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.
Excess Engine Oil Consumption on Toyota Sienna
Average mileage: 116,750 (50,000–172,000)
Engines affected: 3.0L V6, 3.3L V6
13 people reported this problem
2002 Toyota Sienna - 3.0L V6 135,000 mi, Visitor
when I would accelerate hard getting on to the highway I would hear valve knocking. Also when I changed my oil it would be a little clumpy coming out. I did a little research and found that you can put seafoam in the crankcase. Read the bottle but I put like 4 ounces in the crank case and then changed my oil again in about 300 miles and I have no more sludge and no more knocking. I am getting slightly better mileage too. when I changed the oil after the seafoam the oil flowed well but it was really dirty for only having 300 miles on the oil change.
1999 Toyota Sienna - 3.0L V6 110,000 mi, Visitor
motor suddenly seized up. had to replace entire motor at our own expense
2006 Toyota Sienna - 3.3L V6 50,000 mi, Visitor
toyota dealer want me to do every 5000 miles ,is that ok or no