Neat alcohols are used in diesel engines by increasing the cetane number sufficiently using ignition improvers. This technique saves the expense and complexity of engine component changes but adds the cost of igni­tion improvers. The cost of 10-20% ignition improvers is quite prohibitive.

The most effective ignition improvers are nitrogen-based compounds which can aggravate exhaust emissions of NOx. Ethylene glycol nitrates have shown promising trends at 5% concentration.

Engines operating on cetane-enhanced alcohol need a few changes, e. g.,

■ Injection volume and timing must be adjusted to obtain optimum performance.

■ A large pump, fuel lines, and injectors are required to satisfy total fuel requirements of the engine for the desired output.

■ A lubricant (generally castor oil used so far) is required to be added to alcohols using improvers.