That's overkill for washing your car.
The Clear Inline Hose Filter Canister has two cartridge options:
Water Softener Filter Cartridge (not included) – This cartridge neutralizes calcium and magnesium in the water, thereby eliminating hard water. Your car shampoo will lather better and your vehicle will be free of those nasty water spots. This cartridge can be renewed and reused indefinitely.
A water softener works by replacing the calcium and magnesium ions with sodium ions. Sodium ions are “soft”. They don’t produce scale and they don’t stain. They change the actual texture of the water, making it feel “slippery”. This causes water to sheet off the vehicle more effectively. Water that remains on the vehicle will not leave spots.
Sediment Filter Cartridge (not included) – This cartridge is made of 25 micron spun poly. It traps fine sediment as the water passes through so that nothing hits your vehicle but pure water. If you don’t have a hard water problem, this cartridge is all you need.
They are overselling the water softener aspect. If you really do have hard water, your house will already have a water softener unit. As to changing the "texture" of the water, that a bit of bullshit marketing; same with "foaming" - foaming has no impact on the efficacy of soap (see: Washing machines and dishwashers). It's just a hand feel thing (aka, marketing). And, if you dry your car (chamois) by hand vs just letting the water evaporate, you're not going to have water spot issues.
Filtering sediment? Again, if your house water has this problem, you have bigger problems than what you are washing your car with (like your dishwasher, shower heads will all clog up, not to mention water lines collecting sediment). Oh, and don't forget the dirt that is ALREADY on the car. That doesn't magically disappear...until you wash it.
If you really must, then do what Kennith says, go to the grocery store, buy 10 gallons of distilled water and wash your car with that.