Sludge can build up in the engine because Toyota did not recommend frequent enough oil changes. Lexus will sometimes offer a discount on cleaning the engine if necessary. Owners who changed their oil every 3,000 miles did not experience these problems. This sludge build up can lead to excessive oil consumption.Google+
Car Problem Reports
Toyota Highlander Sludge Buildup on Engine Due to Infrequent Oil Changes
Toyota Highlander Problem
Engine Affected: 3.0L V6
Visitor, 2002 Toyota Highlander, 3.0L V6, 42,312 mi
3 quarts of oil in 500 miles, so much for toyota reliability. I sould have bought another Ford.