Effect of Gasoline Fuel Additives on Combustion and Engine Performance

Standard 
Date 
CO 
HC 
HC+NOx 
NOx 
PM 
PN 
Euro 1 
1992 
2.72 
- 
0.97 
- 
- 
- 
Euro 2 
1996 
2.20 
- 
0.5 
- 
- 
- 
Euro 3 
2000 
2.30 
0.2 
- 
0.15 
- 
- 
Euro 4 
2005 
1.0 
0.1 
- 
0.08 
- 
- 
Euro 5 
2009 
1.0 
0.1 
- 
0.06 
0.005 
6.0x10
11
Euro 6 
2014 
1.0 
0.1 
- 
0.06 
0.005 
6.0x10
11
Table 1.1: Regulated exhaust gas emissions within the EU for gasoline powered passenger 
cars. A given standard applies to all new cars sold within the EU after a given date. PM and 
PN emissions are only applicable to engines with direct injection. All emissions are 
measured in g/km, except for PN which is measured in #/km [3] 
1.1
 
Background on Additives 
Fuel additives are chemicals used in very small quantities to enhance or add 
properties to base fuels. The quantity of additive added to base fuels is referred to as 
a treat rate and is typically in the range of 1-20,000 mg/l. According to Barnes et al. 
[4], improving engine efficiency and emissions through the use of fuel additives has 
been practiced for nearly a century. The earliest additives were lead based 
organometallic compounds that reduced auto-ignition in spark ignited combustion 
systems but concerns with pollution and legislation changes mean in the developed 
world only organic compounds are now employed. Since the early days, additives that 
function also in areas outside the combustion chamber have been developed. Along 
with aiding combustion reactions and pathways, additives are utilised to address issues 

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1.2 Objectives 
21 
arising from deterioration or failure of fuel delivery system components due to wear 
or accumulation of deposits. For optimum operation, this is especially important in 
modern fuel metering systems, where high pressure direct injection systems and 
electronic control and monitoring mechanisms are sensitive to deviations from normal 
operational characteristics. Additives additionally provide benefits in refineries, where 
lower-refined fuels can be made to offer similar if not better physical and chemical 
properties compared to their highly refined derivatives. 
Typically, additives are supplied to oil companies as pre-prepared packages 
tailored to customers’ specifications and often are only mixed with the fuel at the final 
stages of the supply chain which enables great cost savings and product differentiation. 
In general, irrespective of their function, additives are employed to affect the overall 
performance of internal combustion engines. Additive functional groups include 
combustion and lubricity improvers, detergents and carrier fluids and characteristic 
chemistries often comprise polymeric compounds with polar head groups and fuel 
soluble long chain tails. In some cases oxygenates that are added to fuel in quantities 
of up to 50% by volume are referred to as additives but in present work only the 
performance modifying compounds used in the parts per million (PPM) range are 
considered. A detailed overview of the different additive groups investigated in the 
present study will be given in Chapter 2.