Gas Recirculation (EGR)

Injects an amount of exhaust gas into combustion chambers

Reduces combustion temperatures and NOx emissions

An EGR cooler removes heat from the gas before it enters the engine



Selective Catalytic Reduction (SCR)

Fits between the DOC and DPF

Reduces NOx emissions

Uses a reductant or reducing agent

Requires refilling as part of normal maintenance


Positive Crankcase Ventilation (PCV)

Also called crankcase ventilation (CCV)

Removes crankcase gases


TDI Engines

Turbocharged Direct Injection

Made by Audi and VW

Use common rail and piezoelectric injectors

Variable geometry turbo



Most of the diagnostics is scan tool based

Smoke diagnosis

White smoke may be caused by a misfire, faulty glow plugs, low compression, poor injector operation, and coolant leaking into the cylinder

Grey or blue smoke is caused by oil burning in the cylinderBlack smoke indicates excessive fueling


Diagnostics (Cont.)

Remove the glow plugs to perform a compression test

Cylinder power balance testing performed with a scan tool

Glow plug resistances should be equal

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