What to Fill Up and Where: Fuel in the Rental Fleet

--- slug: fuel-and-refuelling-in-czechia title: "Fuel and Refuelling in the Masons Fleet" description: "Three types of fuel in the rental fleet: petrol, diesel and electric. What to confirm before driving off, how fuel-level returns work, and what to avoid." h1: "What to Fill Up and Where: Fuel in the Rental Fleet" --- Across a fleet of 23 cars there are three different types of fuel, and what sets them apart isn't character but the sequence of actions you need to get right partway through a trip. A petrol car demands attention to the correct fuel grade, a diesel car demands that the grade never gets confused with something else, and an electric car demands that you plan your stops in advance. A mistake at this point costs more than any other slip-up in a rental.

In short. The car is returned with the same fuel level it was handed over with, and any shortfall is charged at the actual cost of refuelling. The required fuel grade is marked on the specific car's filler flap, not in the specifications on the site — you need to check it at pickup. For the electric car, the route is built around charging stops, because range isn't published on the listing.

Why the question comes up before you ever reach a filling station

At the filling station it's already too late. The question of "what to put in" is answered in two minutes at pickup, and it cannot be answered at all if those two minutes are skipped.

The reason is that a premium rental fleet isn't one car in three colours — it's a mixed fleet. On the same list you'll find turbocharged petrol cars, diesel SUVs with an electrical add-on to the onboard network, and an electric pickup. There's no universal rule of "fill up with the most expensive"; for a diesel engine, the most expensive pump at a filling station can be exactly the one after which the car ends up on a tow truck.

The second layer is financial, and it's also worth sorting out in advance. Fuel isn't included in the rental: the car is handed over at a given level and expected back at the same one. Any shortfall is charged at the actual cost of refuelling, with no service markup — but also with no rounding in the renter's favour. The practical takeaway: keep the receipt from your last fill-up until the car is returned.

The third layer is road costs beyond fuel itself. Fines, parking, motorway vignettes and toll sections incurred during the rental are the renter's responsibility. That's not about fuel directly, but it sits in the same column of the final reckoning at return.

There's also a fourth layer people tend to remember at the last moment — time. Refuelling a petrol or diesel car takes five minutes anywhere along the route; charging an electric car takes half an hour or more, depending on the station. If a trip is tightly scheduled, that extra time has to come out of somewhere — not the driving itself, but lunch, a walk, or the buffer before the drive back. So fuel type is worth treating as a scheduling parameter, not just a line in the specifications.

Three types of fuel across the fleet

Below is the whole fleet by fuel type and drivetrain, exactly as published on the listings. This is the bare minimum that shapes trip logistics — where to stop, and how often.

Two rows need explaining. Both the BMW X6 30d and the Mercedes-Benz A-Class carry a diesel index in their engine designation, while the fuel field on the listing says petrol. One of the two values is wrong, and there's no way to tell which one from the site alone. This is exactly the kind of case where you need to confirm the fuel type when booking and then double-check it at the filler flap before the first fill-up. The full list of cars is in the fleet section.

Petrol: the grade is set by the car, not by habit

Eighteen of the 23 cars in the fleet run on petrol, and almost all of their engine designations carry signs of forced induction — TwinTurbo, Biturbo, TFSI Turbo. Fuel requirements for engines like these are set by the manufacturer, and set individually: the minimum permitted and recommended octane rating is marked on the inside of the filler flap and in the car's owner's manual. These figures aren't published on the fleet listings.

From this comes a sequence of actions that works without exception. Check the filler flap at pickup. Remember it or photograph it. At the pump, cross-check the label on the nozzle against what's written on the filler flap. If the labelling at a particular filling station looks unfamiliar, ask the attendant rather than choosing by price.

The logic of "fill up with a higher grade than needed, it can't hurt" is safer than the reverse, but it isn't universal either: fuel with a higher octane rating doesn't by itself add power to an engine designed for a lower one, whereas fuel below the required grade can cause the electronics to limit output — precisely to protect the engine.

One detail worth flagging for anyone used to other markets: pump labelling varies from country to country in the region, and matching nozzle colours guarantees nothing. Go by the label, not the colour — a rule that saves stress at the first filling station on a cross-border trip.

Diesel: the main risk is picking the wrong pump

There are two confirmed diesel cars in the fleet, per their listings: the Mercedes-Benz S 350 d and the BMW X7 xDrive40d. The latter's listing additionally notes a 48-volt onboard network — this is an electrical add-on to the powertrain, not a second fuel type: the car is refuelled like an ordinary diesel and has no separate socket for charging.

Diesel carries one practical risk, but an expensive one. If petrol ends up in the tank, the engine must not be started: as long as the fuel hasn't reached the fuel system, the problem is limited to draining the tank; once the engine starts, it becomes a repair job. The procedure for this mistake is simple: don't turn the key, don't press the start button, call the rental company and wait for instructions. That's exactly what round-the-clock support is for; contact details are in the contact section.

Whether AdBlue needs topping up on a long rental, and who does it, isn't described on the site. For a short trip the question usually doesn't come up, but for a rental spanning several weeks it's worth asking in advance.

Electric: a different logic for stops

The Tesla Cybertruck is the only electric car in the fleet. Its stated top speed is 210 kilometres per hour, 0–100 acceleration is 4.1 seconds, and it has all-wheel drive. Range, battery capacity and supported charging power aren't stated on the listing, so this text deliberately gives no concrete figures for charging stops — instead, it gives a principle.

The principle is this: for an electric car, the route is planned in reverse order. First you pick the charging points along the way, then you fit the trip's schedule around them. For routes from Prague within about two hours — Plzeň, Karlovy Vary, Brno — the difference from an ordinary car is small. For a cross-border trip with two or three long stretches on the motorway, planning needs to be taken seriously.

The second point is pace. In an electric car, energy consumption rises with speed more noticeably than in a car with an internal combustion engine, and sustained motorway speeds of 130 kilometres per hour eat into range harder than driving on a lower-class road. For the Cybertruck this matters even more, since a pickup body doesn't help aerodynamics.

And the third point: the return condition for the electric car is stated on the site under the same "same level" logic. Exactly how a charge shortfall is calculated isn't described on the site — confirm when booking.

A separate note on cold weather. On frosty days, range in an electric car is shorter than in warm weather, and charging speed on a cold battery is lower — this is a general property of the technology, not a quirk of this particular model. For a winter trip to the Krkonoše mountains or toward the border, this means building in an extra time buffer on top of the usual one.

What not to do

Fill up by nozzle colour. Go by the label on the pump and the label on the filler flap.

Start the engine after a wrong fill-up. Before starting, it's a tank drain; after starting, it's a repair.

Assume that "premium car means premium fuel" settles the question. For diesel, the most expensive petrol pump is the worst possible choice at the filling station.

Return the car with a lower level than at pickup. The shortfall is recalculated at the actual cost of refuelling, and it's more noticeable than it looks against the rest of the trip's expenses.

Plan an electric trip around the driving time shown by the navigation app. Charging stop time isn't included in that figure.

Rely on the "fuel" field on a listing if the engine designation carries a different index. Two such inconsistencies already exist in the fleet; checking the filler flap takes ten seconds.

FAQ