Use an LL-01 approved oil. Viscosity won’t matter much for leaky valve stem seals. I did have some success with ATP AT-205 Re-Seal in my 4.8. It’s far from your traditional “thick goop” oil stop leak additive. It’s actually water-thin, but it stopped mine from smoking. I still consume about a quart every 2,500 miles which is normal for many cars.



Some LL-01 options:
Castrol EDGE 0W-40 and 5W-40 (available at Walmart)
Castrol EDGE 5W-30 A3/B4
Liqui-Moly Leichtlauf 5W-40 and Special Tec LL 5W-30
Motul 8100 0W-40 and 5W-40

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2007 E70 4.8i