Poor fuel economy on my 2002 TD5 Auto Discovery

[CJ1]

Hi,

I have a late 2002 Land Rover Discovery TD5 Auto. And a previously had an early 2002 TD5 Auto Discovery.

My early 2002 Disco was achieving between 32 and 38 mpg on average.

But my current Disco is only getting between 24 and 27 mpg on average.

The only major difference I know of is my first one had air suspension and my current one has been converted to springs on the rear.

Other then that they are both the same spec even the same colour.

I have even gone as far as putting the same psi as always do in my 4x4's all round and the engine seems fine. I have already covered over 600 miles in it.

Any ideas as to why such a difference in the fuel economy?

Cheers.

[Rangy35]

Are they performing the same, more or less or is the new vehicle better or worse than the previous. There could be a few things to check, air filter, tyre and rim size, service history or more the repair history, t/box ratio, egr valve, for starters.

Well these are the things I would check.

[Anderzander]

38 mpg seems phenomenal !

I've gone the other way - from a Td5 90 doing 28mpg to another one doing 31mpg.

Whilst it is affected by tyres, running gear condition, and servicing - you do also seem to get engines that just perform better than others.

Here are Parkers figures : http://www.parkers.co.uk/cars/reviews/facts-and-figures/land-rover/discovery/station-wagon-1998/running-costs/

[CJ1]

Gear change is better, it seems a little quicker, tyres and wheels are the same size, the engine runs a lot better although I am sure it makes a much louder woosh sound more of the time like the viscous fan is spinning fast all the time where as my last td5 seemed quieter. Could just be me over thinking it though. But at the same time this engine isn't adjusting the rear suspension as and when the other did as it is a coil conversion and so far I have had a lot less stuff in this one including not lugging my tools around. It was last serviced end of 2013 less than a couple of hundred miles done between the service and when I bought it. And I live on cruise control where I can to also save fuel. I know the Disco had a shock when I picked it up, it went from doing virtually nothing for 8 months to a massive 70 mph motorway journey in 1 day. I guess it is a case of service time again.

[RedLineMike]

38mpg out a td5 auto seems like a huge ask,

Cruise control on a td5 auto also hammers the fuel economy

[Shackleton]

I put €50 (33.78 litres/7.5gal @ €1.48 p/l) in mine on Monday 15th Sept. I'm in imminent danger of being left on the side of the road trying to squeeze every last mile out of it. It's done 210.1 miles as of this morning. I'll be lucky to get the 6 miles to the nearest service station. So that's a little over the parkers figures at 27.98mpg. Over half that distance is tipping around the local villages and the 12 mile round trip to the nearest town. I do 53mph max urban, 65-70 on motorways. 80mph if in a rush and overtaking. I did 85mph for about 10 seconds during that 210.1 while testing my waste gate. I think it might make 30mpg if it was predominantly motorway.

It's a D2 Td5 Auto 5 seat with dual long range (steel) tanks, and some debatably relevant stuff like full length roof bars with cross bars and HD suspension. Just done head gasket, injector seals, new FPR & filter, new fuel filter, air filter, fresh oil, EGR blanked, brakes fully serviced all round. The auto box has seen better days but doesn't seem detrimental to progress, the rest of the drive train is 100%. Also I use cruise everywhere possible.

Anderzander's being polite, if you were getting 32-38mpg from your first D2 auto I hope you got paid for it because it was a special car! My RRC with a Td5 (manual) in it, is comparable in weight to a D90 Td5 and is on tall tyres. I don't do more than 65mph in that either and the best it's ever done - on a 500 mile predominantly motorway run between Biarritz and Cherbourg - was about 33mpg. That was with two surfboards on the roof and a boot full of associated gear.

I know from my own wishful thinking that it's easy to over estimate mpg, but I think the reality of the Td5, during average use in a standard LR, is 28mpg low end and best case scenario; 32mpg. I've been considering an overdrive for my RRC now for a while and I think I could squeeze 35mpg with that.

