Disgusting Gas Mileage

Alright, when I first got my car in 98, I was getting around 500 km to a tank of gas (450 if I did mostly city driving). Over a year, I noticed that it dropped by about 30 km a tank. Last summer, I put my CAI (AEM). Now this will sound weird, but my gas mileage actually decreased. I was getting about 430 km to a tank (not all city driving).
I moved from Northern Alberta, to Halifax about four months ago, and my gas mileage decreased again! I was down to about 400 km a tank ( usually less). I tried reseting the ECU twice but it hasn’t made a difference. And that isn’t even the worst part. On this tank of gas, with mostly city driving, it looks like I’m going to get about 300 km! What the hell is going on? I’m going to check the air filter this weekend but that can’t possibly be the only reason why I’m losing so much mileage.
Here’s the details on my car: 1991 RS, AEM CAI, recent tune up (before I left Alberta), 135 000 kms. I also noticed that my car seems to produce a lot more exhaust than other vehicles. It’s not blue, but it does have a sweet odor to it. I also know that my car needs a valve adjustment.
(Also, if anyone knows of a good garage that I could take my car to in Halifax, I would appreciate the suggestion)

do you have auto trans ?

well I improved my gas milage… FINALLY!

this is what i did:

  1. replaced o2 sensor
  2. replaced plugs
  3. replaced wires
  4. oil change (greased lightning) & oil filter
  5. installed tstat (my car didn’t have one)
  6. coolant change/flush

I used to get like 100 miles to a tank which is 10 miles to a gallon, I don’t know how this converts to KMs, but this is horrible gas milage. I now should get like 25-30, I still haven’t finished my tank yet. I still haven’t reset my ECU, so my milage should increase even more, anyway, all of this will almost definetely improve your milage. The only thing left is fuel filter and pcv valve, my pcv valve is still good so I got a few miles left. Good Luck

Also, if your milage is decreasing regionally, some cheaper stations water down their gas, and also I found out that during the winter months gasoline is “oxygenated” further reducing the milage.

Romanz: thanx for the tips

x4evawizex: I’ll try all those things and post how they turned out.

Anyone have any ideas about that garage in Halifax?