I felt the same until I realized how much crap the egr was putting into intake theoretically. I have not had mine off but my mileage had dropped since 72k when I bought it. Only thing left that makes sense is air flow restriction. Will see some day.

But mainly being able to use a better protecting oil is my main reason As proven by blackstone oil tests. The iron level is considerably less. If course this is with the dpf removed. Which if you look into it you wonder the effect of the major exhaust restriction on the engine. I feel like my truck drives much smoother at higher speeds now.

After seeing all the timing chain failures I want the best protection. And as mentioned the oil is much cleaner when checking on the dipstick so I am sure that factors in also.

I was using castrol turbo diesel 5 w40 which was a 229..51 before and after the tune since I thought it was a good product. Then switched when I had trouble sourcing it to liqi moly leichlauft high tech which is 229.5. That is when I saw better reports. I wish I had sent off the mobil1 5w40 to see how it performed before the dropped it.