Vapours (French accent engaged)
Didn’t we get something silly like 400 miles out of a brimmed to drained tank?
Oh and I’ve already forgotten to get that trip mode you showed me on the NAV.
I baulked at 420 in mine as i didnt want the fuel pump scrabbling round for dregs. It took 82 liters to brim fill again so in theory there was still around 6 liters in the tank.
The opposite end of the scale is the lowest i have had with mostly town and spirited driving is 300 miles to a tank. Which is still 15.5 mpg.
I really dont think 15 to 22 mpg range for a v8 with a 4.25 ltr displacement from the 2003 to 2007 ish time period was either low or much different to anything else of the same or similar displacement and cylinders. The M3 of the same time period had 1ltr less displacement.
Xk8 of the same era shows 16/18/23 mpg for the urban / combined / extra urban tests which is probably the closest comparison being a V8 and 4 liter displacement. Odly enough almost the same official mpg figures as the 4200.
Final gearing of the compared cars would effect the figures as would tyres , overall weight and many other factors. Where the rev limiter is has no bearing unless your driving on the limiter. Even then its going to reduce fuel economy as your pushing more fuel through at higher revs. We can do 70mph in any gear between 3rd and 6th. We put it in 5th or 6th to get better fuel economy by reducing the revs.
Running at lower revs is more economical on any engine. Its why diesels are much more economical for comparative displacements.
The wankel engine in an Mazda Rx8 is a 1.3ltr displacement in a small light car. Rev limiter 9000 rpm but still only get around 20mpg. Take the 1.3ltr diesel punto rev limiter around 4k and your looking around 65 mpg.
Two totally different engine and rev ranges but they do have one thing in common. The lower the revs the more mpg you will get at any given speed.
The 4200 and GS produced average mpg for the same / similar sized v8 engines of the day in a similar size / weight of vehicle.
If you took the cars out of the equation and just had the various 4 ish ltr v8 engines of the day on a test rig with the same gearbox and axle set up but no car then i suspect the mpg figures would be very similar for all the different v8 engines tested.