1) Why would you use Quaker State Euro in your Grenadier? It does not meet the specs for the Grenadier (per manual 0-20W, ACEA C2, BMW LL 17FE) and doing so may not cause your engine to blow up but it could jeopardize your warranty.
2) How do you know your oil filter is ok. A properly functioning filter will remove particles too small for the human eye to see. Do you do oil analysis in every change? (BTW, I think your 5k interval is a good investment.)
Quaker State® Euro Full Synthetic motor oil is specially formulated in 5w-40, LX 0W-30 and L 5W-30 viscosities to protect today’s European vehicles.
www.quakerstate.com