Drastic mpg

Ok, I admit I need help now, done the old fill to the brim and run it almost dry over a period of months now and every time come back at 350-360 miles to a tank that works out at 17.5 mpg. She has had full service, K & N filter, Electric fan, fuel additive regularly, egr blanked and de cat and just dont know what to do now. Its an auto but Im not towing nor thrashing it so assuming its a fuel problem, Its not smoking on hills or start up so nothing to do with mix as far as I am aware......Please please please if anyone can point me in the right direction as Mr Browns tax on fuel is crippling me lol. Oh and Cruise control has packed in also for no good reason

Hi there, I had a '98 TDi 300 auto with the same mods as you and I got 550mls on a tank and over the 16,000mls I had her, she averaged 33mpg !!


To be honest I'm a bit stunned, driving style can make a big difference but this is huge. What types of usage do you have - is it all town driving or a mix?

Have you changed the tyres for a non std size? Have you changed the cambelt recently?

The word Auto is the problem. Mine does about 21-22 around town and 24-25 on a long trip. But my 200 manual will do more like 25-28 around town
My criuse control don't work as well but I don't care

666 george said:

The word Auto is the problem. Mine does about 21-22 around town and 24-25 on a long trip. But my 200 manual will do more like 25-28 around town
My criuse control don't work as well but I don't care

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Hi George, mine was an auto and I didn't find that a problem, as you can see in my post above.

i also have a Jap import 300Tdi auto and over the last 5 years it has averaged 23/25mpg with mainly local short run mileage.Can get 28mpg on long run if kept below 70. Check the vacuum pipes for the cruise control as the sometimes perish.If split at ends can be shortened but if not replace with reinforced fuel pipe, much stronger. Good luck on your milage

Must be something wrong with it. My old 94 auto did 23.5 mpg pulling my 1200 kg caravan with four bikes on the roof last summer on the Cornwall run. I think it did 420 miles on a tank full.Have you checked exhaust ?

Thanks for all the ideas, yes Cam belt just changed.....Tyres standard, whats your thoughts? I am mainly using it for work in the city so not ideal but on weekends try to get a nice 60 mile trip out of her, it has to be something as I have heard so many others say about mpg being around 22-25. Whoever can help, please do Ill be in your debt lol!

Matillda 300tdi said:

Thanks for all the ideas, yes Cam belt just changed.....Tyres standard, whats your thoughts? I am mainly using it for work in the city so not ideal but on weekends try to get a nice 60 mile trip out of her, it has to be something as I have heard so many others say about mpg being around 22-25. Whoever can help, please do Ill be in your debt lol!

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It's a process of elimination. Has the fuel consumption always been this bad? I accept that autos round town can be heavy, but diesel engines in this role are usually better than petrol, so on balance you should be getting more than your current figures - assuming they are accurate of course.

I asked about the cambelt as if not properly done can render the engine less efficient. Do you have any means of checking the cam timing?

When you did the service did you clean the sedimenter? (in the rear wheel well and removed via the nut on the top with 11mm spanner).

Also to try and save some £££s put a little veg oil in. I currently run 60/40 diesel/veg mix in the tank. but have ran 50/50 at times (even put a bit of petrol in at one time but thats another story :doh: )

thebiglad said:

It's a process of elimination. Has the fuel consumption always been this bad? I accept that autos round town can be heavy, but diesel engines in this role are usually better than petrol, so on balance you should be getting more than your current figures - assuming they are accurate of course.

I asked about the cambelt as if not properly done can render the engine less efficient. Do you have any means of checking the cam timing?

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I don't mate, I know the bloke who done it had a headache, its a possibility....Yeah its always been heavy since I bought it, just never thought she would drink as much.
No havent done the sedimenter to be honest, its on my list of things to do but shouldnt imagine it would make a huge difference?