Mazda switched unique 8 mm internal Allen drain bolt to standard 17 mm Hex drain bolt in 2018 MY when Mazda introduced cylinder deactivation with many changed on 2.5L. I believe the 2.5T received the same change in same 2018 MY on CX-9.
They both have good and bad for the application. IMO the reason why Mazda switched it is because internal Allen drain bolt is too easy to get rounded by those careless techs who seem to over-torque the drain bolt all the time.
You may have trouble to find 8 mm internal Alllen drain bolt right now as Mazda has switched to 17 mm flange Hex drain bolt for all engines. You’ll find the same part number, FS50-21-249, as the drain plug for ALL MY 2.5L and 2.5T’s. And it should be ended up with a Hex drain bolt, although the specific 17 mm flange Hex drain bolt used to use part number LFE5-10-404:
My mom has a 2017 cx5 2.5 AWD. Its always had dealer oil changes for its entire life. This time she wanted me to change it for her. I go under the car and remove the little access panel and the 8mm hex plug is stripped so bad I cant remove it. I know how to get it off but it would possibly damage it and its Sunday and I dont have another one ready to replace it. Anyone know what to say to make the dealership fix this? Do you think theyll try to fight it?
I've recently just stumbled across this thread but there appears to be alternative to LFE5-10-404. Based on what I am seeing, it looks like PE02-10-404 may be compatible as well, can anyone confirm? The tip of PE02-10-404 looks very similar to the OEM bolt that came with the CX-5. Assuming it's compatible, it would be $4-5 cheaper, not that it's a huge deal but just an observation.
I really liked the 8mm Allen and bought the correct size wrench for it. MAZDA changed back to the Hex because it seems that too many mechanics didn't have Allen wrenches and were trying to remove the drain plug with a screwdriver and a hammer. Can you believe that?