For most Kenyan drivers, choosing between a petrol or diesel car comes down to more than just the price at the pump.

Fuel efficiency, maintenance costs, and even driving habits all play a role.

To make an informed choice, it helps to understand how each engine works and what that means for performance and running costs.

Petrol engines ignite a mixture of fuel and air using a spark plug. Diesel engines compress air until it becomes hot enough to ignite the fuel when it is injected.

This difference in ignition method allows diesel engines to extract more energy from each litre of fuel than petrol engines.

In Kenya, both types of engines power a wide range of vehicles from small hatchbacks to heavy-duty trucks.

From July 15 to August 14 2025, the retail price of super petrol in Nairobi is Sh186.31 per litre and diesel is Sh171.58 per litre.

Petrol cars in Kenya average about 12 kilometres per litre under everyday driving conditions.

Diesel models typically return around 15 kilometres per litre.

A driver covering 1,000 kilometres per month would use roughly 83 litres of petrol versus 67 litres of diesel.

Despite diesel’s lower price per litre, the higher efficiency is what creates real savings on long trips.

Diesel vehicles often cost 10 to 15 percent more to buy than petrol models.

The reason being that they require stronger engine parts to handle high-pressure operation and have additional exhaust filters.

Servicing a diesel car can cost 20 to 30 percent more than a petrol car because diesel filters and fuel injectors need regular cleaning or replacement.

In urban driving with frequent stops and short trips, diesel filters can clog more easily, increasing the cost and frequency of maintenance.

Diesel’s higher energy density and greater fuel efficiency produce about 10 percent less carbon dioxide per kilometre than petrol.

Burning one litre of petrol usually emits around 2.3 kilograms of carbon dioxide.

Burning one litre of diesel emits about 2.6 kilograms of carbon dioxide, but that litre will cover a longer distance.

On the other hand, diesel engines emit higher levels of nitrogen oxides and fine particles.

Diesel engines’ articulate filters capture most soot, but some fine particles and gases remain, which can affect air quality and health.

For mainly urban use and short trips in cities like Nairobi or Mombasa, petrol cars tend to be more practical.

They warm up quickly, avoid filter-clogging issues and cost less to maintain in stop-and-go traffic. Diesel cars perform best on long highway journeys or when carrying heavy loads.

Their stronger low-speed pull makes them ideal for towing or for drivers logging more than 20,000 kilometres per year.

In those cases, diesel savings on fuel can outweigh the higher upfront and servicing costs.

They should calculate fuel spend based on current pump prices and expected monthly distance.

Add estimated servicing costs and consider how often short trips may affect filter life.

Petrol offers lower upfront cost and simpler upkeep for most city drivers.

Diesel delivers better fuel economy and durability for high-mileage or heavy-duty needs.

A clear, fact-based comparison of these factors will guide drivers towards the right choice.