Yikes - mpg

Now I get to drive my beasty I've gone through a couple of tanks of fuel and get 15mpg on mostly very short urban runs, and 18mpg on a 60-80 mph m-way cruise ( although I use the word 'cruise' advisedly what with my overdrive not working :) )

Is this to be expected?. Not really fussed - its not like its costing me a fortune in HP repayments, just like to know what similar 760's tend to get lack of economy wise.

Hmmm...... me thinks you've got a problem here x(

Let us Start at the beginning, are you sitting Comfortably?? Gewd!

Once upon a time there was an Estate and a saloon model, the saloon looked Oh so grand, but the Estate always thought it was the saloons big brother,Both by size and capacity.

One day The saloon decided to prove the Estate wrong and challenged the estate to a drinking competition at the local watering hole. The estate agreed.

At the local pub they met and ordered the first round. The challenge started and for a while it was neck and neck, both cars swallowing merrily..then the Estate started to wane and complain of "Bloatedness" The saloon smiled and Drank on. At the end The amount consumed was measured, The Estate had drunk 60litres and felt confident he'd won... Until the saloon Stepped up to the plate AND... A Whopping 80 litres had been consumed with no side effects what so ever!! The Estate rolled away quitely feeling slightly "Deflated" and "let down" That he hadn't won the day :o

Anyway now that we've Established that the saloon hold more fuel than the Estate ( Taken from the owners handbook under "capacities" )


We now need to look at a few things more seriously..

1/ When was the car last serviced - plugs, Dizzy Cap, rotor arm, ALL Filters (oil, fuel, air)? what condition are they in? Sooted up? oily? etc


2/ How does the car run? Sluggish on pickup or crisp and picks away under harsh acceleration? Idle lumpy?

3/Fuel pumps (Yep! There are Two on this car) Working ok, or does the car struggle under load?

4/Has the car been tuned at all? The AFM is adjustable and should be set just below 1% say 0.75% Co.

5/ Now for the fun part.... Remove the AFM on the air intake side and clean with Wynns Carb Cleaner (Or Similar) then leave to one side. Moving further back, remove the ducting up to the Trottle body. Now Spray the throttle body, If necessary remove the throttle, bearing in mind that a new gasket (paper) is needed here. SPRAY BOTH SIDES OF THE BUTTERFLY UNTIL IMMACULATE! When you hold this up to the light there should be a VERY fine line of light around the Disc/ Butterfly and reassemble. Now Remove the PCV valve next to the throttle body (Kind of chrome cylinder shaped object with one black bullet plug on to it) CLEAN WITH CARB CLEANER until immaculate, working the rotary door until clean, then lubricate with a little "3 in 1" oil and reassemble. Don't panic if the idle is high leave it alone for a short while, this is so that the ECU can accept the "New" settings of the PCV. Then Retune.

6/ Look for a product called "ASTA" Fuel Cleaner. It Seriously WORKS. Cleaning out the crud on the fuel lines and "De Glazzing" the injectors as well as cleaning them, it also gives the head a "Seeing" too Decoking the valves a little.

Try all of the above and you should see a positive improvement :D

Mine has just been filled today, a full 60 litres and I checked the mileage just outta curiosity and on town driving alone I obtained.....24mpg which I thought wasn't to bad for a 2.8! My 3.5 BMW in and around town does 18 - 21 on urban cycle so 24 ain't to bad }(


Hope This helps.

Regards
Dave M

Problems , problems.....there are only challenges ;)

1/ Last serviced 10k miles and 2 years ago and laid up a year ago. The oil was like tar, but I've changed the oil filter, oil with 10/40 mineral, and air filter. The old oil was like tar, the air filter was pretty clean. I havent change the fuel filter, plugs etc etc though.

2/ She runs great! She starts on the first twist of the key. I have no complaint about the performance and refinement. I've owned many
types of gas guzzlers, so its not like Im comparing it to a nasty old 4 banger :). After the m-way run the exhaust tail pipe was spotlessly clean. So not running overly rich, or burning oil.

3/ Struggle under load? Well only as far as the OD doesnt work, but shes reved cleanly to 5,500 on the mway (albeit in 2nd gear).

4/ Tuned? I doubt it, just garage servicing upto 140k.

I've only gotten a maximum of 52 litres into my tank. You must reeeeeeaaaaaaallllly wait to fill up - me I get twitchy the moment the light comes on.

When I had a range rover a major cause of excess fuel consumption was the O2 sensors on the cat. These should be replaced at 100k. My beasty is at 150k, so I assume these may also be a culprit.

So really my estate is getting 175 - 210 miles from brimmed tank to red light.

I will look into the TB cleaning later as I have an MOT due in the next week. :(

Cheers for the info - its all appreciated.

I should say that most of the urban runs are very short, some may be upto a couple of miles, but 3 runs a day are as little as just around the next steeet to 1/4 a mile. So shes usually cold. Just in case anyone rips into me (as if eh..) for using a car for such short journeys, 2 of my dogs are old (arthritis/hip dsyplasia etc) and whilst can walk to the park cannot walk back - so there ;)

That said do you still think that 15mpg uban is unreasonable?

I would say once you get that OD working, those figures will go up, as in better... or is that just too duhh!

George

Anglo-Swede resident near Leuven in Belgium

'87 745 GLE Turbo Diesel Intercooler (D24TIC/M46, 200k)
'88 745 Turbo Intercooler (B230FT/M46, 270k)
'88 745 GL (B200E/M47, 200k)
'89 440 GL (B18K, 90k)

[Steve Hogg]

I've only owned my 760 Estate for about 2 months and 2000 miles but my fuel consumption is only slightly better than yours, although it seems to be improving the more I use the car, I suspect it has also had a period of inactivity.

DaveM (kind chap) gave me a 'fix list' similar to yours, which I am working through, I'll post the results on the forum.

Of course if economy is a major issue you don't buy a 760, but once you've driven one economy becomes a secondary issue.

Happy motoring

Steve

Couldn't have put it better myself
cheers Dave

[niloc]

If it makes you feel any better, I get 50-60 miles on £20. But, my right foot is quite heavy!!! :+ (Gotta love the V6 power!!)

Mmmmm, Sounds like Funnnnnn!!!;)

1/ I recommend that you install an engine flush to de "Gunk" the insides of the block.

"Asta" from Ssshh "QVC" works, don't ask, don't go there, as once known then I'd have to kill you ;)

Use Crappie oil and two filters after this, this is because you're going to use the "Crappie" oil as a secondary flush to remove any crap in the sump then drain again. Now fit the second filter and install the Synthetic oil and all will be well.

2/ No comment (Yipppeee!!! :D )

3/ Me suggests that you take the car to a genuine autobox specialist and have the kickdown set up properly as it involves a fair amount of precision, not for the DIY man. This will eliminate the erratic changing of the box. Perhaps a Filter and oil change on this as well?? This costs £94 notes and prolongs the life of the box}( But makes one "L" of a difference to the performance to the car... Been here done this and "WOW" :D


4/ Ulitmately, Engine flush first, then a right good service, Filters, Dizzy Cap, Rotor arm, Plugs and possibly leads. Then set the tappets on the car. Then tuning...and the car won't know what hit it!!!YeeeeHaaah!!! :9


Regarding the OD can I see this relay?? I may have a spare as I've started robbing the breakers of relays n'things that fall in to LARGE Pockets}(

You all do this, before any one has a "pop" at me you're only kidding yourself:7


Regards
Dave M

P.S Keep me posted

Ohhhh! And Remove the cat if it's fitted, only post 1991 have to have a cat, so this can be removed and you're economy will rise.:+

Regards
Dave M