If you're driving in Canada where the roads have more salt than snow on them, you need rust proofing. It not only protects the bodies, which are more rust resistant on MBs than on other cars, but for all the other metal parts on the car from exhaust to water pump. I have my 1986 420SEL done every year. All the MB body shops in Toronto say Krown is the only one to use. You have to becareful because some of the rustproofers are incompatible with what MB already has put on the cars (rubberized undercoating, etc). I suggest you do it. It cost $100 per year and is pretty good insurance. If you get it every year Krown guarantees their work, meaning they replace or pay to have fixed parts that rust on you. Also, many people think it is an absolute must so when it comes time to sell if you can show the rust proofing receipts you may get a better price. If you plan to keep the car forever like me than rustproofing is an even bigger must.

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Jason Priest
1999 E430
1995 E420 - retired
1986 420SEL - retired