Right, I've seen a few posts about this oil and some say it's the same as halfords (which might be cheaper?). It's not supposed to be a fully synthetic even though it says it is. Oilman had a post somwhere about this. So, is it any good for a 58k 172 for fast road, no track? 5l will set me back £23. Do I really need a proper fully synthetic like silkolene or will this be fine?