1.8GL fuel economy issues

[ichbintk]

With my '96 mk3 gl ( 1.8 ) i can only seem to get 30mpg tops. I dont thrash it, although a lot of my driving is around town etc. Could anyone tell me what the usual mpg for this model is? Cheers, Tom

[boneybradley]

Ahhhh mpg issue's

My 2.0 8v show's 25mpg as average but 35-38 on a run.... how have you got your figure's??? are they shown on mfa???

[ichbintk]

I worked it out by putting £5 worth of petrol in and seeing how far I got before the needle got to its previous position. However, this may not be too accurate as the fuel gauge sometimes drops by a gallon or so then gradually rises over the next couple of hours worth of driving. Is this a problem? If so, how expensive is it likely to be?
Cheers - Tom
P.S. Whats MFA?

[EvilScotsman]

The MFA is the multi function komputer (lol) that tells you mpg, oil temp, time and distance etc. Its a button on the end of the wiper stalk and a switch on the front of it. If you dont have this you dont have the MFA.

My 2.0 8v is the same as boneys as per mileage but when its cold in the morning it starts at 4.1 mpg going to the paper shop, and 25 by the time i get to work 7 miles away. Journeys of 15 miles or more will see 32.

Could be the lambda sensor causing overfuelling by reading weak. Take out the plugs and see if they are sooty. I have the same weird fuel gauge behaviour lately too - odd!

[rubjonny]

if you think you're burning too much fuel, 1st thing to do is replace the ECU temp sender with a new one from VW (blue 2 pin jobber on a 1.8 GL I think, your dealer will confirm)
Next is the lambda probe, don't bother with cheap no-name ones tho I fitted one and it lasted a couple of weeks!
Get a bosch universal one off ebay

[percymon]

your £5 of fuel is a very inaccurate measure, as you're only buying just over a gallon of fuel for that nowadays 

Suggest you fill the tank and run it to a quarter, or if it has a low fuel light until that comes on and then refill and work it out from the refill number of litres and the trip mileage.

You will also get more mpg using shell superunleaded - its 6% more expensive than std Shell, but i've always achieved 8-10% more mpg in any car i've used it in, based on mostly commuting type trips.

As an aside - i worked it out for my TDi at the weekend, again short commutes, trips to shops and the odd , but enthusiastic    A road jaunt - 49mpg - well chuffed 

[ichbintk]

Is this lambda sensor easy to get to? This is my first car and I dont have a garage to work in. Also, what is the rough cost of a new one? Also, is the ECU temp sender expensive/hard to get at?
Cheers, Tom

[adyh]

Seriously , don't do anything until you have filled a full tank of fuel up and done some mileage .

[rubjonny]

the lambda is in the exhaust in front of the cat normally, you should be able to get it out by jacking up the car a little & supporting it, or just drive it up some ramps.  Saying that my gfs MK3 polo was so high I didnt even have to do that!

The ECU temp sender will cost about £13 if its the 2pin blue type, and maybe up to £30 if its the 4 pin type.  Dead easy to fit though, make sure the engine is stone cold, pop out the retaining clip, swap the rubber seal to the new one and refit.  Its located in the coolant flange on the front of the head

[ichbintk]

Alright thanks, i'll try the full tank solution first and then will try the other options. Are the other two solutions in the heynes manual?
Cheers, Tom