An air filter after 30-40k miles

[chris82]

This is after 30-40k miles in my 128i. I definitely think it needed changing. Replaced it with a Mann filter.

[Iron Man]

Originally Posted by chris82

This is after 30-40k miles in my 128i. I definitely think it needed changing. Replaced it with a Mann filter.

Sorry to bring an old thread back from the dead, but my car just hit 30,000 miles and the dealer said they won't change the filter until 45,000 miles.

While I have never went that long on any vehicle I've owned, your posting shows me that even after 30-40,000 miles the air filter can look pretty damn good.

I don't think this looks bad at all and hope mine looks like that. The air filter actually becomes more efficient as you use it, so some build up is expected and a good thing.

[andysantoro]

I had never heard that about air filters becoming more efficient after use. And I think that service interval is long. I have seen much shorter ones.

[6MT_Addict]

Originally Posted by andysantoro

I had never heard that about air filters becoming more efficient after use. And I think that service interval is long. I have seen much shorter ones.

+1.

They aren't expensive, especially buying off amazon or Rock Auto, IMO new filters every 10,000 or so is cheap insurance. Keep in mind though that if you do want to extend its life, periodically clean the filter. Remove it, and blow out with compressed air in the opposite direction air normally flows - i.e. Engine side to atmosphere side. Blowing the other way will just embed dirt into the filter

[Mr Rooty Von Tooty]

A less than perfectly clean air filter isn't a problem, because the mass airflow sensor accurately measure the volume of air entering the engine and signals the engine's computer the exact amount of fuel to add. The result is the filter has a longer lifetime before it has to be replaced.

The same is true for engine oil and some other items. The BMW engine could easily operate on 4 qts of oil in the pan, but its capacity is 7 qts. This extra margin of oil allows longer drain intervals. Using a synthetic oil also allow a longer service interval. Changing oil at 3K and 5K intervals is a waste of money and a precious resource.

Auto makers are very concerned with the cost of service to its owners and itself, so they want as long as possible service intervals. Some companies have 15K miles and 2 year intervals.

[Iron Man]

Originally Posted by andysantoro

I had never heard that about air filters becoming more efficient after use. And I think that service interval is long. I have seen much shorter ones.

Please see link and excerpt below.

http://www.fueleconomy.gov/feg/pdfs/...02_26_2009.pdf

2.3 DEFINING A CLOGGED AIR FILTER
The results of the testing of these air filter indicators agreed with the information found in the literature as to what the definition of a clogged air filter is in engineering terms. The function and design of intake air filters must address the following.

1. Engine durability
2. Filtration
3. Flow management
4. Pressure or head loss constraints
5. Overall noise, vibration, and harshness standards
6. Service requirements
7. Packaging
8. Styling/appearance
9. Emissions

All of these functions are to be met for the service life of the filter without allowing engine performance to be affected. In light- and medium-duty applications, the service life is normally defined by accumulated mileage. However, it is very common for over-servicing to occur in these applications due to a lack of understanding of how optimum air filter efficiency is achieved. The standard recommended service life for an air filter in light- and medium-duty applications, during normal driving conditions, is about 30,000 miles. It is common, however, for servicing to occur when the filter appears dirty. Engine air filters are designed to actually increase their efficiency by using this initial layer of dust as an added filter layer. Initial filter efficiency is usually approximately 98% but increases to more than 99% by the end of the service life of the filter. Therefore, changing an air filter before the useful service life is achieved can result in premature engine wear.