What shall I do with rusts underbody?

I am suffering from the same (rust in underbody). Here people used to get new cars treated but as car leasing got more popular and cars got better treated at factory already, that tradition faded. People don’t care anymore. Thats a pity.

My 2010 is mint from outside, not a spot anywhere. But the bottom.. I sprayed Dinitrol ML as much i could to try to slow it down. It has additives to slow rusting and it penetrates very well (very low viscocity, like wd40 before drying). It is actually for enclosures mainly and cannot resist mechanical wear too well but if one spray once every year it shall definately help. And its cheap stuff (some 5usd per 500ml bottle). And you can obviously spray to all enclosures, doors etc. These guys do have actual rust converters as well (RC900). Some use it but i’ve never tried because you need to spray something on top.



Once the rusting has started one definately should not package it by traditional thick&soft underbody coats. If some body shop offer full treatment for rusty 10year old car they are just after your money. Only way is to either clean it super well (bare spotless metal) and then have it properly coated or, start treating with these oily thin stuff regularly. Once or twice a year. Any oil is better than nothing. Even cooking oil but it does not last too many rainy days

@Mendel Leisk Your car underbody looks absolutely beautiful. I am jealous. Yours is one of the few that could actually benefit from full rust proofing. I would do it if car is planned to keep long

 

I've treated the underside a couple of times now. My strategy is to raise one end at a time, front or rear, put it on safety stands, take of the wheels at that end, and as many of the underbody plastic panels as needed. I used full-strength boiled linseed oil. I coated over suspension components that had rust starting, and that's (somewhat surprisingly) seemed to arrest the rust progress.

I think I'm done, at least for a few years. I'll just do a little touch up now, if I notice something new rusting, that I've previously missed.

To be fair, the car is garage stored (doesn't get dew-covered every morning), our winters are quite mild on the coast, and our usage is low as well.