MPG

[Dadad]

I'm new to BX ownership, having just bought a 1990 8v GTi. The tank holds 66 litres, about 14.5 gallons, and has just emptied itself after 250 miles, which means it's doing about 17 mpg. The brakes are not binding, so can anybody offer me some advice as to how to improve the mpg. Thanks.

[Tinkley]

The 'Official' mixed running figure is 34 mpg for that car, if a pre cat one. You should be able to get close, unless a) short trips, b) heavy right foot, c) something wrong in the system. Assuming the latter, just go through the usual suspects, plugs, leads, air filter, timing - maybe even cam timing. Make sure any sensors feeding the ECU are good and that any over fuelling is actually going back to the tank. Also check the steel fuel pipes (under o/s sill) are not corroded and leaking a common thing on the cars this age, whether petrol or diesel.
Not sure how to test the ECU but expect someone on here may be able to help you on that score.

At this time of year I think you should get around 30-32mpg with a better figure in the warm summer weather, but I get better than the average claimed on my 1.6 petrol (carb) but with a fairly gentle right foot - well most of the time....
Tyres ie make, may also make a 1-2mpg difference but they won't halve the consumption.

[Philip Chidlow]

20-23 around town on short trips and max of 34mpg on mine (mind you it was an auto).

[rutter123]

I get around 26/28mpg urban and up to 32/34mpg (jetronic system) motorway at steady 65mph, heavy right foot low 20's ish i would guess.
17mpg does seem quite low but acheivable if you are whipping its arse hard enough. Out of interest which ignition system jetronic or motronic? Regular or super unleaded? Have you checked your ignition timing/compression etc?
Try driving it by keeping the rpm's under 3k's and see what you get then.

[Kitch]

16v manages 25mpg with ease around town, so something's not right! Mind you that's Motronic, which is a lot more advanced than Jetronic.

[Tim Leech]

Did you brim it and run it until it stopped? The bigger tanks have a reserve tank which holds quite a bit.

Has the car been recently serviced? Also I would put it on a gas tester.

[rutter123]

In the mid 90's my then wife and i both had Vauxhall Cavalier MK2's with the 1.8i engine both pretty much identical cars, both manual with less than a year between them, both similar mileage 70k and doing similar journeys, yet one would average 30/32 mpg and the other only 24/25 even after swapping over cars for a month the results were the same, both blew roughly the same on the gas test and no mechanical faults, i tend to ignore factory figures, you get wot u get.

[Dadad]

Thanks very much for all these helpful suggestions. I haven't been driving like a boy racer, so I'll check out all the points you've made. Incidentally, the engine is the same as that in my Peugeot 205 GTi and that gives me just over 30mpg, even driven hard.

[MULLEY]

Faulty injectors?

[kiwi]

To acurately measure fuel consumption you need to base it on at least 3 fills driven about 200 miles apart! A fill being to the brim and mileage and litres recorded. Most miscalculations then occur converting from litres to gallons! After all these years I am still surprised that miles of km per litre is not used asa 3rd alternative of measure.

[MULLEY]

I'm assuming its a manual rather than an auto?

[MULLEY]

My 16v i managed to get almost 42mpg out of it doing 4 2hr runs doing about 50-60mph, otherwise i think it was still doing just over 30mpg when i was caning it, so you've deffo got a problem with that amount of fuel economy

[Dadad]

Took it to my local Peugeot specialist who recognised the engine and attached it to his MoT exhaust gas analyser equipment. He said the readings were 'off the scale'

The CO max limit is 3.5% for this engine and after his adjustment it now reads 0.76%. Similarly, the HC max limit is 1200 ppm and now reads 161 after adjustment.

Running a full fuel tank, I've got to 165 miles and the fuel guage is not even down to the 3/4 mark yet, so I guess it's problem solved, although there may be some performance sacrifice to get these figures; time will tell.

Thanks for all your help.

[Way2go]

The CO max limit is 3.5% for this engine and after his adjustment it now reads 0.76%. Similarly, the HC max limit is 1200 ppm and now reads 161 after adjustment.

Curious... Had the "Tamperproof Screws" been tampered with previously? Also was it just an adjustment of the screws or did they perform a remap of the ECU too?

Also strange that he has set CO to 0.76% when the BX spec for the Motronic 3.1 is 1 to 2%. For the earlier Jetronic it is 2%. This could have adverse implications for engine wear.

[rutter123]

Did you ever check the condition of the spark plugs? This is usually a good indication of wots goin on inside,