I'm not sure if this will work for all E46 owners, but I increased my MPG from 20 to 25.5 by doing two things

i) taking the spare wheel out of the car.
ii) taking my girlfriend out of the car.

Weight Loss of the two items combined was enough to get my MPG shooting up.

 

Lol. I'm sure your woman was pleased.

All jokes aside; check the O2 sensors, they seem to be worn and are causing a loss of efficient consumption.

Good luck


Sent from my iPhone using BimmerApp

 

iight can someone be a better help

 

check your tire pressure, I filled my tires on my daily driver a couples of psi below the max. got me some more mpgs. Rides a little rougher but its just my work car so its cool

 

if you are approaching a red light from a good distance, just free ride it to the light, chances are it will turn green by the time you approach the light without coming to a halt and accelerating off.

 

tire pressure and spark plugs.

A/C and windows up after 40mph. no A/C and windows down less than 40mph.

gear oils changed to high grade synthetics helped some too.

 

A/C and windows up after 40mph. no A/C and windows down less than 40mph.

what does that mean?

 

Do you still have the original oxygen sensors at 120,000 miles? Fresh ones help.

 

Also, if you are going to do spark plugs (which helped me to improve my mileage a bit and improved response too), then you might as well clean the MAF sensor, replace the fuel filter, and if you haven't already, replace the air filter. Plus what all the other people said above...

 

Reduce the use of the biggest gas waster in your car... the brakes. Every time you get on the brakes some amount of gas is effectively going up in wasted heat. Watch traffic and signals way ahead and drive so as to miminize the need to use the brakes. Coasting to a stop and then accelerating (gently) away cost very little gas, but staying on the gas until you have to get on the brakes hard to stop is just throwing gas away.
I average 25 - 27 mpg in suburban driving and 32 - 33 on the interstates.

 

^ 27 city thats pretty good im usually 22mpg. i picked up my boy at laguardia about 90 mins away trying to get good mileage and i clocked 37mpg i couldnt believe it

 

using GOOD gas also improves millage. dont use regular!!

 

Funny...my last fillup on regular netted 31.9mpg. YMMV (pun)

 

You can buy a driver upgrade to get better mpg. An upgraded driver should get around 25mpg in city driving. The upgrade can be DIY'ed and will cost about 50% of your ego. But you can keep the AC on at full blow at all times to keep the bruised ego cool.

 

I have always thought spending money on things that are not part of maintenance was pointless, since you could spend that money on gas. The only thing that I have noticed that helps is changing ones driving style. Maybe instead of trying to save money on guess, cut out other needless spending in your life and use that for gas money. (not saying that you have any)

 

Switching over to using proper punctuation increased my mileage by at least 2-3 mpg.

 

Check those O2s

I bet the pre-cats could use some love.

 

Make sure:
- air and fuel filters are clean.
- plugs and wires are good.
- tire pressures is good.
- drive between 2500rpm and 3500rpm.

hope this helps.

 

I'd second the O2 sensors. It's possible for them to degrade enough to lower your mileage but still not throw a code.

Does anyone know of a good way to check O2 sensor functionality, besides the "if they're old, replace them" mantra?

 

My 2001 3251 wagon just runs 18mpg, about 20miles daily local drive, i think it's really bad with gas hits almost 4.35 a gallon now.

i do have po365 eroor code on, which is (i've heard from other posts) exhaust camshaft position sensor is bad. anyone know this sensor does affect mpg..??

how to improve mpg ..??

i forget to say my wagon just past 58k miles.....



thanks,

 

Driving habits are the single most effective thing you can change if you want to improve fuel economy. Slow down a bit, apex your corners, stay off the brakes, etc.


How well is the car maintained? Check for vacuum leaks, change your plugs, your fuel filter, O2 sensors, air filter, etc.


And then the mods, which I presume is what you were trying to get at. Headers may help a little, but not nearly as much as the two above mentioned categories.

 

mpg

I think my driving habit is not bad, i rarely rev over 3-3.5k rpm and i know how much you lose everytime you step on brake.


This morning, i spent awhile check all 6 spark plugs and i found most of them were wet of gas and oil ( i guess). I think this is why my fuel efficiency is so bad, too much gas were injected. i heard other thread was saying this type of plugs last at least 100k miles, mine just turn to 58k, so i brushed clean with steel brush and air down and put them back, i hope poor mpg is not from these plugs. I had changed air filter last summer when it has 52k and i double checked it was not dirty. I don't know about fuel filter, i may want to change it later. I dont know about O2 or vacuum leak. i dont get error code other than po365, also misfire

And i also checked exhaust camshaft sensor, it wasn't so hard to take out. I am getting one from

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?VISuperSize&item=120675610881

it's just 31.59 with o ring plus 8 dlls shipping, is this reliable one..??? price is not bad though...

I will post the result after i replace cps, I hope this is the main cause of poor mpg...

thx,

 

I think my driving habit is not bad, i rarely rev over 3-3.5k rpm and i know how much you lose everytime you step on brake.


