Around here, touchless carwashes like the one in the video below are quite common. I've used them on other cars with decent results. Essentially, it's a plastic tube with a bunch of nozzles that moves around the car. I'm assuming it uses some kind of a proximity sensor.

Have any of you put a G through this type of wash? I'm concerned that it may be unable to "see" the spare tire cover and hit it as a result.

 

We have one some like this locally here in KY and it works just fine.

 

There's one similar to this one in Park City, Utah. I run my G 63 through it all the time. I was slightly nervous the first 10 or 20 times, but no problems And, it does a surprisingly decent job.

 

I use a car wash like this every couple of weeks and have never had any issues.