I use this diesel fuel system cleaner to my Mercedes GLC250d every 10,000kms.
Unlike petrol, diesel sold in Australia does not contain much cleaning agents (e.g. injector cleaner). Using this diesel fuel system cleaner at every service interval is a good idea.
Also, a lot of Nulon additives are on 40% off sale now.
Nulon Pro-Strength Diesel Turbo Cleaner 500ml $14.99
Nulon Pro Strength Extreme Oil Flush 500mL $13.79
I'll wait until the blinker fluid is on sale