Mercedes SLK — MPG & Fuel Costs 2025
Mercedes' popular compact roadster with a folding metal roof, combining boulevard comfort with sensible fuel costs.
The third-generation Mercedes SLK (later renamed SLC) is a premium two-seat roadster featuring a folding metal Vario-roof. It offered a more relaxed, comfortable drive than the sporty Porsche Boxster.
Crucially for UK buyers, this generation introduced a highly efficient 2.1-litre four-cylinder turbodiesel (SLK 250d), creating a unique combination of open-top driving and hatchback-like fuel costs.
Real-world economy for the diesel roadster is outstanding, returning up to 50 MPG on longer motorway runs. Petrol SLK 200 models average around 37 MPG.
TL;DR
37 MPG
Real-world petrol
48 MPG
Real-world diesel
60L
Tank capacity
£82.08
Full tank (petrol)
16.8p
Per mile (petrol)
Real-World Fuel Economy: The Mercedes SLK achieves an estimated 37 MPG (petrol) and 48 MPG (diesel) in real-world UK driving conditions, accounting for a 12% WLTP real-world penalty.
Forecourt Fuel Cost: Refueling the 60-litre tank completely costs approximately £82.08 (petrol) or £85.26 (diesel) at average UK fuel price rates.
Fuel economy at a glance
37
Real-world MPG
Petrol
43.5
Official WLTP
Petrol
48
Real-world MPG
Diesel
56.5
Official WLTP
Diesel
Annual fuel costs by mileage
| Annual mileage | Petrol | Diesel |
|---|---|---|
| 5,000 miles/yr | £840 | £673 |
| 7,400 miles/yr(UK average) | £1244 | £996 |
| 10,000 miles/yr | £1681 | £1346 |
| 15,000 miles/yr | £2521 | £2019 |
| 20,000 miles/yr | £3362 | £2692 |
| Full tank (60L) | £82.08 | £85.26 |
| Cost per mile | 16.8p | 13.5p |
Based on UK average fuel prices: petrol 136.8p/L · diesel 142.1p/L. Prices updated regularly.
How does the SLK compare?
Tips to get better MPG from your SLK
The SLK 250d diesel has immense torque; cruise at low RPM in top gear.
Maintain folding roof seals to prevent water ingress and wind noise drag.
Avoid carrying heavy items in the boot, which is already restricted when the roof is folded.
Is the cheaper petrol station worth it?
In a Mercedes SLK achieving ~37 MPG real-world, if you fill 48 litres and the alternative station is 10p/litre cheaper:
£4.80
Gross saving on fuel
£0.50
Cost of 3-mile detour
£4.30
Net saving ✓
You could drive up to 29 miles round-trip before the saving disappears entirely.
Calculate for your exact situationPopular variants
Frequently asked questions
What is the real-world MPG of the Mercedes SLK?
The Mercedes SLK achieves approximately 37 MPG in real-world petrol driving — around 12% lower than the official WLTP figure of 43.5 MPG due to real driving conditions. Diesel variants achieve around 48 MPG real-world.
How much does it cost to fill a Mercedes SLK?
The Mercedes SLK has a fuel tank of 60 litres. At the UK average of 136.8p/litre for petrol, a full tank costs approximately £82.08. Diesel costs approximately £85.26 for a full tank.
What is the annual fuel cost for a Mercedes SLK?
At the UK average annual mileage of 7,400 miles and current petrol price of 136.8p/litre, a Mercedes SLK costs approximately £1244 per year in fuel. At 10,000 miles/year the cost rises to £1681. Actual costs vary with your driving style and mileage.
Is it worth driving to a cheaper petrol station in a Mercedes SLK?
In a Mercedes SLK doing ~37 MPG real-world, driving 3 miles round-trip to save 10p/litre on a 48-litre fill nets approximately £4.30 after the extra fuel cost. You could drive up to 29 miles before the saving is eaten up. Use the WorthThePump calculator for your exact situation.
How much does the Mercedes SLK cost per mile in fuel?
The Mercedes SLK costs approximately 16.8p per mile in petrol at current UK prices. Over a typical commute of 30 miles per day, that is approximately £5.04 per day in fuel.
What is the WLTP MPG figure for the Mercedes SLK?
The official WLTP fuel economy figure for the Mercedes SLK is 43.5 MPG. However, real-world MPG is typically 10–15% lower than WLTP due to cold starts, air conditioning, motorway speeds, and varying loads. WorthThePump uses a 12% real-world penalty to give a more accurate estimate.
Related guides
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