Vehicle & context:
Citroën C3 1.6 BlueHDi (DV6C engine, post-2015 AdBlue variant)
61k miles, full service history, runs clean, zero oil consumption between changes
I do all maintenance on schedule: oil & filter (Castrol Magnatec 0W30 C2 with PSA B71 2302 & 2312) + air filter every 6 months, fuel filter once a year
Timing belt, water pump, and tensioners done at 57k
No issues except the AdBlue system — a stupidly complex mess of sensors, heaters, level senders, and ECUs that eventually will fail.
What I had done:
AdBlue delete (software only)
EGR delete (software only)
Left DPF and regeneration system fully intact and functional
No increase in power or torque requested — this is a daily runabout, not a McLaren F1
The work was done by someone who’s been mapping ECUs for 15+ years — not some laptop cowboy. No hacks, no guesswork.
Emissions test – BEFORE & AFTER (same garage, same machine, 8 days apart):
NOx – identical
CO – unchanged
CO₂ – unchanged
Opacity – zero
Smoke test – passed clean
The technician said — and I quote — “You’ve not deleted anything, this is cleaner than half the new diesels we see.”
EGR delete – why it’s better for the engine:
EGR is a stupid band-aid on combustion inefficiency. It:
Feeds carbon-laden exhaust back into your intake
Gums up valves and ports (particularly bad on direct-injection engines like the DV6)
Creates soot load and turbo lag at low RPM
Causes twitchy throttle and irregular combustion at low load
Since the delete:
Throttle response is smoother and more predictable
No more low-speed hesitation or micro-judder in traffic
Engine sounds quieter, feels more refined
MPG up 2–3 depending on drive cycle
This is with DPF still in place and no tune changes.
MOT & legality:
UK MOT testers cannot plug into the ECU or scan for AdBlue or EGR status. The criteria are:
No warning lights
No excessive smoke
DPF visibly present (check with a mirror)
DPF regen still functions?
Yes.Unless you tell them, they’ll never know — and unless your engine’s running like a steam loco, they won’t care.
The Wynns AdBlue additive question:
Saw the post with the crystallised funnel and drain tray. That’s your answer.
Crystals = contamination. AdBlue is already corrosive, hygroscopic, and temperature sensitive. Introducing additives into a delicate SCR system is playing roulette with your injectors and tank sensors. Snake oil at best. Expensive system failure at worst.
Bottom line:
AdBlue and EGR systems exist purely to tick Euro 6/7 boxes in a lab — not because they make the real-world emissions better.
The fact that I deleted both and saw no change in actual measured NOx, CO, CO₂ or opacity confirms what many of us suspected:
Euro 6 is a compliance scam that makes engines worse, not cleaner.
Deleting AdBlue and EGR on a well-maintained car with a working DPF is the rational choice if you care about long-term reliability, cost, and actual emissions.
Happy to answer technical questions if anyone's interested.