This method is the easiest but requires anhydrous ethanol, because methanol has limited solubility. A maximum of 10% diesel can be sub­stituted due to the lower solubility of methanol in diesel. No component changes; only adjustments of injection timing and fuel volume delivery are required to restore full power. Dodecanol is an effective surfactant for methanol-diesel fuel blends. Straight-run gasoline is an economical additive for ethanol-diesel blends.

Solubility of alcohols in diesel fuels is a function of (a) fuel tempera­ture, (b) alcohol content, (c) water content, (d) specific gravity of diesel, (e) wax content, and (f) hydrocarbon composition. Methanol solubility in diesel increases as the aromatic content goes up.

7.7.1 Alcohol-diesel fuel emulsions

Here, an emulsifier extends the water tolerance of alcohol-diesel blends. In general, equal volumes of alcohols and emulsifiers are required for suitable emulsions. No component changes, but injection volume and timing are adjusted for diesel fuel with alcohol then solutions, i. e., up to 35% diesel substitution is possible. Addition of ignition improvers, e. g., cyclohexanol nitrate, up to 1% helps increase the alcohol percentage up to 35% while maintaining a cetane rating at permissible levels. Cost of emulsifiers and poor low-temperature physical properties of emulsions limit the use of this technique. Stable emulsion requires the use of costly surfactants. Using higher-order alcohols improves the stability of blends at temperatures as low as —20oC.