This morning, i spent awhile check all 6 spark plugs and i found most of them were wet of gas and oil ( i guess). I think this is why my fuel efficiency is so bad, too much gas were injected. i heard other thread was saying this type of plugs last at least 100k miles, mine just turn to 58k, so i brushed clean with steel brush and air down and put them back, i hope poor mpg is not from these plugs. I had changed air filter last summer when it has 52k and i double checked it was not dirty. I don't know about fuel filter, i may want to change it later. I dont know about O2 or vacuum leak. i dont get error code other than po365, also misfire

And i also checked exhaust camshaft sensor, it wasn't so hard to take out. I am getting one from

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?VISuperSize&item=120675610881

it's just 31.59 with o ring plus 8 dlls shipping, is this reliable one..??? price is not bad though...

I will post the result after i replace cps, I hope this is the main cause of poor mpg...

thx,

You're running rich. Are all the trips you take short ones? EDIT: also, are you feathering the throttle until the engine is warm?

Check O2 sensor, keep the tires pumped to correct pressure, make sure your brakes aren't sticking, etc. Also, if you modified anything it wouldn't hurt to disconnect the battery so the computer can readjust to your driving style and any new parts.

I average 8.5L/100km (34mpg) in combined city/highway driving with the 325i. This is according to the onboard computer, which I have reset twice just in case it was lying to me

 

Mpg

THANKS YOUR HINT ON BRAKES,

I DID NOTICED A BURNING SMELL ON THE WHEELS AFTER ROUTINE DRIVE FROM OMY WORK ABOUT 10 MILES OR LESS. I HAD REPLACED REAR BRAKE PAD RECENTLY AND IT MIGHT BE ONE OF THE CAUSES....

AC_2007,

What do you mean by " feathering the throttle until the engine is warm" ???

I am about to buy CPS from

http://cgi.ebay.com/ebaymotors/ws/eB...m=120675610881

Does anyone knows this auto parts ebayer ??? or any other recommendations.....

I am appreciated....

:thumbsup:

 

THANKS YOUR HINT ON BRAKES,

I DID NOTICED A BURNING SMELL ON THE WHEELS AFTER ROUTINE DRIVE FROM OMY WORK ABOUT 10 MILES OR LESS. I HAD REPLACED REAR BRAKE PAD RECENTLY AND IT MIGHT BE ONE OF THE CAUSES....

AC_2007,

What do you mean by " feathering the throttle until the engine is warm" ???

I am about to buy CPS from

http://cgi.ebay.com/ebaymotors/ws/eB...m=120675610881

Does anyone knows this auto parts ebayer ??? or any other recommendations.....

I am appreciated....

:thumbsup:

My Honda winter car failed emissions because it had a sticking front caliper.. go figure

By feathering the throttle, I mean drive it gently and don't floor it, especially until the engine is warm.

 

Ok, i will double check the brakes this weekend, may get some lubs on....

Yes, i do drive slow even the engine is hot, i rarely rev over 3k rpm, so i think it's shouldn't be problem from my driving habit.....

Another question is, how to reset computer, so all error or records can be erased and i may drive a bran new car again... Is it possible...???

 

Disconnect battery, I explained why in my previous post..

 

I was averaging 24 city/highway when I first purchased the car with 5000 miles. I worst I've seen my mileage was 17mpg average. Since replacing a few things my mileage increase to 22mpg.

Things replaced that improved my mileage:

K&N trashed and replaced with OEM filter
Iridiums trashed and replaced with OEM plugs
CCV
fuel filter
lightweight flywheel

I believe my Cats and O2 sensors may be somewhat fouled by the CCV failure, but I have significantly improved my mileage by replacing some aftermarket crap with OEM.

 

My god how has nobody said this yet? REPOST. Search the forum, there's countless threads about this. In the end, driver determines mpg.

 

Just went through thread going back 2 years and saw no mention of thermostat.

Check its function. If engine is running cooler than it wants to, it will burn a lot more gas. If it dips any at all below dead center on temp gauge, replace it. Not saying this to OP, since I doubt he's here, but to anyone reading.

 

+1
my thermostat was stuck open and the car took a really long time to heat up, on my trip from LA to Vegas it couldn't get up to the middle...i still did get around 350+ miles on that tank of gas even by cruising at around 90 mph most of the way...

 

i like the idea about the thermostat... mine is stuck open it seems and it runs cool. I still average 26, but looking to replace it soon anyway.

XAVI - I agree about the iridiums, but I have ran many a k&n filters in my life and have one that I havent even installed yet. I am driving all week to make sure my MPG smooths out before installing it so I can determine the effect. Personally, I don't think the different air filter could have that big of an effect. Maybe I am missing something??

And REEZ - if you think ditching the girlfriend increases your MPG, you should see what ditching the WIFE does.

 

I am driving all week to make sure my MPG smooths out before installing it so I can determine the effect. Personally, I don't think the different air filter could have that big of an effect. Maybe I am missing something??

You might be missing that IF the K&N flows more air, your ECM will inject more fuel to compensate and keep the Air/Fuel ratio the same and decrease your mileage......