I've heard that it's good to wash your car with dish soap such as Dawn before you wax it in order to remove all the old wax. Is this true?

 

yeap it will strip and remove the previous wax..but dont over do it..it will also remove the clear coat if you go crazy with it

 

Well it depends on what kind of "wax" you are using really. For cars that don't require much prep work (like removing swirls or using paint cleaners) DAWN would suffice for removing old wax. It's generally recommended to use a dish liquid before using a paint sealant like Zaino, Klasse, etc...so that it can bond properly. If you're using a carnauba wax, I'd say it's best to use a separate paint cleaner to prep the car instead of a dish soap. A paint cleaner will be much more effective at removing all old wax, old paint, and some contamination. Plus a new coat of carnauba will work fine on top of "old" wax. This is not true if you try to apply a sealant over old wax....

You shouldn't make a habit of washing with dish liquids. When I had my Camaro for 8 years, I think I may have used dish liquid on it twice in that time to remove wax before using a sealant. Since dish liquids are a high alkaline solution it can weaken and dull the paint if used too often. Otherwise always use a car wash soap that is milder for use on paints.

 

It gets contaminants such as tar and sap off of the paint better than car wash soap but it's not "magical" and won't get everything off. If you want to remove your old wax that'd do the trick. It doesn't hurt your clear coat other than taking the wax off.

 

I would use it only on a heavilly oxidized old car before getting out the old rubbing compound. Never on clear coat paint. Polish will rough up the old wax good enough,

Its dish soap, it shoud stay in the kitchen with the dishes.