[tetsuo111]

Any suggestions for keeping the rear of the car cleaner, longer?

The rear window and tailgate on my E91 get dirty and dusty at the drop of a hat. My car color is dark Deep Sea Blue Metallic, and dirt is very visible over the dark color. The other surfaces on the car are almost spotless - the roof, hood and side panels shine. This indicates that the car is aerodynamic (Cd = 0.30) other than the low-pressure, turbulent flow "bubble" trailing the car.

Mine gets dirty almost immediately after a wash.

The old Detroit wagons used to use a wind deflector that looks similar to a spoiler but channels airflow from over the roof and redirects it down over the rear window. They generally worked well but are no longer used due to increased drag.

This picture is extreme, after returning from the mountains in the winter, but illustrates the extent of the problem - clean top and sides, filthy back. Thanks.

[tetsuo111]

Updating for the benefit of future searchers.

I applied RainX in two coats on the rear window. The weather is uncharacteristically dry this week so not the most challenging of conditions. Dust and dirt still collect in the rear. But the layer is very light and almost falls off the glass with a light swiffer brush.

Will update after a trip to the mountains if anything significant changes

[Torgus]

Originally Posted by tetsuo111

Updating for the benefit of future searchers.

I applied RainX in two coats on the rear window. The weather is uncharacteristically dry this week so not the most challenging of conditions. Dust and dirt still collect in the rear. But the layer is very light and almost falls off the glass with a light swiffer brush.

Will update after a trip to the mountains if anything significant changes

Thanks for the info. I used stupid amount of fluid keeping my back window clean on my ride into work. RainX isn't a bad idea.

[tetsuo111]

Originally Posted by Torgus

Thanks for the info. I used stupid amount of fluid keeping my back window clean on my ride into work. RainX isn't a bad idea.

Sadly I need to report the RainX helps, but doesn't fix, the dirty rear E91 problem. It's been a wet last week, and the entire car stays mostly clean other than the back. I began wiping down the glass, door, and bumper when I get home to keep things acceptable. This is not preferred solution.....

I wonder if these would help? Notice the vertical fairings on either side of the new X5 rear windor. Mercedes and Toyota are using these more frequently now on their new models.