Hi all, I'm new to the world of Mazda and new to the forum. I just purchased an '18 GTR in Soul Red Crystal and brought it home from an out of state dealer.

Having read probably hundreds of posts about oil recommendations in various car forums over the years, I kinda hate for this to be my first post, knowing the responses will likely careen from "policy/warranty compliance" focused to "application / YMMV" focused to "old timey DIY wisdom" based. (Oh, almost forgot: Many responses will be "Amsoil fanatic" based.) But here goes anyway!

Page 6/22 of the manual says

SKYACTIV-G 2.5T: Use SAE 5-30 engine oil....Mazda Genuine 5w-30 Oil is required to achieve optimum fuel efficiency. For maintenance service, Mazda recommends Mazda Genuine Parts and Castrol (brands). Only use CAE 5w-30 oil "Certified for Gasoline Engines" by API.

All of the service records for the car, which was serviced religiously at the originating Mazda dealership, indicate that the dealer ONLY used 0w-20 full synthetic oil for each and every oil change it performed.

I am inclined to follow the manual, so that if I am ever questioned as to my maintenance practices during, let's say, a discussion about future engine work under a powertrain warranty claim, I can indicate I followed factory guidance.

What are you inclined to do? Thanks for any input! (I feel like I just pulled the pin on a grenade...)

 

An update: Yesterday I got the car up on ramps and changed the oil to Castrol Edge 5w30. I did not replace the filter as it's still new. I did install a Fumoto F106N oil drain valve ($23 on Amazon) and picked up 10 feet of drain hose at Home Depot for $3+, so next time the change will go fast and easy. I noted that the access panel was missing one of its two screws (again, thanks Mr. Dealer! who just changed the oil 2 weeks ago) so I will get a replacement. Meanwhile, regarding the other two fastening points: Those plastic push fasteners are not easy to re-insert, are they? In the many cars I've maintained, I've never seen these used on a frequently removed panel. (On other hand, it was 22 deg. here in Chicago area yesterday, so my fingers were a bit numb.) Kudos to Mazda for a very easily accessible drain plug and filter.

 

I’m really surprised your manual says 5w-30. My 16 specifies 0w-20 is USA, but 5w-30 if you live anywhere else. I used 0w until the warranty expired but now I’m switching to 5w-30.

 

Good choice of oil viscosity Elkins!
The oil to use in a MAZDA is "RECOMENDED:" not required. Using either or I sincerely doubt would void the engine warranty even if you used some other viscosity choices. Having used and had oil analysis done during the first 30kmiles on my 2018 2.5 I saw no advantage in any respect MGG, power or wear using other viscosity outside the MAZDA "recommendation" but still within the operating specification which were mainly the ambient temperature's. I am getting ready to do my 3000-mile oil filter and oil change using a MAZDA oil filter and RED LINE 5w30.

 

As a reminder, we are talking the 2.5T oil spec. From what I have read here-and-there, the spec moves from 20w to 30w in order to keep the turbocharger happy.