Subframe Rust - Need Advice

Hi All,

I have a 2012 Subaru Legacy 2.5i Premium with 41k miles that I purchased used in 2013. At the time of purchase, it had 19k miles, with a clean carfax. Anyway, today while topping off my windshield washer fluid, I noticed that was appears to be my front subframe has rust on it. I live in a snow belt state, and wash my car weekly (with an undercarriage rinse). Additionally, I power wash it every spring to clean the residual salt out if any got in.

I have noticed that with the Subaru (and others have confirmed this as well), but for some reason, the Subaru’s engine bay (below the CVT housing) usually collects snow if driven through deep snow. Unfortunately, it takes awhile for it to thaw out, even after being parked in a garage. I am not sure if this is what is causing the rust. I have noticed the rust on both sides of what I believe is the subframe of the engine.

I have never owned a Subaru, so I am not sure if this is something that is normal and OK (safe) or if I need to call Subaru and complain. I do have the extended bumper to bumper warranty, but if the rust hasn’t perforated anything, I’m not sure that Subaru will do anything?

I really would appreciate some advice. Also, here is a link to a picture of the rust. I tried my best to get the area, but it was kind of hard with everything else in the way.

Normal for salty area.

That´s normal in areas where salt is used to smelt snow and in the coast. And if Subaru says it hasn’t penetrated anything then there you go! No worries, but if you are freaky with your car and want to be extra careful with your machine then: 1) check under the whole car for any other rust points, remove the rust, and paint it, preferably use something like this: 2) power wash under your car after snow season/storms.

Oh and check your wishbones! I know the second part to get rusty after the Sub frame is the wishbone, and in Subarus is common and that´s a structural risk!

If you really want a super tough coating, try using POR15. A little pricey and will have to wear off anything it touches like your hands if you don’t wear gloves, but one of the best coatings around. One of the members here likes to use oil once a year to prevent rust.

Thanks guys for your help! Also, what is the “wishbone”? I am not super car savy. If it was really bad, wouldn’t Subaru mention it to me during their inspection when I take the car in for an oil change?

Also, my car has a CVT transmission. What mileage would you guys recommend replacing the oil in there, and how reliable do you all think the CVT’s are? I’ve read mixed reviews on it.

Where was the car originally registered by the first owner? It’s on the CarFax.

Illinois. So, it has seen snow/salt.

This is a sturdy part and rust on the surface is usual. One sure preventer is to take a tube of wheel bearing grease and paint it on with a foam brush. Check any underneath components like these and treat them similarly each year. They will last forever and it looks good with the sheen on it. Bearing grease is cheap, works and doesn’t bother your skin. They make it in biodegradable form also from G-oil. Over the years as the coating builds up and a little dirt gets on it, it will out live the rest of the car.

I know this is going to raise the ire of some folks, but I strongly recommend that you discontinue the weekly undercarriage rinse. These processes have been shown to promote rust by driving water into cavities that can’t ventilate and dry, cavities that aren’t normally filled with water.

The rust in these photos doesn’t look serious to me. You could if you’d like treat it with one of the treatments recommended by other posters.

In salt areas, rust underneath the car is seldom the worry. It’s the body cavities including doors, rocker panels, fender liners eye. . This is a unibody car, very easy to coat and they seldom if ever start rusting underneath from the out side. If you are taking all that time to spray water under your car, take 10 minute in the fall, fill a Garden sprayer with 2 quarts of biodegradable motor oil from g-oil, and spray the under neat and back up every door or rocker panel drain hole you can find.

Personally, I would just crawl under once in the fall and paint all areas with grease that you worry about. Be that as it may, that is not your main rust areas of concern. A untreated Subaru first will rust like heck around the rear quarter panels no matter how muc you spray underneath.

I would not know if there is something to not spraying cars underneath because I never wash my cars during the winter but wait till spring. My cars NEVER rust in the ten to twelve years I own them. Anywher water could be driven up into body panels, I have coated with bio motor oil from the fall before.

I really don’t know how under washing without follow up coating can help. The body panels are already coated with a factory coating. Rust through the floors comes from above where peopl track the salt in on their shoes…how is spraying going to help there.

Like I said…Subarus rust in areas like all other cars do first and spraying underneath is NOT the first line of defense. It’s the other stuff you do in the fall that no one seems to car about…then continue to fool themselves that washing alone will make a car last…a fools errand.

Tough call, I think it may be more model dependant in the rust belt. Now my 72 f150 ford pickup truck would waffle in 2 different directions in a turn, and the 71 nova welded a plate to hold the shck in place, traded them in in 90, my bad, and an intern with a 14 year old car not wanting to drive on bumpy roads as told is frame is rusted out and no hope.

If you can paint a fence, you can paint a frame…with grease. Do it every few years and it will never rust.

If you are worried about rusty subframe, control arm or brake and fuel lines go to an auto body supply house and get a gallon of rustproofing that can be either brushed or sprayed on. A coat of oil in the fall will be gone by Thanksgiving around here.

Check the red part for rust.

Also, my car has a CVT transmission. What mileage would you guys recommend replacing the oil in there, and how reliable do you all think the CVT's are?

I change my Insight CVT oil at least every 30K (per mfr); it’s easier than changing the motor oil. CVT reliability does seem to be hit or miss. My guess is that the “misses” are lead-foots.

Just make sure you use the EXACT CVT fluid from Subaru, no substitutes allowed!

Subaru currently does not recommend changing the CVT fluid at all, except under severe driving conditions, (which includes any winter driving), in which case, change it every 25k. But I’d change it at 30k intervals even under non-severe conditions.

edit: similar rules apply to the differential fluids, but the interval is 15k

I will have the wishbone checked for rust. Also, I talked to Subaru, and they told me no maintenance was required on my CVT Transmission. I find it hard to believe that any tranny fluid lasts forever, but I wasn’t sure. I currently have 41k miles on my car, so it’s probably time to change it!

Yeah I change my 100,000 mile fluid too at 30,000. Like the trans shop said “no such thing as lifetime fluid”. Given the CVT problems, I sure wouldn’t skimp on the service and gee half the country and I suspect more than half of the population would be in winter conditions.