System, a method of controlling a system, and a vehicle comprising a system

A single-fuel internal combustion engine system for a vehicle, comprising:

• an internal combustion engine, ICE, operable on a low cetane fuel, the low cetane fuel being any one of hydrogen, methanol, ammonia, E85, pure ethanol and naphtha, said internal combustion engine having a cylinder at least partly defining a combustion chamber and an ignition source for the low cetane fuel;
• a fuel injector for injecting the low cetane fuel into the combustion chamber;
• an ignition improver device in fluid communication with the fuel injector and further configured to supply an ignition improver fluid to the low cetane fuel;
• a control unit configured to selectively operate the ICE in a spark ignition, SI, mode and a compression ignition, CI, mode, wherein the control unit is further configured to determine an ICE operating condition and control the ignition improver device to supply a given amount of ignition improver fluid to the low cetane fuel on the basis of said determined ICE operating condition.