Interesting and lively dialogue here, for sure. I'm going to take a bit of a tangent back to the original topic to share my experiences with the GDE tune for those who might be interested in doing it:
- I bought the tune almost three years ago with 72K on the Westy
- I've driven about 50K miles since installing the tune
- Purpose for the purchase was to reduce risk of EGR problems, reduce soot (added longevity), increased efficiency, and reduce possibility of SKREEM issues
- Original tune files provided had a revise shift map. I found this to shift too soon and did not like the feeling of lugging the engine. Upon conversation with GDE, they provided replacement tune files that returned the original shift map. The result was the feeling of the original Westy with an added boost of power when needed
- Since the tune, the Westy seems to maintain highway speeds (~65 MPH) more easily and with less strain
- MPG has increased between 1-2 mpg based on my records. Whereas I used to average mid 16's-18, I now typically average high 17's to 20. This excludes the times we tow a trailer.
- I have an Ultra Gauge and watch stats while driving. I downshift when the load goes above the low 70s. I watch temps and they are never a problem. The hottest I've seen is around 205 F on some long steep passes. I do not push it hard up hills, always keeping in mind that the Westy is a super heavy vehicle pulled by a little 5 cylinder diesel engine.
- I use a cetane boosting "cocktail" that sometimes varies depending on what I run out of. I don't know how much it works, but it does seem to result in more quiet operation on the highway, so I presume it is doing something. I also try to stick to higher cetane diesel brands.
- Apparently there are versions of the OM647 diesel in our Westies in other areas in the world (New Zealand?) that were sold without EGR, so that may be some sort of endorsement
At the end of the day, I am satisfied with the upgrade. I would venture to guess that longevity is probably not going to change much with/without the tune, as it has more to do with the way it is driven/maintained than anything else. There are stock T1N Sprinters out there with over a million miles on them.
Would I purchase the GDE tune again? Probably, as I do like the added power and MPG, the added simplicity by eliminating the complexity of two systems, and I am comfortable with my calculation (so far) that the risk of resulting problems is lower than the risk of problems with the EGR and SKREEM.