EGR myths and cold starts.

[skyship007]

Many Volvo diesels are fitted with EGR valves designed to cut Nox emissions that are real health risk factors. The engines ECU warm up program is designed with the EGR functioning, if it fails or some twit deletes it (New MOT failure point), the engine takes longer to warm up and it is the period the mixture is richer than normal that causes the most in cylinder deposits. If the engine was designed with an EGR present they do not increase wear rates but reduce them!

The difference in fuel consumption is minimal unless it blocks, as it will often result in a faster warm up time, even if there is a loss of a few percent when warm. Tiny Carbon particles recirculated by an EGR are very soft in comparison with cylinder head components, and they make no difference to ring or valve guides (Tiny sand particles are a very different story). If the cylinder walls or valve seats are pitted from corrosion (Use of high Sulphur fuel or simple lack of use), they even help by filling in the tiny crevices.

For a diesel in good condition, the EGR often only needs cleaning every cam belt service (Mine has not been done for nearly 100K km, although the intake was cleaned out and a new O ring used). I've looked at a lot of different used oil analysis results for diesels that suffer multiple stop starts and time at idle, that tends to foul up the exhaust system more than normal. The ones where the owner deletes the EGR, show a spike in both Iron, Aluminium and Chrome from the top end, although it's not much of factor with big rigs that use a full pre heat system.

Letting the EGR block up is also bad news, but all it seems to do in oil terms is increase the insolubles figure slightly, from increased blowby.
If you want to keep an EGR clean, just use top quality fuel (Or DYOR on good fuel additives) and try to get some motorway time every month to burn out the cold start deposits. Using a direct feed purge to clean the injectors of gum and using a major brand full synthetic that contains a lot of detergent additives will help keep the rings clean, as compression is also a factor in Carbon deposit terms. Shell Ultra, or LM Synthoils are both better cleaners than Castrol Edge, as they use far better base stocks that are natural solvents. Mobil 1 HC synthetics also clean well.

Oddly enough if you want to improve the main block life of a diesel, one real good extra is a simple stick on sump pan oil heater. The cost of the electricity might be the same as the fuel saved, but they are real good news, because about half of all main block wear occurs when an engine is first cold started. If you dodge cold starts by heating the oil (Full block heaters are better, but more expensive and can be difficult to install), it can easily half the warm up time and get the heater working faster, which is great for the toes.
Such pre heaters can increase the main block, battery and alternator life by around one quarter if used on a daily basis and are fitted as standard (Full block heaters) to many emergency call out vehicles in Germany, doctors cars in particular, like one top of the range Audi near me, that is parked on the pavement when the owner is on call and kept fully warmed up including cabin heat, so the doctor can just floor it immediately and let the traction control deal with the consequences.
He did admit to killing the neighbours cat last winter, which understood less about cold starts than the average boy racer. Poor thing thought it had found a warm dry spot to sleep and finished up with Conti winter tyre tread marks instead!

PS: There are a lot of confusing EGR related junk articles around, partly because of early model EGR systems that did not work too well and companies selling related parts, but as far as I am aware all Volvo engines were designed with EGR units in mind, whereas some older GM and Crysler engines were not, even a few early VW diesels ran into some issues with valves blocking faster than expected.
I just look at facts not press or biased articles and I've seen enough UOA results of before and after deletes to know it's bad news to fiddle with what the Volvo Gods designed.
The data I've seen for pre heat use is for trucks only so far, but I will try and get some figures for my own diesel (Wolverine 250W pad) this winter, because the 25% improvement for Canadian trucks and German diesel cars might be effected by the use of GTL or G4 group synthetics that were not used by those vehicles.

(Copy ZF/MTU English tech forum file)