Hey - i am coming up on a year with the 4runner and have enjoyed it so far. i have taken it wheeling almost every weekend. i had to look at about 4 trucks before finding one in decent shape rust-wise in the Northeast and i finally did. After one winter with it...i decided im going to POR15 this thing, as i do want it to last for many more years and figured id better get this out of the way. going to buy a quart at a time and do sections at a time over this summer. i still need to figure out if im going to replace the stock skids or treat the ones i have (one small hole in front skid.) i decided to do this after i just recently degreased the entire underside with a strong simple green solution - this project will be worth it where i live, and with the amount of money i have into this thing already with a few other decent mods id like to do as well.

just an FYI for ya: POR stands for paint over rust, its intended to be applied over rusty metal or properly cleaned & scuffed bare metal. lots of guys just slather it on everywhere, including over the existing factory coatings or previous paint.

it will go over those areas & hold up for awhile, but its only as strong as the surface its applied over. i would suggest being carefull where you apply it, use it for rusty areas or bare metal where you have sanded, scraped or blasted the paint off. then use a top coat of a good paint over it & the rest of the painted areas so it all matches color.

duly noted, thanks. i am going to get rid of some flaky areas and lightly skuff/wire wheel elsewhere. im sure there will be rust to POR, perhaps ill use some metal etching on other spots that look decent at the moment. i am contemplating using 3M underside spray for the area where my spare used to be (carrier on hatch now) and possibly the skids.

Whatever you do don't neglect the inside of the frame as often frames rust inside out. Something like spraying Fluid Film annually in all frame cavities will extend the life a huge amount. The surface rust on the outside is not usually a big issue, it's where salt and moisture sit like on concave areas, inside and any areas of the frame that can collect it. Ford's trucks like to rust on the inside where the gas tank stops the area from getting cleaned.

so since creating this post i have been under my truck with a 3m wirewheel,
and i came to the conclusion my frame and undercarriage dont merit POR15 yet...essentially i would need to etch everywhere, i dont have enough surface rust to paint over (what POR15 prefers) i thought about painting just the welds and spot painting, then spraying over, but it didnt add up.
truck is going to be getting all 6 cans of this instead. even though i live in NE my truck is garaged nightly and im glad i spent time finding one that was pretty clean.

that undercoating is going to give the rust a great environment to grow.