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Disco 1 300TDi Awful MPG


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Hi, I'm after any thoughts on what could be causing bad MPG on my Disco...

Its a 97 300TDi with alomost 200,000 miles on it! It's running 235/85/16 Insa Turbos (so higher rolling radius than standard)

It ran out of Diesel on Saturday and I put £35 in it, since then I put another £20 in and the fuel light came on again this morning on the way to work!?

I'm not sure on how many miles I've actually covered in the last few days, but I'd say it can't be more than 150... £55 of fuel seems a hell of a lot for that many miles!?

So could it be a combination of oversize tyres = more power needed to move them + lots of short journeys (stop start) and the fact it has galactic miles on it, or could something be wrong?

Thanks in advance for any suggestions!

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it does seem to be a lot of fuel for the mileage covered. works out at about 15-20mpg.

as you say, it's more than likely the larger tyres, coupled with the short stop start journeys that is killing your mpg.

when was the fuel filter/sedimenter last cleaned/changed? has it had an oil change recently (last 6k miles)?

if not, then give it a good service, get some injector cleaner and fill the fuel filter with it, then take it for a good run. I always add a bottle of cleaner to the tank as well, and manage about 180-200 miles on £40 diesel (standard size 235/70's - cooper st's, tweaked pump and allisport cooler), which works out at about 28mpg/week communting

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Thats about 19mpg!

Has it suddenly started drinking fuel?

Have you done anything to the engine recently?

Is it smoking black?

Has it got as much power as usual?

Have you got EDC?

Have you blanked of the EGR?

When did you last change the Air filter?

I run 265/70/16 Kuhmo KL71 with big intercooler and increased boost and get 25/28 mpg

Edited by fozsug
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Here goes...

Has it suddenly started drinking fuel? I don't often use it apart from for Pay and Play days and the odd bit of green laning so don't have a comparison really...?

Have you done anything to the engine recently? No mods to the engine - only had it 6 months but as far as I know its 100% standard

Is it smoking black? No smoke at all really

Has it got as much power as usual? It does seem a little under power (I think) but then again my daily car is a 150bhp Leon Cupra TDI - so again can't compare the two

Have you got EDC? No idea what that is!

Have you blanked of the EGR? EGR all there still, but unsure if it works! It's one of the jobs to do at some point

When did you last change the Air filter? Not in the time I've had ot actually - considering the amount of off road driving it's done it may need a change!

Thanks :)

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Also, in response to Fozsug, I haven't changed the oil, but it was quite clean when I got it, so must have been done shortly before then

Again, I've not changed or checked the fuel filter - will have to get one (is sedimenter the same thing?)

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I would, give it a good service, air filter especially as its bound to be full of muck after pay and plays.

Fuel filter is on the bulkhead, when you fit the new one i always fill full of injector cleaner


Sedimenter is on the chassis behind the drvers side rear wheel, it has a plastic drain tap/plug n the bottom to drain it, but its probably seized, so undo the 11mm bolt on the top to split it in half, to clean it out

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A worn lift pump will also give poor MPG. I just had a major fuel starvation issue and in fixing the issue I swapped the lift pump out. I have noticed a marked increase in MPG since I did this and if yours has 200K on it I would maybe look into that.

You can test the lift pump quite easily by just disconnecting the incoming fuel line, hold your finger over the connector on the lift pump and pump the little push handle thingy. If you get a good suction and it doesn't drop off after a couple of seconds then it's probably good. If the suction is weak or it looses suction on its own then it's probably time to replace it.

I also noticed a drop in MPG when I put on a set of AT tyres. Not much, but I can see that a set of muds would hit you harder.

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