I took three different oils that I had kicking around and poured a small amount of each into like containers (clear). The first was Pennzoll Multi-Grade PB 5W30 - quite dark brown, translucent. Chemical odour slightly sweet. The second was Formula Shell 5W30 - colour of light honey, much lighter than the pennzoil and transparent. Sharp odour, smells like fish oil. The third was Motul 5100 10W40 - Darkest of them all, blackish green tinge, very slight, translucent to opaque. Oh, that Motul smell, it's put in for marketing puposes so it's irrelevant. If your curious pick up a liter. So, what can be gleaned from this? I was curious if the colour indicated the base oil used, since high quality base oil should be white and clear. Obviously Pennz and Shell have very different add packs, what could be the difference? The Motul was a Red Herring in the bunch I would have thought it would be very clear, being a synthetic or blend or whatever it is.