That's usually the best method to make sure it's right. Outside during the winter, 2 hours should be enough (assuming below freezing) though. If allowed to get low, air bubbles do become a nuisance though, and either the incline filling method or driving for a day or two are what's needed to get the last little air pockets out. Or a combo of both.

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Olympic Peninsula, WA, USA
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2005 Mini Cooper 100k, British Racing Green/Silver-Black
04/2002 4.6is 140k, Silver/Black-Alcantara *FOR SALE*
1989 325iX 270k, Diamond Black/Black
1984 318i 370k *SOLD* (First Bimmer)
Honorable Mentions: '71 2002, '87 325, '90 325ic, '92 525it, '93 325i, '94 530i