You're viscous unit might be seized if it seems to be spinning earlier, and if the car feels faster then maybe you're using more fuel because you're enjoying yourself

[CwazyWabbit]

Not sure if it's been mentioned but perhaps one of the D2's had some ECU work done?

[CJ1]

I always check mileage and how much to fill to the brim and get it calculated on line. And not sure if last one was tuned or not.

[duncmc]

The 2002 spec Disco TD5 auto that I had from new only every did 27mpg at the very very best. And average mpg was 24.5 over the 63000 miles that we had it for.

So what you are currently getting sounds spot on, compared to ours.

[IanS]

Over the 40,000 miles I've had mine it's done a cumulative 22 mpg. It's generally either around town, on the motorway at 70 mph or towing a 1400 Kg caravan (for perhaps 20% of the time). I've never approached the high figures some people achieve.

[Anderzander]

Anderzander's being polite,

You're right

[Scotts90]

My 51 and 03 td5 D2s both did about 20 around town, average was 23-25 and maybe just scraped 30 on a long run. Both 7 seaters/rear air and manual.

[Shackleton]

Never heard so many low figures. Be interested to know if the above were manual or auto - duncmc, IanS, Scotts90?

There's been a marked difference in my auto since I serviced the whole fuelling system, my fuel needle is much much slower to drop these days.

( Anderzander )

[RedLineMike]

my d2 is a manual with an agressive map, exhaust, intercooler etc, when towing it is about 19/20mpg but then it doesnt hang about with 2600kg on the back,

on a run to scotland last year empty as such with kumho Mts it made 28mpg & on the same run with road tyres turned 30mpg,

[Tanuki]

First thing I'd do is give it an "Italian Tune-up" - otherwise known as 50 miles of "drive it like you stole it" - holding it in intermediate gears for some blasts of full-throttle acceleration until you feel the rev-limiter cutting in. This can shift accumulated soot in the exhaust-system and generally blow out the cobwebs. Remember, you can't over-rev a modern Diesel!

Then- check your driving style: cruise-control can make life easy on the driver but hard on the car - it can't see in advance an approaching hill or set of twisty-bits and do the necessary downward gearchanges to keep the engine spinning freely - it can only wind on more and more fuel in a desperate attempt to maintain forward speed, to the point where the engine's running below the torque-peak with spectacular loss of efficiency.

Also - check for binding brakes: a 'tight' caliper that's not letting the pads move back freely can easily lose you 1-2MPG. And finally check the engine temperature: tired thermostats that open too soon will rob you of both MPG and engine-life.

[Fuel-consumption reference-point: I get about 24-25MPG out of a manual 2001 90TD5 - if I take it carefully. When enjoying myself on the motorways, under-20MPG is more like it - but a Defender's not got 80MPH-plus-friendly aerodynamics]

[Wingnut]

Check your Mass Air Flow meter, mine went down to 19 mpg on a recent trip to Scotland with the caravan behind, quite a bit of off road driving and a little touring around.

When we got home I checked the MAF and sure enough it was no longer giving any info to the ecu. Changed it for a genuine parts unit and on the next fuel check the consumption had dropped to 17 mpg !

I've changed the engine wiring harness (a horrible job on a Discovery) and I seem to be back up to around 23 mpg. If you have any evidence of oil contamination in the red plug at the ECU then I would suggest you change the engine wiring harness as the presence of oil can impede the passing of correct information from the engine to the ecu and vice versa. (I am taking it for granted that if there is oil at the red ecu plug you will change the injector harness)

All the above is on a 1999 MY Discovery, chipped, larger intercooler fitted, de-egr'ed and milage corrected for larger mud terrain tyres.

Peter.

[IanS]

Never heard so many low figures. Be interested to know if the above were manual or auto - duncmc, IanS, Scotts90?

Mine's an auto and I do use cruise control all the time on motorway / dual carriageway. Set at an indicated 73 mph (63 when towing).

