I find that interesting in 2016 when i bought my P1K5 the dealer beat me over the head to only use Honda oil if i have a warranty claim (bought the 5 year) and oil was found to be the issue and it wasn't honda's oil it voided my warranty. They said that over and over to make sure I only use honda oil.
As a tech have you seen an engine fail due to oil and Honda snub their nose it wasn't our oil used and screw the customer?
Void what warranty? Every part of the vehicle's warranty? That would be completely illegal according to the Magnuson-Moss Warranty Act.
Even their manuals say what type of oil to use but do not require or demand that it be Honda oil, they cannot do that because of the Magnuson-Moss Warranty Act.
There is no way (legally) Honda can deny you a warranty claim or void any part of your warranty for using other oil unless that oil doesn't meet the specs as required in your owner's manual. If they denied a claim, that would violate federal law.
If you had an engine failure and were using any premium oil as good or better than recommended, they would have to honor their warranty.
The ONLY claim they could deny is for any wet clutch issues if you used an oil with friction modifiers, energy conserving, etc. because the manual specifically states it "may" harm the clutch.
So, I believe a dealer telling buyers that the use of other than Honda oils MAY result in a claim denial concerning the wet clutch warranty is appropriate but telling them it "Voids the Warranty" is downright a lie and possibly a criminal act. Honda cannot "Void your Warranty" for using non-Honda parts and they cannot demand that you use only Honda parts, they can only deny a claim and you can fight a denial but they cannot ever void your entire warranty for any reason.
You need to find yourself a new dealer. I had a knuckle break and I flipped my Talon (or it could have been the other way around, no one really knows). Honda could have easily said it was my fault and told me to take a hike but instead, my (very good) dealer stepped up, worked their asses off and between Honda America and the dealer, they made it right and reimbursed me for the broken parts i replaced months prior AND the damage the flip caused. They made me completely whole again. If you are getting less than that for service from your dealer and/or getting lied to so they can sell you some oil and parts, you might want to look for a new dealer.
Here is a summary of the law...
In a Consumer Alert issued by the Federal Trade Commission (FTC), the agency confirmed that
“The Magnuson-Moss Warranty Act makes it illegal for companies to void your warranty or deny coverage under the warranty simply because you used an aftermarket part.” The alert outlines key provisions in the law that provides protections to car owners. As defined by the FTC, an “aftermarket' part is a part made by a company other than the vehicle manufacturer or the original equipment manufacturer.”
“The FTC’s reference to aftermarket parts is equally applicable to specialty parts,” said Russ Deane, SEMA’s General Counsel.
“Under the Magnuson-Moss Warranty Act, the warranty cannot be conditioned to a specific brand of parts, services or vehicle modifications unless those parts or services are provided free of charge.”
The alert notes that a consumer has the right to patronize independent retail stores and repair shops for parts and service without fear of voiding the new car warranty. The dealer/vehicle manufacturer has the right to deny a warranty repair but they must demonstrate that the aftermarket part caused the problem. The warranty remains in effect for all other covered parts.
The FTC alert may be downloaded using this link.
The alert was issued in response to an FTC complaint filed last August by the Automotive Aftermarket Industry Association (AAIA), Automotive Oil Change Association (AOCA) and the Tire Industry Association (TIA).