2018 cx-5 Blown Head Cylinder and Head Gasket
This is more about the WARRANTY. Honestly I have you beat. I own a BMW with 36k miles and it is 2002. Bought it new. So maybe if my engine blows I should go to BMW for a new engine? 
I already read your response on the other thread. You can go see my response.
Mazda CX-5 2018 Head Gasket Failure - Page 3 - Mazda Forum - Mazda Enthusiast Forums

I already read your response on the other thread. You can go see my response.
Mazda CX-5 2018 Head Gasket Failure - Page 3 - Mazda Forum - Mazda Enthusiast Forums
warranty is 3 yr/ 36,000. We purchased as new 2018.so 6 yrs/25,000 miles.
We have similar tastes in cars I see. I have a 2006 BMW M Roadster with 20k miles.... Point taken on the complaint when the car is out of warranty. In this case, it may be worth asking Mazda corporate, as they are only 1 yr past the 5/60 coverage. You never know if you don't ask.
I try to post this before feeling negative about any dealership. You can also ask that the dealership ask Mazda Corp on your behalf as well. If I had to place the best would be if dined at the dealership level, have them contact the Auto manufacture t, if that fails then personally contact the auto manufacture. I would also create a "paper Trail" of all the attempts, just in case.
Without guessing you really need to read your WARRANTY that you were given. But I understand they can be confusing at times so rather then get a forum answer (we dont at least at this poing know your complet on record service history) I suggest to talk directly to a Mazda Service advisor in person and if you do not understand the exact WARRANTY for your Mazda have them explain it to you.
Here's the warranty booklet for the 2018 model: https://www.mazdausa.com/syssiteasse...ty-booklet.pdf
I can personally state having been on the side of the owners in a suit that they loose if they don't have a detailed record of required service during the warranty periods. I was involved to give an example with replacing a transmission in a car that was denied warranty yet was still under the manufacture power train warranty only because they did not do the required brake serving and engine oil and filter required services. I tried to give my testimony that brakes had nothing to do with the transmission failing but the attorney's for the auto manufacture simply stated that because the service schedule was not done that they were with in their rights to disallow any warranty claim. My customer lost the suit . I have several example or similar cases but I think you all get the point.
It so easy...
If you have a concern no matter what it is...and you are still under a new car warranty go to the dealer and get the concern added to your VIN. This way if something happens you at least have proof you came to the dealership.
Don't skip or delay any service that is required on your vehcle service scheduling. Skipping even one or delaying one for several hundred miles or less could come back to bite you with a warranty claim rejected.
If you get any SAFTY recall or notification to have something checked or replaced, make contact ASAP with your local dealership. Make an appointment. Even if you must reschedule at least it looks like you are trying to take care of it. Make sure you always reschedule. If it is a SAFTY recall don't let it go more then 90 days.
If you ever get denied a WARRANTY , don't come to forum and beetch about it, contact an attorney (at least a free clinic) and seek advice. No one on a forum is going to really know all the details about your specific denial unless you submit every document concerning it and then only a very small number of members can actually help anyway. Unless they are a contractual attorney at Law?
Last before you get out of auto manufactures service performed on a warranty you were denied make sure that you get the service shop to document on your work order why you went to then for the service in detail. Also ask that they give you a mor complete detail explanation of the service and any and all parts they replaced. And ALWAYS KEEP ALL THE REPLACED PARTS even if it is a engine or tranasmission.
ASE
If its an oil leak from the engine then yes, it would likely be a powertrain (engine and transmission) issue, but as Callisto said, start with the dealer and move to Mazda corporate if this fails. You may not win, but we are likely talking about a hefty bill, so why not try?


