I recently installed a Purolator brand air filter in my 2003 2.5i. It seems my mileage has dropped at least 2 MPG. Any ideas? Thanks
Air Filter Brands
- Thread starter B & Js Z
- Start date
i dunno how a new filter can degrade your mileage...are you sure it's not your driving habit? 2.5 gets terrible gas mileage for what it is. i get 28mpg MAX on the highway down hilll with tail wind lol
Could it be that the air filter is more restrictive? Generally speaking, if many of the high flow filters advertise better performance/gas mileage then a more restrictive filter should reduce performance/gas mileage; If my reasoning is valid. And yes, I do recognize that there may be some execptions and special circumstances.B & Js Z said:
Yes that is my thinking too but what is a good high flow brand?
It's hard to beat the oem air filter for combined flow, protection, and price for a street driven car. Some filters may offer better flow at the cost of passing larger particulates (= increased wear) while others may offer equal or greater protection at a cost of reduced flow. Wet filters have an associated risk of MAF contamination. Most aftermarket filters have a lot of advertising hype and cost to go with the product, so it is difficult to know exactly what your getting. There are a few good articles floating around that do a good scientific comparison of a limited number of filters, IIRC there is one dealing with diesel air filters that is great.B & Js Z said:
Stick with the oem filter and you've spent your money wisely. You know what your getting and you have a good balance of performance and protection at a reasonalbe price. A popular mod with the oem filters is to remove the carbon secondary filter from the main paper element. My understanding is that in the US it's required for the pollution control system while the European cars do not have it. I don't know if there is really any added performance benefit, but the philosophy of less is better appears to be the standard for this. Keep in mind that alterations/modifications to the intake system may void your warranty and/or violate pollution control laws. My $0.02 on the subject. Caveat emptor!
FirstKnight
Member
Speaking of air panel filters...I don't know if anyone remembers a few years ago on the old Z4-UM site a company in the USA was selling air filters to Forum Members that were supposed to be very good; I bought one and never used it! It is still wrapped in original plastic in my garage! 
I recall them being quite sought after at one point. I wonder if they were all they were cracked up to be?
I recall them being quite sought after at one point. I wonder if they were all they were cracked up to be?FirstKnight said:Speaking of air panel filters...I don't know if anyone remembers a few years ago on the old Z4-UM site a company in the USA was selling air filters to Forum Members that were supposed to be very good; I bought one and never used it! It is still wrapped in original plastic in my garage!
If you're talking about the Streamline air filter, then yes it's the best one for the Z4 in the market.
FirstKnight
Member
GP20 said:FirstKnight said:Speaking of air panel filters...I don't know if anyone remembers a few years ago on the old Z4-UM site a company in the USA was selling air filters to Forum Members that were supposed to be very good; I bought one and never used it! It is still wrapped in original plastic in my garage!
If you're talking about the Streamline air filter, then yes it's the best one for the Z4 in the market.
That's the one! Yes, I have one of those. Not that I can use it anymore as it doubtless won't fit my Z4M.
