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958 Cayenne DIY: Filling diesel exhaust fluid (DEF) tank


958 Cayenne DIY: Filling diesel exhaust fluid (DEF) tank

Old 10-05-2018, 03:29 PM
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Join Date: May 2016
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Default 958 Cayenne DIY: Filling diesel exhaust fluid (DEF) tank

This article discusses filling of the diesel exhaust fluid (DEF) tank. The diesel Cayenne uses a urea based exhaust fluid to reduce levels of NOx. Every engine oil change Porsche requires the top off of the DEF tank. DEF consumption depends on how you use your vehicle. The Cayenne will also start to warn you if the DEF tank level is getting low with about 600 miles of range left. Indeed to meet pollution standards the car will eventually not be able to be started if the tank is empty. The Cayenne DEF tank holds slightly more than 5 gallons. Heavy towing, etc will increase DEF consumption. My Cayenne in light duty uses 2 to 2.5 gallons of DEF every 5K miles even after the emission fix. Unlike some other VW cars the DEF filler is hidden under the spare tire making it slightly more of a hassle to top off.

DEF can be purchased at auto stores, Walmart, etc. AdBlue is a trade name for DEF. When purchasing DEF be sure to check date of manufacture so you are getting fresh DEF. DEF has a shelf life that can be as short as 6 months if not stored in a cool place. I've taken to keep mine inside my house much to the dismay of my wife.

To access the DEF fill port you'll have to open the rear deck lid over the spare tire. There is a cover in the body and underneath the cover is the actual screw on top to the DEF tank. I had to use an open end wrench to loosen the tank screw top. Here is a photo of the DEF tank in my car while being serviced at the dealer.

You can use a funnel and a flash light to see how full the tank is getting as you pour in the DEF. It may overflow out under the car. You'll want to cover the top of the bumper with an old towel so you don't spill any DEF on things and wear some gloves. The other fill method is to convert an Audi DEF container into a funnel by cutting the bottom out as shown below. The Audi DEF container nicely screws onto the DEF tank and has a check valve so you can fill the tank without much spillage. Any DEF spilled needs to be washed away or wiped up with a damp cloth.

To use the Audi DEF bottle you have to remove the spare tire while the funnel just slips in without having to remove the spare tire. YMMV. I cut the bottom out to make it into a funnel. The Audi DEF bottle P/N G 052 910 A2 holds Ż gallon and is about $16 from Amazon. The Audi bottle is nicer to travel with in the unlikely event you need to add DEF while on a road trip. Walmart DEF 2 Ż gallon container is under $10 and is shown below.
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