Toyota 2AR

The 2.5-litre four that replaced the 2AZ in the Camry and RAV4, and in 2AR-FXE form the petrol half of the Camry and RAV4 hybrids. All-aluminium, chain-driven, with an oil-cooled piston arrangement and — importantly — a revised piston and ring design specifically addressing the 2AZ's oil consumption.

That lineage is the most useful thing to carry into a diagnosis. The 2AZ's oil-consumption and head-bolt-thread failures are the first results any search returns for a Toyota 2.4/2.5, and neither is a 2AR pattern. Confirm the engine code before repeating that history to an owner or pricing a thread-insert repair.

What it does show at high mileage is ordinary: water-pump weep, ignition coils, and carbon on the throttle body. The hybrid FXE version again runs the Atkinson cycle inside a hybrid control strategy, so idle, start and charge complaints on one are questions about the system rather than about the engine.