Diesel vs Petrol Fuel Economy Explained
If you are comparing diesel vs petrol fuel economy or asking whether diesel is more efficient than petrol, split the question:
1. Litres per 100 km (energy efficiency)
2. Dollars per 100 km (wallet efficiency)
Why brochure figures mislead
Definition
- Wallet efficiency
- Dollars per hundred kilometres combines real litres per hundred with the actual diesel or unleaded price you pay, not the label that sounds cheapest.
Litres per hundred km lens
- Highway towing can favour modern diesel thermodynamics
- Urban creep hurts both fuels differently by tune
Dollars per hundred km lens
- Diesel can cost more per litre even when litres drop
- Premium-required petrol shifts the economics again
Key points
- Reset a trip, refill, divide litres by distance—repeat twice.
- Compare fuels on the same day using the directory.
- Use the calculator for annual scenarios you will actually drive.
Pros
- A simple log beats arguing about brochure winners.
Cons
- One short tank on holiday traffic misleads for a year of commuting.
Australian lab figures help rank cars, but your commute dominates outcomes: traffic, tyres, roof racks, and cold starts all move litres.
How to measure real L/100 km
- Reset trip on a full tank, refill, divide litres by distance.
- Repeat across two tanks for stability.
When diesel wins on litres
Steady highway towing and long runs often favour modern diesel thermodynamics.
When petrol wins on dollars
If diesel is priced high on the board and your annual kilometres are modest, ULP 91 can win on dollars per year even when diesel wins on litres.
Use live prices: directory. Then run diesel vs petrol calculator.