I'm coming up to my next oil change on my 2018 Audi S4. I got the first oil change at 7.5K miles as comes free for the first one. I performed UOA on both the FF and sampled the second one without draining at 4.5k miles.
I'm settling on 7.5K OCI as I feel comfortable with this. Maybe I will extend it out but for now would like to stick with it.
I am currently looking at either sticking with the Castrol LL IV FE that I've been using or possibly switching to Motul or Ligui Moly Top Tech 6200. I have contacted Mobil 1 but it does not appear you can get their ESP 0W20 in the US just yet.
The reason I may want to switch is that I use about a liter of oil for the 7.5k interval. I know that's pretty "standard" now but I have other vehicles that don't use any oil. A person on the Audi Forums claimed they used oil with Castrol but did not use any when they switched to Motul.
I know the motor is still young and breaking in but I guess I'm not too thrilled with the wear numbers. Before someone suggest running something like Mobil 1 0W40 or Castrol in 0W40 I would like to follow the warranty guidelines and use 508 as much as I would love to use something else. This may change in time but for right now want to stick with 508 oil.
I'm leaning with using Motul as someone had a favorable experience with it. It is a little more expensive then the Castrol. Since there are no 508 spec oils on shelves they must be ordered. The Castrol with a filter is roughly $90 for 8 liters. The Motul is around $110. The S4 has a capacity of 7.25 liters (7.7 quarts) with the remaining .75 liters used for "top offs". No idea how much the Liqui Moly would run me.
Last thing I have feeling the TBN number for the FF was out of error. With that said it is a little disconcerting that the TBN was at 3.3 with only 4.5k miles on the oil. I'm thinking 7.5k OCI is ok since I use almost a liter of makeup oil. Any concerns here?
If it were up to you what would you choose and why? Looking forward to your guys opinions!