I am shopping for a pre-owned vehicle. I'm probably gonna go with a large SUV (>6,000lbs GVW), so that I can write it off taxes. I've got my eyes on a loaded-up 2017 Ford Explorer. It's a beautiful vehicle, but it has 49k miles, plus it has twin-turbo V6 engine. I've been studying up on these engines and the biggest EXPENSIVE issues seem to be failed turbos and stretched timing chains (all of which use engine oil for lubrication). So my whole buying decision really hinges on maintenance. If oil changes were extended to 10k (or more) then the odds of major engine work being needed are greatly increased IMHO. I asked the dealer if they have service records, but they don't have maintenance records for this vehicle. Do any of you guys have ways that you use to determine if oil/filter has been changed adequately? I will usually take off filler cap and look/smell, but that isn't really getting inside. I'm looking for any other ideas. Thanks!