The Owners Manual doesn't actually specify what type of oil, only that it should API Service SE, SF, SG or higher, so in theory you could use a mineral oil that meets these specs, but I doubt anyone would recommend you do so. Up until my last oil change I always used semi-synthetic and made sure I did a change every 4,000 miles. Having read that the owner of the 220k Gen1 regularly used fully synthetic I thought I'd give it a go last oil change and I won't be going back as I recon the engine feels smoother and happier with fully synthetic, and if it helps prolong engine life I'm all for that.