Any input please ? A bit of a long thread I'm afraid....

I've got an early 3.6 TDv8 that I've now had for 6 years. It's a Nov 2006 car with approx 140,000 miles.
I never expected much for fuel economy - it's a nearly 3 ton tank with poor aerodynamics & we use it mainly locally
However, on long journeys it doesn't improve that much and seems to be a lot lower than some of the reported mpg figures on here & elsewhere.

At best I see 25 mpg average on 50 mile plus motorway journey's - via the mpg display & after re-setting at the start of the journey. I have seen values above 30 mpg - but they've only been for seconds after re-setting the mpg display & while almost not using the throttle. Likewise, the average has crept upto nearly 27 mpg a few times for minutes if locked in traffic doing a constant 60 mph.
Quite often though it doesn't get above 22 mpg average on these journeys.

I use the cruise control a lot when on motorway journeys & I'm not a heavy throttle user (I've got another car for fun ). The car gets regular servicing, tyre pressures are checked regularly & there are no faults or updates identified via my GAP IID tool.
I changed from Pirelli Scorpion Verde to General Grabber AT tyres 18 months ago, but there was almost no impact on mpg.

As the car is amongst the earliest 3.6s, I was starting to wonder if the much higher mpg values reported are later cars & whether Land Rover might have improved the engine control / fuel system control software on later cars ?

Apart from getting a software remap to add performance / economy, has anyone had the engine ECU / Control Module software updated on an earlier car ?

Generally, I operate on a "Don't mess with it if it works" strategy with software. But I'm no longer sure if it works as well as it might be able to.

The GAP tool doesn't identify any ECU / ECM updates available - but I'm unclear whether it should or not.

Any thoughts ?



If it helps anyone, The GAP IID identifies the following Engine ECU info

PCM-Engine TDV8 (No update found)
Assembly (F113) : NNW506880
Calibration (F124) : NNS505000 - 4248
Hardware (F191) : NNN500970 = Up-to-date
Serial : 867038252
Strategy (F188) : NNV504560 = Up-to-date Paul,
2001 Discovery 2 TD5, 211,000 miles & climbing
2006 FFRR TDV8 Vogue 145,000 miles & climbing
Member of Midland (Land) Rover Owners Club, www.mroc.co.uk

Never heard of any major economy gains getting it updated. What's your actual mpg as measured by miles vs a tank filled to the brim? Are you running standard size tyres? The only mod worth doing is getting the EGR software delete from BAS (+ blanking plates from ebay) which may help esp is the valves are not operating properly. 2012 TDV8 Vogue (L322)

JayGee,
thanks for the response.

I haven't tried measuring tank to tank. Unfortunately the car has a faulty fuel tank sender at the moment, so very difficult to judge how much is in there
Is the mpg display known to be inaccurate ?
I know it's effected by tyre size, but I assumed that it uses a fairly accurate knowledge of fuel use via the fuel injection parameters.

Tyres are slightly oversize "standard" L405 255/60 x 20s - but should only cause the display to under-read by 3% on mpg vs the "original" 255/55 x 20s.

However, your question made me challenge what was sold with the car & I've discovered it was 255/55 x 19 ! so my under read error may be 6% - which is significantly more & might mean my mpg figures are closer to other reported values than I thought . Displayed 27 mpg = actual 28.6 mpg.

Ref EGRs : They've been blanked off for a few years now. No obvious effect on mpg after blanking off & inspection of the valve head operation showed no obvious problem or sticking.
As you suggest, a BAS re-map with EGR electronic delete is a next step (I've been putting it off for no good reason other than laziness - lol)

I think your "prod" ref tyres might be the key point.
When I have the fuel sender fixed, "full tank to full tank" calculation may well show I haven't got a problem

Paul Paul,
2001 Discovery 2 TD5, 211,000 miles & climbing
2006 FFRR TDV8 Vogue 145,000 miles & climbing
Member of Midland (Land) Rover Owners Club, www.mroc.co.uk

