THINK TWICE

Excessive oil consumption is the defining defect of Toyota's 2.4L 2AZ-FE four. 700 federal complaints across the 2007-2011 Camry, 2006-2008 RAV4, and 2005-2010 Scion tC describe the engine burning or rapidly consuming oil -- commonly a quart every 1,000-1,500 miles with no visible leak and often no low-oil warning until the level is dangerously low, which can starve and destroy the engine. The cause is attributed to the piston-ring / oil-control-ring design. Toyota acknowledged it with a warranty-enhancement program and a dealer oil-consumption test (162 of these complaints explicitly describe undergoing that test). The complaints skew four-cylinder wherever the corpus records cylinder count, so this is the 2AZ-FE's problem even on the V6-optional Camry and RAV4.

Check — Pull the dipstick before any test drive and ask how much oil the car uses between changes; treat a quart per 1,000-1,500 miles as a red flag. Look for oil-consumption test results, a ring/piston repair, or a short-block replacement in the service history, and watch for blue smoke on cold start and a low level with no visible leak. Assume you will have to monitor oil between changes.

The 2AZ-FE's cylinder-head bolts thread directly into the aluminum block, and those threads strip or pull out. 33 federal complaints across these windows -- most on the 2004-2007 Highlander, where it is the engine's signature failure -- describe head-bolt threads stripping, head bolts pulling out, a resulting head-gasket leak, coolant loss (sometimes into the cylinders) and overheating. Owners are typically told the only fix is a new or rebuilt engine, often just outside warranty. The complaints skew four-cylinder wherever cylinder count is recorded, so this is the 2.4L four's failure, not the V6's.

Check — On a cold engine check the coolant level and condition, look for unexplained coolant loss with no external leak, white or sweet-smelling exhaust, and any history of overheating or head-gasket work. A documented head-bolt/thread or head-gasket repair (or engine replacement) is reassuring; unexplained coolant loss or overheating on a 2.4L example is a walk-away.