From The Collaborative International Dictionary of English v.0.48 [gcide]:
Petrol \Pe*trol"\ (p[-e]*tr[=o]l), n.
1. Petroleum. [Archaic and R.]
[1913 Webster]
2. (p[e^]"tr[add]l"), Same as gasoline; -- British usage.
[British]
[PJC]
From WordNet (r) 3.0 (2006) [wn]:
petrol
n 1: a volatile flammable mixture of hydrocarbons (hexane and
heptane and octane etc.) derived from petroleum; used
mainly as a fuel in internal-combustion engines [syn:
gasoline, gasolene, gas, petrol]