fuel consumption p38 4.6

Saint.V8 · Nov 4, 2011

The On-Board Computer is not very accurate and can only be regarded for guidance.

The calculation is carried out by using the fuel tank sender and the total mileage completed since last reset...so if you are on a side slope (even a slight one) the fuel gauge sender gives incorrect information for that part of the journey, or if there are long up/down hill sections, again the information used would be incorrect....I estimate the error could be around the 10-15% or even up to the 20% mark in some cases.

Best to use the Brim to Brim method by filling up, do some miles, then fill up again and note the fuel quantity used.

My Previous V8 P38's were doing 14-16 around town and I managed to get 22 on a run once...but so very rare....

fortgrange · Nov 4, 2011

Saint.V8 said:
The On-Board Computer is not very accurate and can only be regarded for guidance.

The calculation is carried out by using the fuel tank sender and the total mileage completed since last reset...so if you are on a side slope (even a slight one) the fuel gauge sender gives incorrect information for that part of the journey, or if there are long up/down hill sections, again the information used would be incorrect....I estimate the error could be around the 10-15% or even up to the 20% mark in some cases.

Best to use the Brim to Brim method by filling up, do some miles, then fill up again and note the fuel quantity used.

My Previous V8 P38's were doing 14-16 around town and I managed to get 22 on a run once...but so very rare....

I thought the trip computer worked out the mpg from the pulses recorded by the fuel injectors. I know mine is fairly accurate because at the moment its showing 13.7

and having covered 215 miles since the last fill know it wants some more very soon

Although the brim it and mileage test will always be the most accurate recording.

But 14.2 on a run means your trip comp is way out or your RR is not very well!! How long into the 300 miles did you have to refill, if you didn't I would say your trip comp is knackered.

As a rule I get between 13 and 15 in Outer London traffic, but did manage a tad over 22mpg on a 3,000 mile round trip to Southern Spain (4 on board and fully loaded)

Saint.V8 · Nov 4, 2011

Fortgrange....

Extract from the manual about how the MPG is calculated....

I read it as measured fuel used from tank sender...but could be from injector pulses, as they are supposedly metered 'squirts'....

Anyone have a definitive answer [ with proof...!!!

]

Nickffc · Nov 4, 2011

103 mile run from home in Norfolk....mainly A roads..60mph most of the time...A1(M) from Peterborough to London 60-80mph and giving it the bean now and then £32.....@69p a liter....!!!
........oh yeah...LPG....!...

Nickffc · Nov 4, 2011

works out at 10.1mpg....don't sound that good...but works out at just over 31p a mile
if that was petrol that wold be around 64p a mile.....!

stevebrookman · Nov 5, 2011

Morning all,

According to the trip computer 15.1mpg since I reset it last time around three years ago. Have got 21mpg on a long motorway run and around 17mpg towing before I last reset it. Could be a few mpg less but still much more fun than the wifes Fiesta.

Steve

StuckAgainSteve · Nov 5, 2011

Over the last 5,000 miles I've averaged 20.4mpg (1999 Thor/Bosch) mainly motorway driving, trip computer claims a respectably accurate 20.6.

Noahsark123 · Aug 24, 2020

sarap38 said:
hi can sum 1 plz advise me on roughly what mileage u can acheive on the 4.6 to the gallon as i dont think mines right thanks

RangeRoller dt · Aug 24, 2020

Noahsark123 said:
hi can someone help

What you getting?

I’ve seen 2.?mpg (@Henry_b ).

Bloomin thirsty that boy

Most run on lpg as the 100L tank don’t last long. Unless you tow a bowser with you.

Henry_b · Aug 24, 2020

You should get around 18-25mpg out of a V8 depending on how healthy it is the former being town the latter motorway

Contrary to popular belief if it is doing less than 16 it has an issue..

Unless you're driving like a right bell end.

Mine averages this..

In a mixture of town and A road driving, I reset it every fill up..

Turns out my trip is rather accurate the best i've got is 26 which ain't bad for a pushrod V8

marjon · Aug 24, 2020

Ah

J

RangeRoller dt · Aug 24, 2020

go on J...

marjon · Aug 24, 2020

Henry_b said:
Unless you're driving like a right bell end

RangeRoller dt said:
go on J...

No I would like to not say anything else Incase I end up falling into Henry’s description.

It’s not that bad really and I haven’t really checked cos I don’t care, when she wants to stretch her legs then so be it

J

Henry_b · Aug 24, 2020

marjon said:
No I would like to not say anything else Incase I end up falling into Henry’s description.

It’s not that bad really and I haven’t really checked cos I don’t care, when she wants to stretch her legs then so be it

J

I drive like a bellend occasionally.

Grrrrrr · Aug 25, 2020

RangeRoller dt said:
What you getting?

I’ve seen 2.?mpg (@Henry_b ).
Bloomin thirsty that boy

Most run on lpg as the 100L tank don’t last long. Unless you tow a bowser with you.

Have you seen how old this thread is? I think someone was going for the resurrection record.

RangeRoller dt · Aug 25, 2020

Resurrector Not a new member

New to RR maybe?
If you are worrying about MPG 4.6RV8 is not a wise choice

LR-hobbs · Apr 27, 2025

SAN XL said:
Around town I'm getting 11.2 mpg
however on the motorway on a steady 60-65mph I can get up to 19-20mpg -woo hoo

however that is with 295/30/22 tyres, only slightly (ever so) better when I revert back to my original 18" alloys

I still love it !!

I feel privileged, in my P38 4.0 I'm averaging 18 around town and 24 mpg on a run.

biketeacherdave · Apr 27, 2025

5 years since the last post wow don't expect many replies :vb-groan2:

LR-hobbs · Apr 27, 2025

biketeacherdave said:
5 years since the last post wow don't expect many replies

Il try my luck

Datatek · Apr 28, 2025

LR-hobbs said:
I feel privileged, in my P38 4.0 I'm averaging 18 around town and 24 mpg on a run.

Brim to brim or from the dash read out? If the latter, enjoy your dream.

fuel consumption p38 4.6

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