fuel economy

[Takimo]

So i went to the garage yesterday, and my mecanic told me i have a oil leak on my valve cover gasket, but i forgot to ask him if this can be related to my high gas consumption, i remember when i got the car 5 year ago it was around 17l/100km... now its around 22l/100km (i do almost city, no heavy foot), i just replace my air filter a week ago, my spark plug was change 5 year ago(now maybe they are sunk with oil and it doesnt help).... no rough idle, no giveaway sign of missfire, no code triggered... what can cause the extreme high fuel consumption ?

[alberniken]

Originally Posted by Takimo

So i went to the garage yesterday, and my mecanic told me i have a oil leak on my valve cover gasket, but i forgot to ask him if this can be related to my high gas consumption, i remember when i got the car 5 year ago it was around 17l/100km... now its around 22l/100km (i do almost city, no heavy foot), i just replace my air filter a week ago, my spark plug was change 5 year ago(now maybe they are sunk with oil and it doesnt help).... no rough idle, no giveaway sign of missfire, no code triggered... what can cause the extreme high fuel consumption ?

You seem to have had a problem for a while; I have a 2001 running KO2 tires (not good for fuel economy) and my commute is 200km of gravel road. I drive somewhat aggressive, and I average better than 14l/100k


Seems your O2 sensors may be off enough to run rich, but not enough to trigger engine light. If that is case, then your cat-converters might be getting plugged up. Had that happen on a Lexus RX300 after a year of running just a bit rich.


Bon chance,
K

[Takimo]

oh well i thought the x5 average is around 17l/100km sound like im in deep trouble

[alberniken]

Originally Posted by Takimo

oh well i thought the x5 average is around 17l/100km sound like im in deep trouble

Maybe I am just lucky, but I have to drive it very aggressively to burn fuel like that. My Suburban 4x4 can touch 17l/100k.


Hope it works out for you.
cheers
Ken

[Takimo]

how likely it would be the o2 sensor and how many they are in the x5 ?

[alberniken]

Originally Posted by Takimo

how likely it would be the o2 sensor and how many they are in the x5 ?

There are 4 O2 sensors, a set of GOOD ones will likely cost $300-$400. I have bought a complete set at Amazon.ca for a lot less, but those are of so-so quality. I do all my own work on items like that, so if they go bad it is only a bit of my time. If you are paying a mechanic, you might want to use the Bosch brand sensors. Also check to make sure your cats are not plugged up. They are VERY expensive to replace. Or you could just replace them with pipes (cat delete). This would trigger your check engine light permanently though.


I don't know about your mechanic, but if he is not really familiar with BMWs you will be paying a lot for his tuition.



If he is knowledgeable about BMW's, he should already have the proper test gear to confirm the sensors.



With an X5 of this age, if you cannot do a lot of the small jobs yourself, its going to become a very expensive car very quickly. Might be time to trade up.


I know this isn't truly helpful, but the the truth is that an X5 is not for someone on a tight budget.


Good luck
K

[andrewwynn]

o2: use Bosch. I used "German" copies I just had to eventually get Bosch all four.

Plugs: use OEM only. If you didnt change them.

Clean injectors: run some injector cleaner every 8000km or so. At least when you change oil.

Winter blend gas kills consumption. If you use ethanol blend gas like most of USA it'll kill your consumption.

Lastly: mix is determined from fuel pressure, math, injector pulse and mass air flow. You are likely due for MAF replacement, I know I'm overdue.

[Takimo]

okie dokie

[andrewwynn]

Follow up: I've been getting lean errors repeatedly, and it just dawned me long time since injector cleaner.



Highest highway mpg in months and the error didn't come back yet.

[Happy]