Toyota engines - the sludge problem

Both four-cylinder and six-cylinder Toyota engines of the late 1990s and early 2000s have been prone to oil gelling or “sludging,” which could affect cars that were only a couple of years old. Before buying a used Toyota of this era, it may pay to look under the valve covers for “sludged” oil. Blue smoke may be one symptom. Many recommend using synthetic oil to avoid the problem.

What causes the problem

In some situations, oil additives are burned off or destroyed; then oxidation occurs and pollutants congregate in the oil, producing sludge and varnish. Originally, it was thought that the oil was being “burned” by excessive heat, but the sludge may be caused by problems with crankcase ventilation, at least in some cases. The problem was not particular to Toyota and Lexus; Mercedes, Volkswagen, and Chrysler have all had problems (Chrysler’s was restricted to the 2.7 V6, and was soon cured) — but Toyota appears to have been afflicted more than any other automaker, and it affected both V6 and four cylinder engines (built from 1996 to 2001).

The volume of rubbish in the engine could plug filters, the oil pickup screen, and oil passages, causing other parts to fail. Toyota extended warranties on affected engines to eight years and unlimited miles, though they originally blamed the owners, and for a time refused to pay at all for engine damage. Mercedes, incidentally, raised their warranty to 150,000 miles after a lawsuit.

Even though sludging was “common,” it seems that only around 1% of cars made had problems.

Here is Toyota's new policy. The moral: keep your oil change receipts (or have oil changes done by a dealer) and use synthetic oil.

Toyota wrote that it "is taking this action because a very small number of customers have reported engine damage from motor oil breakdown, also known as oil gelling or 'sludging,' a result of oil change intervals delayed beyond the factory-recommended schedule. While any make vehicle can suffer from this condition if the oil is not changed often enough, Toyota has initiated this program to ensure owner peace of mind." (This blames the owners for a design flaw, since it doesn't affect earlier vehicles or other engines, and is in fact quite rare on other automakers' engines, and can happen even if you follow Toyota's recommendations on oil changes.)

Toyota continued: "To make sure that customers have absolute confidence in their vehicles, this program will cover repair costs and incidental expenses for which a customer has paid or could incur as a result of damage due to oil gelling for a period of eight years from the date of first sale or lease without a mileage limitation. In addition to the costs of repairs, reasonable incidental expenses, such as car rental, and other out-of-pocket expenses will be covered."

All parts required in service have to be returned to Toyota, or dealers will not get paid. Here is what they need to replace:

• Connecting rod bearings and main bearings
• Oil pump and pickup
• Engine seals and gaskets
• Rings and possibly pistons
• Valve sealts and valve covers
• Entire short block if necessary

The customer needs to pay for any wear items replaced in the process, such as the timing belt (not a bad time to do it) and spark plugs. Consider it to be an opportunity to have maintenance done without small or nonexistent labor charges.