A 60 profile is nearly 7% bigger than stock so your mpg calculation will be well down and also your speedo will be under reading significantly. The difference between driving at 65 and 75 will have a significant improvement in mpg due to the wind resistance changing exponentially with speed. No need to have a working fuel gauge as you just fill till the autostop on the pump and reset the trip then refilll to the same and record the trip mileage and do the maths. 2012 TDV8 Vogue (L322)

Personal opinion but I rarely use cruise control. I find it a pain as in traffic you are consantly checking speed because the speed of person in front of you is rarely constant ( adaptive cruise control might overcome that). I also don’t find it to be an economical mode. Better throtle control without it.

As I said, my personal opinion.🙂 John
2008 Stornoway Grey 3.6 Tdv8 Vogue
2005 TD6 Java Black Vogue - Written off!!
GAP iiD BT
2003 Discovery TD5 Auto, Nanocom Evolution - gone to a new home!
MasseyFerguson 152 - No electronics!! - Sold

Cruise control is not meant to be used 'in traffic' for safety above all else hence why adaptive systems are now the norm which can adjust the speed and automatically brake. 2012 TDV8 Vogue (L322)

I understand that. I am talking about motorway use. John
2008 Stornoway Grey 3.6 Tdv8 Vogue
2005 TD6 Java Black Vogue - Written off!!
GAP iiD BT
2003 Discovery TD5 Auto, Nanocom Evolution - gone to a new home!
MasseyFerguson 152 - No electronics!! - Sold

So am I and I only use cruise when it's very quiet. 2012 TDV8 Vogue (L322)

Hello Paul.

As you know, I had a 3.6 TDV8.

I did a 3,000 mile round trip (4 days actual driving) in the winter, all good French and Spanish quiet roads once out of England. 3 passengers plus me, 4 small suitcases. Kept mainly to speed limits or below (was foggy at times!) and averaged...... 23mpg. Was hoping for 30+

I also used to commute into the city centre (Birmingham) and got 20-22mpg. __
2018 L405 3.0 TDV6 Vogue SE Fuji White
2000 4.6 V8 HSE Oxford Blue
1994 3.9 V8 Vogue Ardennes Green - resto project

Land Rover History:
2010 3.6 TDV8 Autobiography Stornoway Grey
2001 Discovery 2 TD5 GS
1999 Discovery 2 V8i XS
1994 Discovery 300Tdi
1993 Discovery 200Tdi
1989 Range Rover Vogue SE 3.5EFi
1976 Series 3 2.25
1977 Range Rover 2 door 3.5 Carb

I have owned my FF over three years now and using it daily around town it averages 22/23 mpg and on a long motorway run she will hit up to 32mpg. I blanked the EGR's off about a year after I bought it but didn't notice any difference to the fuel economy at all. It's a heavy vehicle with the aerodynamics of a concrete block so I never expected it to be economical, just the most comfortable vehicle I've ever owned. My advice is to look after and enjoy what you have! Current collection :

2007 Vogue TDV8 Stornoway grey, black on black
1982 JCB Sitemaster (resto)
1970 MGB
BMW R1200GS

JayGee wrote:

So am I and I only use cruise when it's very quiet.

Mine is a 07 tdv8,140k old. Averages 24+ all local short journeys unless trip computer is wrong. Stock car, no egr blanking/mapping etc.
If you are getting 22-23 mpg on long journeys, then its a bit low tbh

Average mpg is also very much down to how it's driven. Always accelerating 'briskly' and cruising above 70mph on the m-way will hit mpg hard. 2012 TDV8 Vogue (L322)

Pawl wrote:

Tyres are slightly oversize "standard" L405 255/60 x 20s - but should only cause the display to under-read by 3% on mpg vs the "original" 255/55 x 20s.

However, your question made me challenge what was sold with the car & I've discovered it was 255/55 x 19

Another user here of adaptive cruise control all the time. Takes the effort out of long distance motorway journeys especially when heavy traffic.