Originally Posted By: dnewton3
5% is the cautionary limit. Not an assurance of harm, but the time to look for escalation of wear. If the wear metals (rates) are OK, then I'd not worry. However, I'd not want fuel to go above that during the OCI. If you're historically seeing 3-5% fuel, and the metals are fine, I'd stick to the OCIs that are giving you the desirable wear results. If it's the IOLM you're following, then great.
The 6.7L PSD seems to have a fairly large variation of fuel from unit to unit. Not much rhyme or reason to it. Typically lots of idling will cause the fuel up from regens. Why yours is high from good long runs is a bit of a mystery. But as long as it's not harming the wear rates (and it does not seem to be doing so in the least), you'll just have to consider it normal.
Thanks Dave. The iOLM has never indicated to change the oil (not sure what its recommendation would be), but 7.5-8K would be "my" OCI limit at present since the dilution is keeping me cautious. The thing that is bothering me the most is something seems to have changed since I had (what I consider to be) decent fuel dilution rates until around 32K on the truck and then things went a bit awry.
The MAF failed during the OCI that had 5% so I backed the OCI down a little to see what would happen to the dilution rates and they went down, but not back to less than 1% as before, although on a per mile basis the last OCI has less fuel dilution than the previous two. I think something is still happening, just not sure what and I suspect the dealer may be the only recourse. Regens on the 6.7L are fairly long (at least on my truck) and I am sure they are contributing, but something sure seems to be "off".
Code:
Vehicle Mileage 44,144 37,027 32,700 26,550 21,330 14,470 10,692 6,234 1,570
Oil Mileage 7,117 4,327 6,150 5,220 6,860 4,018 4,458 4,664 1,570
Fuel Dilution 4.00% 3.40% 5.00% pre>