Which car has the greatest range?

Had a Cayenne 958 diesel a few years back. Had a 100litre tank. After a refill it regularly showed a 900 mile range. Reality - would do about 750 miles if I just did motorway miles.

Took bloomin ages to fill up though and you certainly couldn't use the £99 max fill type pumps that were around then...

That's our V70 D5 after a return trip from Yorkshire to Somerset, with a bit of running around whilst we were down there. 518.9 miles complete and 335 remain, and it was showing 1000 mile range after about 50 miles into the journey but realistically 800+ should be easily achievable.
There are more economical engine options, like the 1.6 diesel which would be dreadfully underpowered but with a 70 litre tank should go for miles without a refill.

There must come a point where lugging around huge quantities of fuel in terms of weight becomes a hindering factor in terms of the range the extra fuel costs. I wonder what the calculations for that look like and at which point it happens.

Must admit I’m highly impressed with some of the mpg and ranges quoted here. It’s pretty impressive when a bmw 3 series is managing near enough 70-80mpg as some are saying they get. It really does show how far we have developed the efficiency of ICE cars over the last few decade. I remember when 30mpg was nearly unheard of from a petrol.

My 3L M135i will easily return mid 30s on the motorway without trying. If you drive Uber careful I’ve had 42mpg once (long stretch of M1 being converted to smart at the time so sat at 50mph for mile after mile helped.

I used to do a 440 mile round trip every week, doing it in the M5 was pain as I'd have to fill up even when setting off with a full tank doing it in the 730d I'd make it on half a tank easily.

Fuel doesn't weigh that much in the context of a car (petrol is less dense than diesel, but both are less dense than water, but 100litres of diesel only weighs (has a mass of, if we are being accurate) 85kg, so same as a single passenger more or less ) and weight/mass doesn't have a big impact on fuel economy, especially assuming these long distances are being covered at a steady speed so I think you'd need a vast amount of fuel for it to make an impact. The extra weight may even lower the car improving aerodynamics.... The cannonball guys fit very large fuel tanks, one covered the whole of the 'states at very high speeds with just one refuel and that was still faster than stopping more often. He basically took the car up to it's max gross weight with fuel, after removing rear seats/trim etc and it was still the best way to do it.

Scania R450 will do 1000 miles to a tank

Weight isn't a factor in consumption when you're at a steady cruise.

Only really comes into play when you're accelerating. An extra 20 or 30kg on a 2t car wouldn't even be measurable IMO.

I've had both a S60 D5 (proper D5 with 5 cylinders ) and V60 1.6d.

I got the same real world MPG from the 1.6 as the 2.4 as you always drove the smaller engine with your foot to the floor.

I'm sure it was more economical on a motorway cruise, but with the big range there would always be plenty of town driving on every tank.

If only my Skoda Octavia had a decently sized fuel tank. If it had the same size tank as my old Passat I'd see 1000 miles between fills but as it is it's only 550miles or so. My transporter van isn't bad, 800 miles between fills when driven carefully.

I've got a Honda civic tourer 1.6dtec. I think official figures are about 70mpg ish.

We did 1300 miles recently on a week away. I do have the figures somewhere but the end result was calculated 81mpg give or take 1/2/ either way

Again recently did a trip to Wales which was 280 mile round trip with 180 miles on b roads and calculated to 70mpg.

It has a 50L fuel tank capacity apparently which is food for thought as when I think it's empty I can only usually get just under 40L in it.