EGR. Necessary evil?

[Brian Howard]

Hello everybody.
I have a 2011 A6 Allroad Avant 3.0L diesel with 173000 miles on it. I bought it a year ago privately and I am very happy with it. This is my 8th Audi, my 2nd Allroad Avant.
Ever since I have had it, the EGR has been playing up with the MIL coming on. I get it switched off when serviced, but it comes back on after just a few journeys. I have had it diagnosed and it's showing a grade 3 fault with the EGR cooler/valve. (I was a VW/Audi mechanic some 50yrs ago, but these modern engines are beyond me!). I have used a few diesel cleaner additives, (Wynns, STP) which appeared to have worked, switching the light off, but only for a while. (My shortest journeys are usually 20 miles or more, I don't do short trips to the shops etc)
From invoices provided by the previous owner I can see....
The EGR cooler assembly was replaced in Sep 2022 (Parts cost £655.94) at 139691 miles. (This is the wording from the invoice)
A year later, Oct 2023 the EGR valve and cooler was replaced (Parts cost £707 inc VAT) at 153795 miles.
I don't like having the light on as I am concerned that if another fault is detected with something else, having the light on already will not allow me to see this, and it could be a more serious fault.
Another Audi owner (A4 3.0L 2010 similar engine) says that I could have the EGR system blanked off, so that it is no longer operating, and so would not keep switching the MIL on.
He has had it done to his by a garage and it runs fine. The EGR and valve is still in situ, but it's no longer operating. He said that as there was less carbonised air feeding back into the combustion chamber, less was getting back into the sump, via the rings and so his oil was less contaminated. He showed me his dipstick (!) and I have to say it was the cleanest oil I have ever seen. It was amazing.
It's my understanding that one of the main functions of the EGR is to reroute warm post combustion air back into the inlet manifold to get the engine up to operating temp more quickly. That seems like a good idea!
My questions are...
Is this a viable solution to the problem of the MIL lighting up?
Are there any consequences to having this work done?
Any help or information is greatly appreciated.
Thank you

[Crasher]

The main purpose of EGR is to REDUCE combustion temperatures by mixture dilution which reduces the various oxides of Nitrogen production, commonly known as NOX, such as Nitrogen Dioxide… i.e. gases that kill living things. A quick search gives the following

Nitrogen oxides (NOx) harm life by causing respiratory and heart problems in humans, leading to lung irritation, asthma attacks, and increased mortality, especially in vulnerable populations. Environmentally, NOx contributes to the formation of photochemical smog and acid rain, damaging vegetation, reducing crop yields, altering soil chemistry, and affecting biodiversity in sensitive ecosystems. Some NOx, like nitrous oxide (N₂O), also act as a greenhouse gas and can induce short-term euphoria, but inhaling it in high concentrations is dangerous.

Effects on Human Health

• Respiratory Issues:
  Inhaling NOx can irritate and inflame the respiratory tract, leading to coughing, shortness of breath, and an increased susceptibility to respiratory infections like pneumonia and bronchitis.
• Aggravation of Existing Conditions:
  People with asthma or heart disease are particularly vulnerable to the adverse effects of NOx, which can trigger or worsen asthma attacks and increase mortality from cardiovascular and respiratory diseases.
• Severe Symptoms:
  High-level exposure can cause serious symptoms such as pulmonary edema (fluid in the lungs), chemical burns on skin and eyes, and, in extreme cases, a life-threatening situation due to inadequate oxygenation of body tissues.
• Mortality Risk:
  Long-term exposure to NOx is associated with an increased risk of all-cause mortality, as well as deaths from cardiovascular, respiratory, and non-accidental causes.

Environmental Effects

• Photochemical Smog:
  NOx reacts with sunlight and hydrocarbons to form smog, which reduces visibility and has the same irritating health effects as NOx.
• Acid Rain:
  NOx contributes to the formation of acid rain, which can damage vegetation, reduce crop yields, and alter the chemistry of soil and water bodies.
• Ecosystem Damage:
  Deposition of nitrogen from NOx can change soil chemistry, leading to shifts in plant communities and negatively impacting biodiversity in sensitive habitats.

Other Effects

• Nitrous Oxide: While other NOx are harmful pollutants, nitrous oxide (N₂O) is also a powerful greenhouse gas. Although used for medical purposes to induce a calm state, inhaling N₂O in high concentrations can cause serious health problems, including impaired cognitive function, nerve damage, and blood clots.

[Roverfan]

It'd be interesting to see what code or codes you are getting for the egr. Some restricted flow codes are due to carbon buildup inside the pipes

I only use recommended oil spec (VW 504/507 on mine) partly in the belief the acea rating (c2/c3) helps keep the egr from clogging.Another old wives tale theory I have is limiting excessive idle time. As turbos are accepted to let a bit of oil go into the exhaust at idle, limiting idle time makes sense.

Also no snake oils/additives as many are made for use in older petrols and can be harmful to DPF becoming extremely corrosive to some substances at high temperatures. The alloy egr on my model is extremely sensitive to water.