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E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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  #1  
Old 07-27-2008, 08:26 AM
Solo1 Solo1 is offline
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Another MPG /Vanos / MAF discussion thread

Hi Folks

For 1.5 years, I have been trying to solve what I perceive to be a low MPG issue (see below). I drive a well maintained, 110k miled, 1998 528i Auto with a 2/98 build date.

I am trying to decide if an MAF and or Vanos replacement would now be a worthwhile investment in addition to all the expense I have already incurred. Unfortunately, I cannot use the Hyundai Sonata MAF part because I have the early 528i.

I have done all known maintenance items and mpg improvement methods discussed on the board except clean or replace the MAF and Vanos. I have no notable problems with MAF or Vanos and all engine codes are clear.

I think, however, that my mileage should be better, though I fear that the testaments to higher MPG after MAF and Vanos replacement may be, largely, a placebo effect, especially for the older single Vanos 528's.

Certainly, the statements are estimates of improvements and not done under 'apples to apples' comparisons. Does anyone have access to any good objective (more scientific)before and after MAF replacement data?

With automatic and A/C and not heavy footed driving in Orlando on flat roads I get the following mileage.

1) 14.7 mpg for the 3 mile commute downtown, traffic lights, traffic and stop signs, car not warmed up.

2) 17 - 18 MPG driving around town when not having to stop every mile for a traffic or stop light.

3) 27 MPG all highway, limited traffic with A/C and cruise control engaged.

I think all of the above should be 2-3 mpg higher. But, am hesitant to sond the money for MAF and VAnos without better confidence in improved performance. Nothing has worked so far!

Thoughts anyone?

Thanks in advance!
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  #2  
Old 07-27-2008, 12:56 PM
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528iKerb 528iKerb is offline
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Same exact issues as you, I'm at 160k. I am going to go ahead and replace the Vanos, MAF, and O2 sensors because of what I've been reading around here. I have also changed my fuel filter and had a pretty good increase in MPG and throttle response, but after driving another 528, I know mine has some significant issues that the 3 things above might fix.
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  #3  
Old 07-27-2008, 01:25 PM
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you defenetly have mileage problems, my 540i does slightly better than that in the city, I havent tested it on the highway enough to know though.
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  #4  
Old 07-27-2008, 02:10 PM
gp87210 gp87210 is offline
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Quote:
Originally Posted by Solo1 View Post
I have done all known maintenance items and mpg improvement methods discussed on the board except clean or replace the MAF and Vanos.
Cleaning the MAF is about as simple as it can get, so try that first.
The shop I took my 540 to did a GT1 scan and was able to confirm a bad MAF as the air flow reading was out of spec. I would have that checked first before I spend the money on a new MAF.
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Last edited by gp87210; 07-27-2008 at 02:14 PM.
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  #5  
Old 07-27-2008, 02:17 PM
Solo1 Solo1 is offline
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thank you for the reply. It seems idling at stop lights REALLY eats up the average MPG.

I'll have to have that checked out!

Thanks.
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  #6  
Old 07-27-2008, 05:05 PM
NNY528i NNY528i is offline
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Actually those numbers look about normal for what this car will do. It is very hard to compare one car to another because there are a lot of variables. For example you are in Orlando which me ans your AC is working overtime, compared to the guy from Massachusetts who is using his but its not working like crazy. You will get less mileage than him no matter what. I get less miles on the free way because I live in upstate NY and we have a vertical component to our roads that you Florida guys don't. I think your mileage is just about spot on the mark for what you can expect from a 98 528.
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  #7  
Old 07-27-2008, 05:32 PM
Solo1 Solo1 is offline
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Thanks for your reply. A few others have indicated the same thing. That is why I provided all the variables knowing that this is the only way to get a decent apples to apples comparison. People state their mileage , but usually don't provide the important details.

I mostly see people indicating mileage for 528's, 530's and 540's in the city well over 20 MPG and over 30 on the highway. My miles are way below that to an extent that it seems would not be accounted for by using A/C and having an auto transmission. I usually think they may be just reporting for segments of their travel where the MPG is higher.

So hard to decipher.
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Last edited by Solo1; 07-27-2008 at 07:18 PM.
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  #8  
Old 07-28-2008, 10:42 AM
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TimeOut TimeOut is offline
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I was in the same boat as you. No matter what I do, I can't get more than 17.5 MPG in my commute. Highway MPG seems fine. I got close to 28 MPG during a 3 hours trip a couple of weeks ago.

I replaced the MAF and pre-cat oxygen sensors before that trip. The overall MPG improvement is so marginal, it doesn't justify the money I paid for.
But, my car has only 61K miles so, I think these original parts were still in good shape. Yours with 110K miles could be different story though.

If I was you, I would just clean the MAF and maybe replace the two pre-cat oxygen sensors if you haven't done that already because, they should be replaced at 100K miles anyway. I would also replace the fuel filter.
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  #9  
Old 07-28-2008, 10:46 AM
Solo1 Solo1 is offline
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Thanks much for the reply.

Cleaning MAF does seem to be safer step. Many are reporting limited if any effects with replacemennt, yet my car is, as you said, higher mileage.

As I indicated, to no avail everything else has been done in attempt to improve mileage, except for MAF and Vanos replacement.
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  #10  
Old 07-28-2008, 11:20 AM
NNY528i NNY528i is offline
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Quote:
Originally Posted by Solo1 View Post
Thanks for your reply. A few others have indicated the same thing. That is why I provided all the variables knowing that this is the only way to get a decent apples to apples comparison. People state their mileage , but usually don't provide the important details.

I mostly see people indicating mileage for 528's, 530's and 540's in the city well over 20 MPG and over 30 on the highway. My miles are way below that to an extent that it seems would not be accounted for by using A/C and having an auto transmission. I usually think they may be just reporting for segments of their travel where the MPG is higher.

So hard to decipher.
Where are you seeing these reports?

Most people seem to be reporting high teens to low twenties for city and mid to high 20s for highway. I would guess there are less than 5 people who have stated they got over 30 ever and those tend to be out in the midwest where there are no turns and no hills.

Also few of these people are verifying actual mileage by the tank and ODO method, many just read the OBC which is normally a little high, even accounting for that you are basing your assumptions on some erroneous information.
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  #11  
Old 07-28-2008, 11:32 AM
Solo1 Solo1 is offline
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i've read alot of the mpg threads in Bimmerfest and Forums. As I said, I see alot of low 20's city and high 20's to low 30's highway.

My OBC is about .75 mpg high versus the old fashioned way of calculating mileage.
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Last edited by Solo1; 07-28-2008 at 11:34 AM.
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