re: Best Car Wash Soap

McGuiere (or however you spell it) Gold.

If for no other reason, it is spelled Meguiar's. Yeah I know, that doesn't look right. Even spell check doesn't like it either.

Glad to be of service

Meguiars gold class is great stuff!

Buc-ee's car wash in Baytown, TX.

As mentioned you need to specify a bit more on what you're looking for. If you want to just get dirt off your car, Meguiar's and any cheap car shampoo will do the job. Car shampoo is meant so that it helps lift up dirt as you scrub it off with a mitt/brush easily without damaging the car. Most are pH neutral so that it doesn't affect your clear coat. There are shampoos that offer higher pH for wax removal and others that had "wash & wax" which will add a tiny bit more of a protective layer without putting in the time to wax your car.

Personally, I would go with Chemical Guys or Adam's. Any of their standard car shampoos will do fine. Add a foam cannon that can go on a garden hose and it'll help with the foam process. If you have a cheap pressure washer that goes below 2000 psi you can buy a foam cannon for better application. Get a chenille microfiber mitt and a good and large drying towel.

For wheels, get a spray cleaner and brush set specific to your wheel type (alloy/painted/chrome) and either a tire shine or the Chemical Guys VRP protectant. It works on interior and can work on tires/black plastic exterior. Buy a cheap set of applicators for that.

I am pretty brand loyal to Chemical Guys for their solutions, but I would say that their New Car Smell air freshener spray is the best smell on the planet for your vehicle.