You're in Canada right? All new Mazdas have a 7-year perforation warranty. Some salespeople mistakenly say that it covers rust, but it really just covers structural rust damage, not surface rust.
In the US the corrosion warranty for a 2020 CX-5 is for 5 years. My US 2016 Sienna is warratied for 5 years for "corrosion perforation of sheet metal only" which is typical in my experience across various makes and models. I don't recall ever having a US rust-through warranty that covered "structural", such as the chassis. I'm not sure my 2020 US CX-5 covers anything other than body panel rust-through. I'd be surprised if it did.
With all this recent (and not so recent) discussion of Mazda rust problems I was wondering what I might have missed in researching my recent 2020 CX-5 puchase.
Consumer Reports' reliability ratings from this past April for CX-5s dating back to 2013 show a record that is about as good as it gets across makes and models, especially in this price range. Some Lexus models fare better, others worse. From 2017 on, the only CX-5 ratings that are not above average is an average rating for in-car electronics in 2017. The only below average ratings in prior years are for brakes in the 2013s, in-car electronics in the 2014s and 2016s , and power equipment in the 2016s. Other Mazda models have not fared as well.
Are these CX-5 owners missing the boat, not reporting their problems, rust or otherwise? As a spot check, there is this Mazda recall for rusty brakes in a couple of other Mazda models and years:
Two popular Mazda cars are being recalled for a rust-related problem, but it may not be visible to all owners. The 2014 to 2016 Mazda3
www.carsdirect.com
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The Mazda3s in that recall scored below average per Consumer Reports for brakes in 2014 and 2015, average for 2016. The Mazda 6s for their recall years scored the worst ratings for brake reliability. Even if an owner incurs no cost or performance issue, Consumer Reports advises them to downgrade ratings for time sucks at the dealer. These ratings are in keeping with the extent of the recalls.
This leads me to a couple of observations:
1) A problem wth one model year may not apply to another model or year from the same maker. That's pretty obvious. You cannot project problems from one of a maker's models to another in the same year. That's pretty obvious as well.
2) I may have been premature in blanket advice against any aftermarket rustproofing. Under the most extreme conditions, say 7 months of Canadian salty commutes with a car parked outdoors that is not fastidiously sent through regular undercarriage washes, it may not be a bad idea to have it subjected to an aftermaket rust proofing treatment. Conversely, I've subjected several Toyotas, a Honda and even a Chrysler to long slushy commutes in the Chicago region over many miles and years without any such issues. However, those vehicles were garage kept and frequently run through a car wash with an underbody spray. At the very least, the value of these rustproofing treatments should be regarded as situational with the devil in the details.
3) Regardless, I would strongly advise against any aftermarket rust prevention treatment that involves drilling into the vehicle. Further, Ziebart talks about their oily treatment as being superior to tarry treatments that can actually trap moisture and cause corrosion. They don't seem to be averse to drilling into vehicles, however. Whatever methodology one is considering, I'd get a copy of the manufacturer rust-through warranty to see if such treatments would void it. Since I don't intend to do this I'll leave that to others to investigate.
4) Surface rust may or not be a sign of worse problems to come. Buildings and bridges have been built with skins designed to accumulate surface oxidation as a protectorant, the USX headquarters in Pittsburgh an early demonstration project. Whether surface rust on a particular Mazda part is expected, that would be a question for a Mazda engineer. My 2006 Accord's brake calipers left rusty drips on a spanking new garage floor 7 years ago without any problem since. I think it is fair to say Honda engineers expected that.
5) The shortcoming of a Consumer Reports reliability rating is it lumps all vehicles and all trim lines from a model year into one bucket. There are several problems with this, but in general it is worth considering that each vehicle is unique. With some 30,000 - 40,000 discrete parts, a person or robot can reach into bin and grab a perfectly fine part on one vehicle and then a defective part from a different production run on the next vehicle. A production machine or robot or person could be miscalibrated at one moment, the problem discovered and fixed the next, with the first one sent through as "within tolerance". Or it could be weeks or months with the problem going undiscovered and if there isn't a safety problem requiring a recall it gets a service bulletin...or not. A problem could be a one-off. I recently had a set of new Toyota OEM brake pads start squeeking right of of the dealer shop. After two trips back to the dealer they couldn't identify the problem other than possibly impurities in the pads. They replaced them under their own service warranty with no problem since, the same part off the same shelf two weeks later.
6) In the end, with perhaps 100,000s, if not millions, of a particular make and model sold worldwide out of mutiple factories with parts from mutilple suppliers, there really isn't a "model year" or half model year--there's only you, your car and your situation. So you have to guard against too much anecdotal complaints from others with their cars and their situations. If you see 4 complaints about a particular thing in these pages you have to ask about all the thousands or hundreds of thousands of folks not complaining.
7) For that reason, no matter what the reliability ratings say from whatever souce you choose, you're playing the odds with those ratings and that is the best you're going to do. I'm liking my odds with the Consumer Reports' ratings and will not be buying any extended warranties or rust proofing or any paint treatments for this Soul Red, despite reports of issues with that color because it looked just fine at the 4,000+ miles it had already. So, make your bets and take your chances.