steviestevie

Hi all I'm looking at buying an FJ Cruiser with the V6 1GR engine. The vehicle I'm looking at skipped a service 4 years ago, and so did 20,000km without an oil change. It's since had 3 services on schedule. I'm concerned about permanent engine damage caused by sludge due to the missed oil change. If I get an inspection done by a mobile mechanic, will they be able to identify whether there's any long term damage? Or, is it not possible to tell without tearing down the engine? Thanks for any input