Wednesday, March 29, 2023


Ask Dave: Is it true that dish detergent is bad for RV sidewalls?

Dear Dave,
I’ve heard that dish soaps can dull the fiberglass gel coat finish of an RV, precisely because it’s strong enough to cut grease, so a good car wash product should be used instead to clean RV sidewalls. What are your thoughts on this? —Gary, 2014 Forest River rpod

Dear Gary,
I have been using dishwashing detergent to wash cars since 1973 and RVs since 1983. I have had no issue at all. Typically I use Dawn (blue), as it is environmentally friendly and does not contain any of the cleaning beads or particles you sometimes find in detergents. Remember, it was soft enough for the birds and wildlife after the oil spill in Alaska. More important is to use the proper micro towel, horse hair brush or other soft cleaning device.

Crane Composites, the company that makes Filon, Kemlite, and other fiberbglass FRP (fiberglass reinforced plastic) sidewall materials, also recommends a mild detergent and water. Keep in mind, the outermost component in your sidewall is a clear gelcoat that is not affected by the degreasing properties of the detergent as long as it does not have the “grit” of scrubbers in it.

However, I did some research with body shops and other paint experts. Most of them discourage using dish soap on an automotive finish as it can weaken the soft wax that is an aftermarket application. So, if you wax the sidewalls of your rig, could it deteriorate the protective wax covering? Maybe, but not right away. As I mentioned earlier, I have been using it for a long time. I worked in a full-service gas station all through high school and college, and even owned one for 3 years, and washed a ton of cars.

Detergent can dry out rubber and plastic

One other point that came up was detergent can dry out rubber and plastic. I had experienced that, so I have always been careful to treat the seals and any rubber/plastic components with 303 Protectant to reduce UV degradation.

I do find it ironic that the majority of posts and videos that state to NOT use dish detergent are companies that just so happen to sell a car washing product! One of the videos by Summit Racing stated that dish detergent is like liquid sandpaper. It said you can tell the difference between the gritty feeling on your fingers versus the smooth feel of the lubrications in their car wash foam. I was not able to find their product locally. However, I did purchase a car wash foam from the local parts store and I could not tell the difference between Dawn and their product. What I did notice is the Dawn seemed to be more concentrated and I needed less in my bucket to get a desired foam.

So, I go back to Crane Composites and their recommendation of a mild detergent. They even recommend Meguiar’s #56 Boat and RV Wax. So if you use a good wax, I doubt you will see any scratches or degradation in the finish.

Let’s see what our readers use for their rigs. I’m staying with Dawn (a Tony Orlando reference?).

Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club.

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9 months ago

I use regular car wash on our travel trailer to avoid removing the wax. Meguiar’s 56 Carnauba Wax is pretty amazing.

9 months ago

I use either Dawn or a Car Wash Cleaner. I protect everything, roof, seals and slides with 303. TT is 2017 and am always getting comments it looks like new.

9 months ago
Reply to  travelingjw

Do you use 303 instead of wax?

Phil Strong
9 months ago

In my 7 years of owning and caring for my 2014 Breeze I have found the most effective shampoo for my clear coat finish to be RainX Car Wash (eliminates spotting). I originally tried Tiffin’s recommendation of baby shampoo with very poor results. I protect my finish with McGuire’s Synthetic Sealant 2.0 Mirror Glaze. I have been told never to wax clear coat.

9 months ago

Tiffin recommends baby shampoo and vinegar for a wash on their products. For any RV that has full-body paint, it’s the paint that is the outer surface of the RV, not the fiberglass. For an automobile, you wouldn’t ask the steel company to recommend to wash it. Ask the paint manufacturer what to use, just like on an automobile.

9 months ago
Reply to  Michael

So does Newmar

9 months ago
Reply to  Michael

I agree with Michael. Baby shampoo and vinegar.

Bob M
9 months ago

I use Turtle Wax Max-Power car wash to wash my travel trailer. I’ve heard dishwashing soap will remove the wax. I use Meguiar’s Marine/RV M56 Pure Wax Carnauba Blend to wax my travel trailer. If I run short, I finish with Meguiar’s Ultimate paste wax.

Diane Tricomi
9 months ago

I see no problem with using Dawn on my RV. You just have to remember a little goes a long way, I have been using dawn for 6 years on my Travel trailer with waxing two times a year,

9 months ago

Using Dawn mixed to the proper concentration will not harm the finish. It will remove the wax though. I have an Alpha systems TPO roof on my TT. They recommend using a mild dish detergent for cleaning, and hosing down the sidewalls to prevent streaking.

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