97 Golf MK3 has very poor fuel consumption

[beeson]

Hi folks,

I've owned my 97 golf 1.8l for only about 2 months now and I'm getting really bad gas mileage. I average 275 kms per tank...thats only around 20 mpg. So far I've changed the air filter, spark plugs (which looked totally normal before I swapped them, tanish/grey) and I ran injector cleaner in the tank the second last time I filled up. The engine doesn't over heat, and sounds normal. Does anyone have any suggestions before I take it to a mechanic? Thanks in advance.

[BugsyMalone666]

Depends on what sort of driving your doing? Local driving round town (like 2 miles between work and my house) if i do nothing else but that sort of distance with maximums of 5 miles fuel consumption was about 25mpg tops!

when i got my golf several years ago on the first few long runs i did it was averaging 38-42mpg! then i started driving it harder and fuel consumption went down, although when I started seeing my g/f 220 miles away with such long trips i tended to try and economise and saw a maximum of 34mpg!

what i have noticed on the MOT`s is that over the past few years the emissions have gradually been rising very slightly until this year when it was almost a fail!

you say you car doesnt overheat, does it run at about 80-90c? mine was running just off the 5 bars at the bottom on the motorway which means then the engine thinks its still warming up and uses more fuel.

I have since replaced the tthermostat which improved the temperature and also I changed the exhaust oxygen sensor which I havent been able to test on the 220 mile trip yet but local 35 mile runs thrashing it, it still seemed better on fuel although I have yet to take it back to my mechanic/MOT station to test the emissions.

having done a little reading it would appear that as the exhaust sensors age they deteriate causing higher emissions and higher fuel consumption, although what i have read on the internet it reckons they only last about 50k, my golfs on 105k!

[beeson]

Hey, Thanks alot for that Bugsy. I took a trip yesterday to Toronto and back (so mostly highway driving) which is about 220K round trip and I still averaged about 300 km (186.5 miles) on a tank, which is only about 17.6 miles/Gallon. It's funny you mentioned the temperature, because I monitored that the whole trip. I didn't realize that low temp would increase gas mileage until I read it somewhere yesterday. When I start the vehicle it seems that it gets up to normal temp but then it will drop shortly after to about 70-75. It seems to come up a bit if I'm not on the highway and I'm idling. Is it possible the thermostat is just sluggish in closing? I will replace it this week, I bought one with a gasket a while back because I had a small fluid leak but it turned out that it came from the water outlet elbow and not from the thermostat, so I never did replace it...sort of wish I had now.

As for the O2 Sensor...I've read alot about this and that it's a big contributor to fuel consumption but I find it hard to believe it's having problems since I passed the emissions test not even a month ago, AND I've had poor fuel consumption ever since I owned the car. But seriously, I'm not sure how I passed emissions anyway with that kind of gas mileage. Also, I have a chance to pick up a code reader for like $70 CAD at a local shop, would it be a wise idea to get that or would it likely not tell me anything? Thanks again brother, it's very much appreciated.

*forgot to mention the car has around 200k.

[Crasher]

Do you mean US or Imperial gallons? I think you use Imperial Gallons in Canada but I am not sure.

[beeson]

Hey Crasher, I did the conversion in US gallons. thanks.

[Crasher]

1 Imperial gallon is 1.2 US gallons so the figure will appear 20% worse to us than it is to you.