I have a 2013 Mazda 3 s GT 2.5L, it has 94K miles and the dealer has recommended a combustion chamber cleaning to remove carbon. I use a Top Tier gas in this car, is this cleaning really necessary?

 

If is a DI (direct Injected) engine so the gas NEVER gets on the back of the intake valve.
For normal injection there will still be some carbon build up depending on many factors.

The only real way to determine the extent of carbon is to scope the intake and the combustion chambers.

 

Is the 2013 Mazda 3s GT a Direct Gas Injection (DGI) fuel delivery system? I didn't think they were back then, but I may be mistaken. If it is NOT a DGI system, then I would not pay the dealer to do this......just for curiosity reasons......what is the price that they are quoting you to do this?

 

My 2013 2.5L is not a Skyactive, and as far as I can determine only the skyactive in 2013 is dgi and mine is not. The dealer quoted $200 for this service.

 

Mazda calls them DI and they first came out in 2011. Your Mazda may be depending on the month it was manufactured? Something you should find out.
If the cost was 200 that’s cheap if they do it for either type of injection system .

But as I said unless they scoped it they are assuming an unconfirmed condition based on your limited information about what they recommend it?