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1996 Subaru Legacy needs rustproofing in PA?

I just moved from Livingston, Montana (near Yellowstone! Yes, I’ve dodged a few bison over the years!), to northeastern Pennsylvania. It’s pretty wet here, I hear they salt the roads, and my car has always been out west. Do I need to get my dowager Subie some rustproof undercoating? (And btw, she made the 2,200 mile road trip like a champ!)

I would say no to rustproofing . All you will do at this point is cover up the grime and surface rust you already have. Others may disagree but that is my opinion.

Agree, it is FAR too late to add rust-proofing.

Too late at this point, as @Mustangman states.

I think that unless a vehicle has less than 500 miles on it, rustproofing will have no effect.

After 500 miles there is no way to clean the road grime and especially…salt from the nooks and crannies prior to any rustproofing is applied.
You can have it done, and any shop that does apply rust proofing will be happy to take your money. But that would be throwing money out the window. Just send it to me, I could use a little more money.


I concur that it is far too late for any type of undercoating or rustproofing.
By applying coatings to the underside of the car at this point, you would be sealing-in the grime and salt that are already there, and that could actually make things worse.

The best solution (no pun intended) would be to have the underbody washed-off after every heavy snowfall period.

As a cheapskate myself, I appreciate all the replies. I’ve lived in the western U.S. for more than 30 years, where rustproofing is unheard of, so didn’t know much about it. My old Subie has 238,000 miles on her, and I’m hoping to take her to 300K, despite the higher moisture content of NE Pennsylvania. Thanks, car people.

What about spraying oil on underbody, door bottoms, etc?

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At 238,000 miles I bet it’ll die from something else before rust becomes an issue.


I know people do that but I don’t like it. We have enough stuff getting into our ground water as it is.


Just like other rust preventative treatments, doing this is going to cover up any dirt and debris on the undercarriage. IMO, it is too late for this treatment as well, and for the same reasons. Unless the car is rusted already, it will take several years until the body rusts so badly that the car will be beyond use. It could easily take until at least 300,000 miles.

I’ve heard that undercoating can block drain holes that the manufacturer intended to be open, which would be a very bad thing to do.

Although there’s some debate on this, I prefer to underwash my car regularly in winter. Luckily, my favorite touch-free car wash claims not to use recycled water, which presumably might have some salt content in it.

I wouldn’t even fill the tank beyond half in a 23 year old Subaru. Save your money.

Be sure to wax the paint or every scratch will rust in a few months. Not true. Most people wax their cars but if you took an unwaxed old pickup to Maine from South Dakota you might experience the dreaded rust. The floor pans usually rust off some old Toyota cars in Maine but it only costs about $1,700 to get it fixed.