Questions about de-carboning my 15 Mazda 6

I went to my local Mazda dealer to get my regular scheduled oil change and they recommended that I get a service to "de-carbon" the engine because my 2015 Mazda 6 was bought new but has now reached 30,000 miles. It has never had any de-carbon services done yet.

In my experience, many service centers try to up-sell services, some of which is not really necessary. I thought that is what was being done here so I declined the service and just proceeded with the oil change.

I went home and researched engine decarbonization for a 2015 Mazda 6 and too my surprise I found out that this actually is something that should be done on what is called a GDI engine. I actually learned what a "Gasoline Direct injection" (GDI) engine is and that the 2015 Mazda 6 has a GDI.

Apparently, with a regular engine, fuel washes/runs over the top the intake valves and then runs into the cylinder to get burned. In a GDI engine, the fuel is directly injected into the cylinder to get burned and no fuel runs over the top of the intake valves.

In a regular engine, a good quality "top tier" fuel has cleaning agents that can keep the tops of the intake valves clean of debris (unburnt oil, fuel etc.) by washing it away as the fuel runs over them. This debris if left is burned with high heat and this turns into carbon if not washed away. The carbon slowly builds and accumulates with time. Because no fuel runs over the tops of the intake valve in a GDI engine, the debris gets burned and turned to carbon much faster unless extra measures are taken. That extra measure is either running a chemical over the intake valves periodically for prevention or, actually removing the valves to manually clean them (if left unmaintained).

As usual, prevention seems like a much cheaper and better alternative. An ounce of prevention beats a pound of cure.

I have a few questions for the community:

1. What is a good product/chemical to run over the intake valves to keep them clean?
I am leaning towards this product: CRC GDI Intake Valve cleaner

2. It looks like the above intake valve cleaner is run through the air intake system but should I inject this directly into the throttle body or should I keep the main tube attached to the throttle body to maintain a vacuum?

3. If I keep the air tube attached for a vacuum, what tube/hole/area should I remove to inject this product into?
Pictures would help as there seem to be a couple of rubber hoses I could remove.

4. It looks like this product requires the engine to be revved while being injected into the air intake system but I will be performing this procedure myself so how can I rev the engine from the engine bay as I can not be two places at once (though sometimes I try)?

On my other older vehicle, the vehicle had a metal lever attached to a spring that had a cable that ran to the pedal in the cabin and by moving this lever I could rev the engine.
I looked and do not see this lever in the 2015 Mazda 6.
5. Where is this metal throttle lever located?

6. How often should I perform this service?
I wouldn’t mind doing it every 5,000 to 10,000 miles if it prevents costly repairs

7. Are there any other “decarbon services” I should perform on the vehicle every so often?

Thank you.

 

I'm curious, how much did the dealer want to charge for the service?

 

$125

I re-called the dealership where I get my oil changes done just a few minutes ago to re-check and all that they are doing is just running the "engine top cleaner" through the intake system (to clean the intake valves on the GDI engine) and putting a "cleaning product" in the fuel to "continue to clean".

Basically they are charging a really high price to run a Lucas oil (or similar injector cleaning product) in the fuel and to run a $10 - $20 "engine top cleaner" product such as Seafoam or CRC through the intake system (as close to the throttle plate as possible).

I'm still interested in some Mazda vets answering my questions asked in the original post.

Thanks.