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Discussion Starter · #1 · (Edited)
Ok I have a 2001 bmw 325i sedan and it has 146,000 mile son it. What I notice from a stop and slowly giving it gas, around 1,500 to 2,000 rpm's I hear a hiss/ like air being pumped out or something from the engine area or intake and at that time the mpg gauge the ones that says 12, 15, 25, 35, so on so on go all the way to the right which starts with 12 mpg.

Anyone know why is this?

Now another issue is forgot to mention its the wifes car and we put regualr gas in it 87 octane and according to the heads up display reading it gets 17.9 miles per gallon, which i think is kind of accurate because just by looking at the gas tank gauge it goes down quite a bit for being a 6 banger small liter engine. I have a 05 6.0L pontiac gto GOAT which I do put in highest surpreme gas and thats about same as mine for city driving we do.

So today I pulled in to clean up a same year or give or take year off of my 01 325i was wagon model which it said like 25.0 miles per gallon form the reading.

Can bad 02 sensors and using 87 octane or vaccum leaks cause bad gas miealge for the bimmer?
 

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Sounds like maybe lower intake boot? Sounds like a similar problem I am having.
 

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Discussion Starter · #3 ·
Sounds like maybe lower intake boot? Sounds like a similar problem I am having.
So go out and into your car with radio off and windows up and from a stop barely taking off slowly see if you hear a hiss of air and notice the MPG gauge peg all the way to the right to the first number 12. thanks


I do have a check engine light that goes off and on randomly, and the last time I check with my cheapo scanne roff ebay for 30 bucks was a common forgot the number right now but the o2 sensors needs replaced, and then at rizzolis automotive mechanic sho where i work in santa maria, ca they did my freebie oil change month ago and the mechanic check for codes and said same thing 02 sensors are bad.

Now another issue is forgot to mention its the wifes car and we put regualr gas in it 87 octane and according to the heads up display reading it gets 17.9 miles per gallon, which i think is kind of accurate because just by looking at the gas tank gauge it goes down quite a bit for being a 6 banger small liter engine. I have a 05 6.0L pontiac gto GOAT which I do put in highest surpreme gas and thats about same as mine for city driving we do.

So today I pulled in to clean up a same year or give or take year off of my 01 325i was wagon model which it said like 25.0 miles per gallon form the reading.

Can bad 02 sensors and using 87 octane or vaccum leaks cause bad gas miealge for the bimmer?
 

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Mine isnt that severe. I think my tear is minimal because it wont make the hissing noise very often and only when accelerating. Not stationary. But yea, definitely a bad idea to put in 87. Our cars are meant to use only supreme and everyone recommend shell or chevron only. Putting 87 in leads to problems according to many. So that, plus bad O2 sensors will definitely lead to lower MPG. And I believe i read somewhere that intake boot does affect it some, just not sure to what degree.
 
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