muttleyturbo

iTrader: (5)

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bonesetter

iTrader: (9)

The old style thick black underseal does indeed get moisture behind it and actually can make corrosion worse

JDM's (especially super fun V3/4 Type R's ) have less corrosion protection, so need treating

I'm about to underseal my Type R - steam clean, leave for a few dry/hot days, then waxoyl spray with compressor on a ramp. Use about a gallon.

Waxoyl also stays transparent so you can always see what's going on. Treat any surface rust prior to application

mike80

I would treat any import as soon as its in the country, once the rust starts its very hard to stop and it will still rust behind the underseal as i know to my cost with previous cars.

No mistakes with my present car which is rust free, i had it booked into a garage to be cleaned then left to dry and undersealed on a warm day in summer with no moisture present, now's the time to do it.

Wooffy

Traditional underseal is a waste of time and also makes working under the car a fithy horrible job. Plus it dries out cracks and harbours water behind itself accelerating rust.

Best option is to use waxoyl (the clear variety not the black stuff)