Just kidding... or am I? Anyways, being a Merchant Mariner is one of my more enjoyable diversions and I mostly work on gas-turbine tankers. They are much cleaner and very efficient, but are notoriously expensive. They don't make much profit with that kind of overhead. FYI, the Queen Elizabeth 2 is 70,327 tons, 963 feet long, 105 feet wide. It has 32 feet of draft. It has a 25 - 28.5 knots cruising speed (maximum 32.5 knots). Service speed is achievable using only 7 of the 9 engines.

There is a problem though with the 1 gal/6 inch fact. This is on the website:

Fuel Consumption:

18.05 tons per hour, or 433 tons per day.

This is equal to six of the ship's swimming pools.

The ship's fuel oil tank capacity of 4,381.4 tonnes is sufficient for 10 days' sailing at 32.5 knots, equalling 7,800 miles.

One gallon of fuel will move the ship 49.5 feet; with the previous steam turbine engines, one gallon of fuel moved the ship 36 feet.

This is probably because of the variation of fuel usage between starting from a stop or cruising at 25 kts.