My daughter will be in the market for a newer car this summer. She is interested in another Camry or a Lexus ES. Her budget will take us to late '90's/early 2000's, which is during their era of sludge-prone engines. Her budget will also take us into higher mileage cars as well. My question is this - if an engine was going to sludge because of the engines design or someone following a OCI longer than what they should have for this engine, when would the engine problem have shown itself? If one of these cars has 130K - 150K miles on the original engine, would it be safe to assume this engine was either well taken care of or not a problem engine? If I purchased one of these cars, would it best to do an Auto RX cleaning regardless?