1. converting an engine or vehicle to run on diesel fuel instead of petrol or another fuel
Usage: British English spelling; American English uses 'dieselizing'; present participle or gerund form of 'dieselise'
2. equipping or modifying a system, fleet, or infrastructure to use diesel fuel
Usage: often used in industrial or transportation contexts

Examples

• The company is dieselising its delivery trucks to reduce fuel costs.
• Many European cities are dieselising public transport fleets.
• Dieselising older vehicles can improve fuel efficiency.
• The government considered dieselising the railway network.
• Mechanics specialise in dieselising engines for better performance in heavy-duty applications.