Effect of Gasoline Fuel Additives on Combustion and Engine Performance

Figure 2.1: Change in coefficient of friction with a friction modifier for different materials [95] 
Type of additive used depends highly on the surfaces it is meant to protect. 
Bowden and Tabor [95] describe experiments with lubricating oil and chemically 
surface active FM additives. Lauric acid interactions with different material surfaces 
were investigated. Results are reproduced in Figure 2.1. Silver, Chromium, Platinum 
and Nickel, which were expected to not react or only show little reaction with the acid, 
show only minor occurrence of interactions whilst copper, cadmium, zinc and 
magnesium displayed far greater reductions in the coefficient of friction. 
Representative chemical groups in additive composition include fatty acids, 
amines and other ashless long chain polar compounds [4, 18, 96, 97]. Treat rates 
typically fall below 1,000 ppm range. 
2.1.6
 
Carrier Fluids 
Carrier fluids (CFs) are used in conjunction with other additives. CF are also 
known as solubilising agents and are used to mix fuel insoluble additives into 
hydrocarbon fuels. Need for CF is determined by the chemistry and not the 
functionality of the additive and as such are mixed with different type of additives. 
Abramo et al. [98] describe a polyalkenyl succinimides based DCA mixed with a CF 
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Co
ef
ficient
 o
f 
F
rict
io
n, 
µ
Paraffin Oil
Parrafin Oil + 1% Lauric Acid

---

2.1 Fuel Additive Review 
40 
consisting mineral or synthetic oil, polyether, ester and a polymer or copolymer of an 
olefin hydrocarbon. McLean [99] suggests use of a CF containing mineral oil or 
synthetic oils such as polyesters or polyethers, or hydrocracked or hydroisomerised 
base stocks in concentrations of 30-60 % by additive compound weight (where total 
treat level of compound is 2,000 ppm) with a n-butylamine oleate based FM. A further 
use of CF has been described by Palmer and Heikoff [100] where piperidine is used 
as CF to make a protective coating containing methacrylic or acrylic/methacrylic 
polymer for nuclear fuel rod soluble in water. 
Published research on CFs is limited and most information available comes 
from development of other types of additives. However, according to Barnes et al. [4] 
typical CF include polyalphaolefins, polyethers, mineral oils and esters.