26,000 miles over three years equates to around 8,000 miles each year, which is the UK average.
You can drive once a week to get that miles, or you may drive every day. Even if you drive every day, it is still 20 miles per day, which is enough to warm the vehicle even in stop-and-go traffic. When the engine is cold, the stop start mechanism does not function.
The carbon buildup issue is more of a design characteristic of these engines. They were not built to be driven in stop-and-go traffic, yet that is how the roads are today.
Nowadays, the phrase "driving on the highway" might be deceptive. The freeways in the UK have the highest speed limits, yet try travelling to work and you'll discover that you spend a lot of time stopped with the handbrake on.
Then you try again on weekends, and it's somewhat better. The majority of individuals drive their automobiles to work and away on vacation. In both cases, they utilize the highways merely to be parked and idling to remain warm or cool.
Highway driving used to imply faster speeds, which required more rotations. This had the capacity to remove accumulated dirt. However, since modern highway traffic is sluggish, the statement should be replaced with something like "drive the car long enough without stopping."
The speed and rotations are unimportant as long as you can keep the automobile going in top gear. Then you have the opportunity to burn off the accumulated dirt.
However, the natural combustion cycle of these engines produces an excessive amount of carbon. You cannot prevent dirt accumulation if you simply use your automobile for commuting, shopping, and vacations.
Fortunately, most drivers do not face this issue since they finance their vehicles and exchange them every couple of years. For the unfortunate drivers who do not do so, the decoke is an excellent way to compensate for the poor design.
The second solution is to get some fresh air by driving away on weekends, although most people do not do this. If people gave the automobile some respectful time to go without stopping, it may clean up a little, but the issue would return with the current traffic situation.
When the latest version of E Class was debuted, the engine was said to run at 1,100 rpm at 70 mph owing to its 9-speed gearbox. So, contrary to popular belief, driving on the highway will clean up the engine. This will occur not because of the low revolutions, but because the engine will run continuously.
Mazda never got the diesel engines right, but they're not going to acknowledge it.