Do you need underbody rust protection on new Prime?

Yes. You should NOT worry about it and save your money.

The things that you can SEE under the car that start to show rust are thick and solid enough that a little rust won't hurt anything; most of them, a LOT of rust won't hurt.

The places where rust might be a problem typically are not exposed to view AND thus can't easily be "treated" with any kind of additional product either.

ALL after-market rust treatments are a scam; some more than others.

 

Are you able to safely raise and support the car yourself? If so, I'd have a look, and don't be surprised if you're seeing extensive rust-bloom already. In particular: suspension components, bolts, welds. Toyota seems to have applied a cursory/cosmetic single coat of black paint on a lot of stuff, and no galvanizing or similar coatings.

Clean and apply a wax-oil spray, work it in with brush. Also, back out any small fasteners holding on plastic panels, drench them with with the same spray and reinstall. Not doing that, give it three~four years in the rust belt, and you'll be snapping the heads of those if you ever try to remove them.

Honda's a lot more diligent about rust protection, in my experience. Though to be fair, it could be some coatings have been outlawed of late??

 

Wether on the Prime or not, I use CRC Marine grade heavy duty rust inhibitor (about $12 bucks on eBay), used it on my 08' Gen 2 Prius to prevent any further corrosion since it was already two years old. Works well and in the very near future before whatever winter brings in Ohio will be putting the new Prius 2 up on the ramps and spraying anything that looks rust prone BEFORE any of the underside gets hit with the local brand of sand and salt mixture.

 

I had it done right away. Snow and ice and the chemicals they put down on the road is so hard on any car.

 

my 2004 is still rust free with no treatments.

 

But you only drive it north and south to church on Sundays.

 

true, but the northern salt is ferocious!

 

It's not known as the rust belt for nothin'.

At the other extreme, Japan doesn't salt roads. It is one of those resources they have to import, which makes it to valuable to just throw on the ground. This is why early cars from their makes had rust issues; they never had to contend with what road salt can do. I would have thought they have figured it out by now, but the Tacoma had periods with rust issues after its introduction.

 

A lot of the tubular frame vehicle owners would get rid of their used motor oil by spraying it on the inside of their tube frames for rust prevention. Gag, what a mess in so many ways.

 

My grandfather's neighbors were in construction, and they used that oil on the timber used for concrete molds.
Hell, when we had a gravel driveway, my father would just let it drain on the ground.

 

IIRC, I heard it's not good to put undercoating on a car that's been treated at the factory 'cause it can trap moisture in and just make things worse.

 

Those of us in California don't have to worry about road salt, either. Road salt is outlawed due to the impact on the environment (most plants really can't deal with salt). The only areas where salt could have been of use are high mountainous areas, which are sparsely populated (except by winter sport enthusiasts). They put down sand, require chains, and if that is not enough, they just close the road.

 

My 2004 Prius is also rust free, 224,000 miles.

 

my daughters '99 accord was a rust bucket.

 

Maybe they've outlawed certain (effective) rust preventing coatings since? Besides our 2010 Prius, I'm crawling under an 06 Civic and a 10 Pilot. Both seem a lot better preserved, and they are also seeing a lot more miles than our garage queen. That said the 06 Civic has one torsion bar that "didn't get the memo", is more or less pure rust now, failed.

 

Remember to consider location. Where my parents live in North Carolina, an inch of snow shuts everything down.

A question also arises, are the Civic and Pilot made in North America. Japan doesn't salt roads in the places that would need it, because they have to import the salt. Plant managers there might underestimate the value rust protection has to a car coming here, and might give a light coat for better numbers at the bottom line. There could also be the manufacturer difference.

 

Not sure about the Pilot, the Civic is an 06, the hybrid, made in Japan. It really seems like Honda's more dilligent, the heavy suspension members look near pristine, like everthing's galvanized or some very inert coating. Ditto for bolts. I am starting to see some rust, and there's some outliers (that torsion bar gone completely). Another miss: the Civic's AC condensor is terrible too, lower rows of fins starting to fall off, lol. Not leaking though. Yet...

I get the sense plants in the States vs Japan, they would not depart from specs on the whim of local plant managers, that everything is by the book. OTOH, the official spec's might be changed, country by country.

 

The A/C condenser is likely aluminum, and coatings could effect the efficiency of it doing its main job. With luck, its just the fins failing. They are thin, and the tubing has to be thick for the pressures.

I was leaning towards the brand difference. Small Toyota pick ups have a history of rust issues coming up. For the first one to NA markets, it was because of a lack of experience in a place that makes heavy use of salt in the winter. The truck's bed liner had some welded seems where salt can more easily start the rusting process. American makes were using stamped metal liners by then; no weld seams. But that doesn't explain why later Tacoma models would have rust issues.

The only car I have had that had rust issues was the Mercury, which was over 16 years old when we got rid of it. An undercoating would have helped the bad body rust that was starting. It most likely wouldn't have saved the front strut spring, but definitely not the A/C compressor clutch, nor prevented the leak from the moon roof gutter to the cabin.

 

I live in New York (salt state). I just traded in my 2011 Prius and the under side was amazingly spotless. I would wash it 3-4 times at a drive in spray your self car wash ($3.00 for 8 min) during the winter. Spray wash it and use the wax setting and hit the under side from ever angle.