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Discussion Starter #1
I know my car is not very good with gas by design, but it's getting worse lately. Over the summer I managed to hit up to 483km (around 28MPG US) with 30/70 highway/city. Then when Fall season hit I suddenly dropped to just barely above 400km (about 24.5MPG US) with the same city highway ratio. I know the cold weather hit my mileage in a major way but that is still pretty good considering I drive more in the city rush hour. I always use Shell gas but now my mother borrowed my car for a week and she filled it up with gas from Petro-Canada. Now I just got home from work and I already used up 1/4 tank (it's just a 40km round trip)! So clearly, the mileage is much worse in this latest tank. It's really annoying that this car sucks gas like it's nothing ...

In terms of driving, I drive smoothly (rpm below 2000rpm as much as possible), just had an oil change a few weeks ago, air filter is still clean, tire pressure is in spec. I dont know anymore, since September hit my mileage has been getting worse and worse ... now this Petro-Canada gas might be a factor too and it got cold here in Canada quite fast in September and the gas stations might have switched to their "winter" gas. Anyone else having this? Are there anything else I can do to improve this abysmal fuel economy?
 

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There are a couple things you should try, Might be a good idea to change your spark plugs. If you can get some Lucas fuel treatment toss some of that in there It should help clean out the fuel system. Also we are getting to that time of the year where places are switching to their winter gas which makes our gas mileage suffer. Also what kind of oil are you running? Synthetic or non synthetic.
 

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Discussion Starter #3
I'm actually going to check the spark plugs today. Come to think of it, the spark plugs havent been replaced for at least 2 years ... the car was a hand me down. I already did a fuel treatment a few weeks ago so I dont wanna do that again, it's bad to overdo those things.

Ya, the gas prices here in Toronto have dropped significantly lately and that's partially due to their switch to the "winter" gas. As for the oil, I just had an oil change and I use synthetic oil only.
 

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Fuel filter ASAP
 

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Discussion Starter #5
Thanks, the fuel filter is also new. Replaced just 4 months ago. I'm still on the same tank of gas actually and the fuel economy has actually gone back to "normal" more or less. I only used up a little less than 1/8 of a tank for the same distance (40km). I still don't know why I sometimes I get freaky gas mileage (burning fuel at a ridiculously high rate) then going back to normal the following day ...
 

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Discussion Starter #7
Really? Logically speaking, that may explain the random excessive fuel consumption. I didn't knw fuel injectors can get stuck open.
 

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Ive seen really random shit, I work at an autoparts store and this guy came in the other week where the dealership figured out that the one fuel injector was occasionally getting stuck open. Didn't happen all the time but it did sometimes. Id do some more research though first.
 

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Discussion Starter #9
Ya seems weird but oh well. Gas mileage still sucks currently but it's gotten better than my first 1/4 tank. Spark plugs are gonna be checked and MAF sensor will be cleaned out. Just waiting to get some time in my hands. I kinda suspect the gas that my mom put in it when she borrowed it. It was Petro-Canada, I've always used Shell gas and almost always had normal to good mileage with it. Just gonna burn this tank to empty and re-fill with my usual Shell and see what happens :D
 

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Any exhaust leaks? Have the O2 sensors been replaced recently?
 

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Discussion Starter #11
Exaust seems fine. Didn't get the chance to check the O2 sensors but my mechanic brother diagnosed it and the two sensors seem to operate normally. He says that the car is no timed properly. When he diagnoses it using his OBII device, he sees the car has an ignition timing of over 30 degrees from top dead center and that's when the car is in idle (parked not moving) and he says it should be much lower than that. Anyway, he did a vacuum test too and the engine is good. Sprayed the MAF sensor cleaner stuff too and the car did feel more responsive and better at acceleration, can't say anything about the mileage yet though
 
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