What is the long-term impact of the EGR system on LMM engine longevity?

[LowGearLegend]

I just pulled my intake bridge on my 2009 Duramax with 120k miles and I couldn't believe how much soot was caked inside. It looks like a clogged artery. If the EGR is shoving all that carbon back into the cylinders, WHAT is it doing to the cylinder walls and the engine oil? I’m trying to decide if a reroute/delete is a "want" or a "need" for someone who plans to keep this truck past 300k miles.

 

[CodeCavalry]

That "clogged artery" you're looking at is exactly why many LMM engines struggle to make it to high mileage without issues. The soot isn't just sitting in the intake; it acts like an abrasive paste when it mixes with the oil film on your cylinder walls. Over time, this leads to increased ring wear and cylinder scoring. If you want to see 300k miles, getting that soot out of the intake is a "need," not a "want." Even if you can't do a full delete, at least look into an EGR reroute or a high-quality catch can to stop the oil vapors from mixing with the soot and creating that sludge.

 

[GothamRanger]

That "clogged artery" is exactly what’s circulating through your combustion chambers. The soot being shoved back in is essentially carbon, which is an abrasive. When it mixes with the oil film on your cylinder walls, it acts like a fine-grit sandpaper, accelerating wear on the rings and cross-hatching. For a truck you want to keep for 300k miles, stopping that soot intake is a "need." If the cylinders lose their seal early due to that abrasive wear, you'll start seeing massive blow-by and oil consumption long before you hit your mileage goal.