How much fuel does a cruise ship use?

A client asked me the other day how much fuel a cruise ship uses on an average voyage compared to his car. I wasn’t sure what to tell him as it wasn’t a question I’d ever been asked before but I went away and did some rough, (very rough), maths work to try and calculate it for him.

You can check out the results below, (the maths is very rough so feel free to correct me if you can).

The first problem I ran into is that cruise ships don’t use the same fuel as cars. They are powered by something called Marine Oil or bunker fuel as it is sometimes called. Bunker fuel is currently being sold for about £720 a tonne.
Most cruise ships can hold anything up to 1 million gallons of fuel so you can see straight off it’s going to cost a fortune to fill them up.
The average price for a litre of diesel to fill up your car, at least according to a quick Google search, is £1.33, (I don't drive so don't quote me on that).

The second problem I ran into is which cruise ship to base this on? Obviously different cruise ships are different sizes with different engines etc. I settled on Cunards Queen Mary 2 for two reasons
a) Because she’s an ocean liner and
b) I just really like that ship.

The QM2 has 4 diesel generators to push the ship along at an average speed of 25 knots with a maximum speed of 30 knots by using 2 gas turbine generators which burn 6 tonnes of marine gas oil per hour. Overall it has miles per gallon figure of 0.00753 or moves 40 foot per gallon of fuel burned, (thanks to another quick Google search).

So, assuming my maths work is right, (always a big assumption, I’m a travel agent, not a mathematician):
One tonne of marine oil will cost £720 whilst one tonne of car diesel will cost £1330.

The QM2, on that can do about 40 feet to the gallon whilst an average car could do about 55 to 60 miles to the gallon, (says the diesel driver sitting next to me).

The third problem then becomes passenger capacity. Even a people carrier can only fit a maximum of 7/8 people in it whilst the QM2 can hold 2058 people at maximum capacity. The fuel cost would obviously be shared amongst all the passengers so.......
£1330 divided by 8 is £166.25 a person
£720 divided bu 2058 is only £0.34p a person, which means
Assuming you can find 2058 people in the same are as you, traveling to the same place as you and you can figure out a way to make the QM2 road legal and find a route with no low bridges.......
Your daily commute to work is cheaper in the QM2!

Strange but true.