[CJ1]

WOW, that was all a very interesting read. After I have done the London to Brighton run on the 5th, I will change the fuel filter and stick some diesel fuel system cleaner through the system and see what difference that makes. I don't tend to do a great deal of short journeys. The average trip out is normally a minimum of 35 miles round trip as I don't shop in my local town as everything is tourist prices all year round. So usually about half an hour to the nearest town. And I normally go the most level and steady route and do a lot of driving at around 60mph so get to use cruise a lot. As for the comment about cruise control making cars drink fuel. Will I have to say that is a load of old bol**x. Every car I have had with cruise and that is more than I can remember have always been better on fuel as the car is made to do a steady speed and the cruise control is designed for a car to remain at 1 speed without too much pressure on the accelerator meaning that less fuel is forced through and mostly only the right amount is pushed through.

I will have to also give my car a service too and see what that does to fuel economy. My temperature gauge sits about 1mm higher than the half way mark where as my last Disco only sat on the half way mark.

Thank you for all your comments. They have all helped me in one way or another.

[dave88sw]

You said earlier on in the replies that it makes a whoosh sound like the viscous fan is being used more. Is it in fact seized? This will make a marked difference to fuel economy.

[RedLineMike]

With the cruise control activated the road speed stays constant, but the engine load varies thus why it will use more fuel on the cruise control on a td5 auto

[CJ1]

You said earlier on in the replies that it makes a whoosh sound like the viscous fan is being used more. Is it in fact seized? This will make a marked difference to fuel economy.

I didn't even consider that. Cheers. I will have a look on Saturday evening when I am on my way up to London. I will check before I leave and at the services on the way up and see. Or is there an easier way to test it? Cheers

[Shackleton]

Just above the centre line, or more accurately just above the top line of the water level symbol on the temp gauge is normal, that's if mine's anything to go by. That's where it's always sat, both before and after a replaced head gasket.

About the cruise control. I could understand someone being disillusioned with it, or having experienced diminished fuel economy if they were using it on a manual car. But cruise on an automatic is definitely fuel saving over a distance, Land Rover or not. Yes if you're on a road with recurring steep inclines then it might not be prudent to use CC. But on your average motorway I've found it'll give me at least 2mpg over using my (very reserved) right foot. That's experience collected from 1000's of miles passed in Mercedes, Saabs, BMW's and LR's.

To make the most of it though you have to drive the CC. As in anticipate well so you don't have to kick out of it... consistency definitely brings economy.

EDIT: If you pop the bonnet, with the engine cold you should be able to easily turn the fan by hand. If it offers resistance then it's not in great nick. If it just won't move without turning the pulley it's on, it's seized.

[AMB]

I find 32-38mpg out of a Td5 Auto incredible and would suspect the odometer gearing on your first Disco. Manufacturers figures are notoriously optimistic and they claim 27 for the auto and 30 for the manual.

My experience on other cars would suggest that cruise control is slightly less efficient than a light right foot plus anticipation. However, that experience also highlighted vast differences in the capability of the cruise control. I agree that pairing it with a good auto box is likely to have less effect on mpg than lazy use with a manual.

[CJ1]

The Viscous fan isn't seized. I have put Wynns fuel system treatment in and the fuel economy has improved slightly. On the London to Brighton run I filled it to the brim to the 2nd click not the first. I did a total of 272 miles and I filled it up again on the way home. 272 miles was the reading after I reset the trip meter on the 1st refill. I filled it to the brim again and I got 272 miles out of £42 of diesel at 128.9p a litre.

I haven't worked the MPG out yet on those figures.

The 272 miles consisted of Motorway driving and town driving where on quite a few occasions where I got stuck on red lights I had to floor it to catch up with the convoy in small stages, but mostly steady driving.

I haven't changed the fuel filter yet or checked the Air flow meter either.

[Shackleton]

Well after more tests with mine I've found that just tipping around the village kills my mpg significantly. I only got about 22mpg. All short spins, never locking the TC.

Sounds like you need to do some servicing/investigating though. The fuel filter can make a difference. Did you say your fuel pump is loud? Listen to it for pitch and sound volume before you change the filter. There can be a big drop in the noise of the pump if the filter was stuffed.

btw how many litres is a standard Disco tank?