Very interesting, where I feel long oil changes can cause problems is the actual fleet lease companies themselves, how can I trust that they haven’t insisted that the dealer doing the service must put cheap oil that’s not right for the engine in the sump, the same people that will not allow a garage to replace the diesel fuel filter, only for the vehicle be brought back a week later as the filter was clogged causing a lack of acceleration, or only willing to replace one shock absorber that’s leaking fluid, not the pair, or telling tyre retailers to fit the spare and put the worn, illegal one back as a spare, all true experiences, this is the biggest problem to me.