RRC V8 vs Disco V8 fuel economy?

Beast o Bodmin said:

Hgf.

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tacr2man said:

engine temp is very important with efi engines as it changes how much fuelling as cooler requires more fueling , untill you get into high revs area where fuelling has to take into account cylinder temps so fuelling is increased to act as coolant thats how it was explained to me it works on V12 Jag in particular (by Jag factory tech) HTSH

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MikeV8SE said:

OK, this is not the most accurate comparison in the world, but bear with me!

My RRC 3.9 V8 auto, showing 90k on the clock, seems to be signifcantly less economical than my mates Disco 1 3.9 V8 auto (153k on the clock).

As a case in point, the other weekend 3 of us went greenlaning in my RRC, drove around 90-100 miles there and back, plus the greenlaning in between - used about 3/4 of a tank, or £60 in monetary terms.

This weekend 2 of us went to a pay & play day in his Disco, again around 90 miles there and back plus the offroading itself, and used just 1/2 a tank, around £40!

So, given the cars weigh similar amounts, cruised at around 60-65mph there & back and are both about as aerodynamic as my house, what's could cause mine to use 50% more fuel?? Oh, and tyre pressures on both were checked before we went to each day and were fine.

Since I've had the car I've changed the oil (Mobil 1 10W40), oil filter (genuine LR), air filter (K&N filter element) and coolant change + flush.

Conversely, since owning his Disco he changed the oil (Halfords 10W40) and oil filter (genuine LR) and tha's it.

So, what else could cause such a difference? The engine runs really sweet, but what else could I check/try? New spark plugs? Leads? Thermostat (it is a bit lazy, but surely once up to temperature shouldn't make a difference)??

Cheers!

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