TL;DR:
- Seven full seasons applying Rust Check at this shop. Not one customer has ever come back and told us their warranty was voided over it.
- Ask the dealer the question back: will your warranty cover rust damage in the first place? Salt-belt perforation rust is usually the exact thing it excludes.
- The drilled access holes are small, they go into cavities designed to be plugged afterward, and we have never seen them be the reason a claim was denied.
- Hybrid owners hear this warning the most. We spray oil only where water and salt already reach anyway, so it protects the exposed electrical areas rather than putting them at risk.
If you search whether rust proofing will void your new-vehicle warranty, you will find a lot of pages telling you to be careful, and a lot of dealership sales staff who will tell you flat out that it does. It is one of the most common worries customers bring into our Bowmanville shop, especially people who just drove a new vehicle off the lot.
Here is the short version before we get into it. We have been a licensed Rust Check dealer since 2009, and personally we are going into our eighth Rust Check season. In seven full seasons of applying this product, we have never once had a customer come back and tell us their warranty was voided over it. Not once. We have heard the warning line for years. We have never seen the other side of it actually happen.
The question we ask back
When someone tells us they are worried the dealer said Rust Check will void their warranty, we usually ask them one question in return.
Will your dealer warranty rust damage in the first place?
Customers usually stop for a second when we ask that. It is a good point and they know it. The dealer is warning you off protecting your vehicle from the one thing the warranty almost certainly does not cover. Perforation rust from Ontario road salt is exactly the kind of long-term corrosion that factory warranties exclude or heavily limit. So the warning is steering you away from the protection and toward the exposure.
We are not saying that to be clever. We just want people to notice which side of the deal each party is actually on.
Will Rust Check void your factory warranty?
In our direct experience, no. Seven seasons in, we have not seen it happen.
What we can tell you is what comes back through the door. Vehicles we have been oiling for years still go in for warranty work, and the oil has never been the thing that came up. If manufacturers were voiding coverage over a proper oil application, seven seasons of customers is long enough that we would have heard about it by now. We have not heard about it once.
If you want to be completely sure for your exact make and model, the honest move is to read your own warranty booklet or ask the manufacturer directly, not the salesperson trying to sell you the dealership's own coating package. The person telling you Rust Check voids your warranty is often the same person selling you a rubberized undercoating add-on. We wrote about why we stopped applying that dealer undercoating entirely if you want that side of the story.
Do the drilled access holes void anything?
This is the specific version of the fear, and it is the line dealers reach for most. Drilling the small access holes for rust proofing will void your warranty.
The access holes are small, they go into cavities designed to be sealed with plugs afterward, and they are how any proper oil application reaches inside the doors, rockers, and frame rails where rust actually starts. In seven seasons we have never seen those holes become the reason a warranty claim was denied. If you want to see exactly what that step looks like before you book, we walk through the whole process in our what to expect at a Rust Check appointment post.
The reason the drilled-holes line sticks is that it sounds technical and permanent. In practice it is the same scare-tactic framing as the warranty warning, aimed at keeping the rust-proofing dollar at the dealership.
Why are hybrid owners told this the most?
If there is one group that walks in carrying the most warranty fear, it is hybrid owners. For whatever reason, the worry that undercoating will damage the electronics or void coverage is baked deeper into hybrid buyers than anyone else. A Prius owner or a RAV4 Hybrid owner will bring it up before we even get to the vehicle.
Here is the honest breakdown. If we were talking about the thick rubberized stuff, some of that concern could have merit, because that product behaves very differently. But that is not what we apply. We spray oil, and we only spray it where water, salt, and dirt can already reach naturally. If a spot is exposed enough underneath your vehicle for moisture to get to it, that is exactly where the oil belongs. We are not introducing exposure to anything that was sealed.
What the oil actually does is displace moisture and protect the metal and the electrical components sitting in those exposed areas. So for a hybrid, a proper oil application is working in favour of the electronics, not against them. We go deeper on this in our Rust Check for hybrid and electric vehicles post, because it is the single most common warranty conversation we have.
What the dealer line is really about
Strip it all down and the warranty warning is a sales tool. It is not that the people repeating it are all being dishonest. Many of them simply repeat what they were told to say and have never seen a rust-proofed vehicle come back three winters later. But the effect is the same. The line keeps you from protecting your vehicle against Ontario winters, and it often nudges you toward the dealership's own coating instead.
We have written before about the rust-proofing myths that keep circulating, and the warranty one is near the top of the list because it is so effective at creating hesitation right when a new-vehicle owner should be starting protection.
The Bottom Line
Seven full seasons in at our Bowmanville shop, not one customer has ever come back to us with a voided warranty from Rust Check. We have heard the warning line hundreds of times and never once seen the outcome it threatens.
If you have a new vehicle and the dealer is telling you rust proofing will void your coverage, the practical move is simple. Read your own warranty booklet, remember that it almost certainly does not cover salt-belt rust anyway, and get the protection that actually addresses the Ontario winter your vehicle is going to spend the next decade in. Our Ultimate Rust Check is a two-step oil application, and the annual cadence is what actually keeps a vehicle solid underneath.
Give us a call at 905-439-2338 or book online. We're at 161 Baseline Rd E in Bowmanville, serving Oshawa, Whitby, Ajax, Courtice, Newcastle, and all of Durham Region.