Gazellio wrote:

I have noticed that on my 3.0 V6 CRD 300c the fuel consumption figures are much better when travelling quite fast and 75-80mph seems about the best!

On a trip I get 35 mph+ and about 28 mpg urban mix....

Not sure if the same is the case with the TDV8.

Having read this post i am interested in the mpg figures quoted for the TDV8 as i bought a 56 plate a week ago with 52k miles and in fine condition. After 1 week of mixed motorway, country lane and a bit of town my mpg on the screen says 20.9 despite resetting.

I am surprised and a little dissapointed by this figure having paid a fair bit more for the TDV8 over the same year S/C for what id hoped was 25 mpg or better.

Im not driving flat out or anything like that and in my RRS S/C i would see around 15.9 for the same journey

Update: I took the motorway to work this morning to see how the mpg would work out, its a 20 mile trip with about 17 miles being motorway. I reset as i hit the motorway and through the 50 mph area the mpg went to 28 mpg max then decreased to 25.5 mpg for the 70 mph area. It seemed to settle at 25 ish for the duration.

I am sure this is low based on the figures in the sales literature for the TDV8, what are others getting on this sort of run?.

The RR runs well and doesn't feel like it needs service work since it was serviced in Feb 11, would using the incorrect / poor quality oil have an impact on the mpg?.

I have 22" wheels fitted with brand new tyres but i cant believe that would be the cause

from reading previous posts relating to mpg figures ,these are on the low side ...at a constant 50 mph you should be getting at least low 30's...the wheel size doesn't make any significant difference..

That's what i thought, what could be causing the low mpg?

not sure , but i would check the air filter and even consider a remap ..

Right. Steady 55mph and force it into 6th with the command shift. Mine does 36mpg like this. Another thing to check is a brim to brim fill up calculation. The thing on the dash is not always accurate.

If you can't get over 30 doing the above then get it checked over at the dealer 'cos something's wrong.

Cheers gents, i will do the above and check again.

Does using supermarket diesel as opposed to branded such as Shell, BP etc have any influence on this?.

I have been driving steady this past week or so and don't get anything like 36 mpg on a run at 55 mpg, im getting 32 at best, being very gentle with her and around 25 on a combined cycle but this needs to include more motorway driving at a steady 70 mph than my usual country lane / town driving.

I still think its low.

One thing i keep doing (75% of the time) by mistake is firing her up without waiting for the glow plug light to go out, will this affect how the engine performs?.

Interesting stuff this.

I'm not particularly attentive to fuel consumption and I don't like limiting my driving experience by say, driving at 50mph for long distances, just to improve the mpg. I find its always better than 25mpg on my commute to work (less than 20 miles half of which is on a busy motorway and just over 30mph on a long run at down the motorway at between 60-80mph.

I have to say I am however paranoid about getting the money off promo's at supermarket, particulary as Tesco now allow up to three vouchers to be used in one go (15p/litre off).

I do still wonder if the TD6 I didn't buy at half the price, twice the mileage and probably better looked after would have been a better buy and it was only a year older, particularly as I drive like an old wuss.  Geoff

I get better than those figures with a TD6 so maybe its due a good service and possibly ECU reset/update??

I'm driving like this to carry out the comparison, its not the be all end all for me but i am keen to know that its doing what it should especially since i am a petrol head historically and didn't buy a S/C for mpg reasons only.

Next step is to check the air filter / oil etc but how would i reset the ECU, is it dealer stuff or can i do it?.

IIRC from posts on here disconnecting the battery for a few hours can do this but don't quote me on it...

There's an interesting question here, anyone got an opinion .

Which is the most economical:
a.Cruising the motorways at the max torque point , just over 2000rpm (about 70mph) or
b.Manually changing into 6th as early as possibe? Geoff

Early as possible as max torque is under full throttle, not low throttle.

Idealy you'd need it on a rolling road to see where the most consistant low torque off boost threshold is.

Id change up as soon as possible as diesels are most economical at very low revs with hardly any throttle opening.