Originally Posted By: UltrafanUK
Nasty case of fuel contamination resulting in rather thin oil. I would move up to an Xw40 AND cut the OCI to 3000 miles.
I would also try using a direct feed injection cleaner fuel additive like Liqui Moly Diesel Purge every time the fuel filter is changed. All you do is fill up the housing with purge when changing the element, that way you can make sure the fuel contamination is just a DPF short tripping issue, rather than gum deposits in the injectors. They tend to form when using cheap fuel and short tripping a lot.
Also if you are stuck with a fuel contamination thin oil issue, use an oil that has both Moly and Boron additives. The alternate approach if you have a stash of cheap oil is to use a major brand additive. I use Ceratec which contains both Moly and Boron Nitride in hexagonal form, although it's not cheap.
not so nasty... the ac delco oil is around 3.1 hths when new, and the engine only requires 2.9 as a minimum.
an A3/B4 C3 rather than C2 would be a step up, but I would (and did) go up to an A3/B4 so the fuel contamination doesn't result in a serious watering down of the additive concentrations. Don't forget that any moly or boron you add (esp hexagonal-colloidal) adds to the SAPS level in a serious manner.