Really depends on a number of things. Do you have any codes?
Things that can cause poor mileage include:
* Intake leaks
* Clogged fuel filter
* O2 sensors nearing or surpassing 100k
* Bad MAF
* Spark plugs / ignition coils (unlikely though)
* Clogged catalytic converter (this one is my issue)
And the most important one:
Non-fuel efficient driving (driving style)
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The winter fuel blend also result in fewer MPGs vs. summer blend. Nice that regular is $1.88 & premium $2.18 currently!
2006 330ci ZHP - Silbergrau Metallic / Stoff Laser/Anthrazit / Alu Black Cube trim / Adaptive Xenon headlights / HK hi-fi system / heated front seats
Yes, the O2 sensors are very sensitive pieces of equipment. They help with adjusting for air/fuel mixture.
My car has clogged cats, with a serious loss of power/torque and a huge hit on fuel economy. Where I used to be able to easily hit 30-31 mpg highway, before O2 sensor replacement I struggled to hit 24, and a Prius can out-accelerate my car. Acceleration also feels funky; sometimes it's a little choppy. Here is a video I took on accelerating on to an on-ramp. 3rd gear, 45 mph to almost 75 mph took that amount of time.
https://youtu.be/MH4jsI4EOFo
Replacing my O2 sensors allows me to at least maintain 25-26 mpg, even with the clogged cat.
It doesn't make that much of a difference with a well running vehicle, in my experience.
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No lights on dashboard so no codes that I’m aware of. Car drives fine and the same way since i got it so just confused as to what it could be. Turns out there are various reasons for it. I’m pretty sure previous owner did spark plugs but o2 sensors I believe are original.
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Which O2 sensors should be replaced? precat or post cat? Is it a pretty easy job?
~ 2005 330ci ZHP Silbergrau | Black cube | Leather ~
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Pre-cat. Yep it’s easy. They are right on top of the manifold
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