In the United States, Toyota has caved in to a small but vocal number of customers who have been complaining that faulty engine design, rather than, as the car maker maintains, a lack of maintenance has caused engine-ruining oil sludge.

Toyota’S new so-called Special Policy Adjustment (SPA), good for a year, will cover repair costs for owners who can produce “reasonable evidence of regular engine maintenance”, the company said in a statement.

Reasonable evidence, the magazine Automotive News said, in a story carried on its website, was proof of one oil change a year.

Toyota said that oil sludge, or gelling, as it refers to it, tends to occur due to three factors.  Changing motor oil less frequently than the recommended interval is the primary cause along with short, stop-and-go-driving cycles and cold weather climates.  Symptoms of oil gelling include blue smoke coming from the tailpipe and/or excessive oil consumption, which may cause a malfunction light to illuminate.

Toyota said it was offering the one-time goodwill gesture for a year.

“We’re not aware of any cases of oil gelling in properly maintained engines,” said TMS group vice president and general manager Toyota Customer Services Bob Daly.

“The vast majority of Toyota owners, and motorists in general, regularly maintain their vehicles and will never encounter this condition.  But for some, busy schedules, budget considerations or misunderstanding of what constitutes ‘normal’ versus ‘severe’ driving conditions may result in neglecting their vehicle.”

Automotive News cited several Toyota owners who had been denied expensive engine repairs under Toyota powertrain warranties due to oil sludge, despite being able to produce to dealers receipts from independent lube shops.

It cited two independent experts as saying that the concentration of the sludge build-up problem in just two engines – the 1MZ V6 and the 5S-FE in-line four in vehicles built between July 1996 and July 2001 suggested a design flaw or quality problem.

But Toyota denied there was a problem with its engines and said that the change of heart was all about encouraging correct vehicle maintenance and calming owners’ fears about oil sludge.

The company said that letters reminding customers about the importance of keeping up with their vehicle’s recommended maintenance programmes and detailing the specifics of the SPA were sent to owners of potentially affected vehicles beginning this month.

Vehicles involved in the SPA include “certain 1997-2001 model-year vehicles with four- and six- cylinder engines”. Automotive News said the affected vehicles are Camry and Camry Solara, Avalon and Celica cars, Sienna minivans, the Highlander and Lexus RX300 SUVs and the Lexus ES300 sedan.

Toyota and Lexus owner’s manuals stipulate oil changes every 7,500 miles or six months, whichever comes first under normal driving conditions, and 5,000 miles or four months under severe operating conditions.  The 5,000-mile, or severe schedule, should be adhered to if a customer drives on unpaved or dusty roads, tows a trailer or makes repeated trips of less than five miles in cold temperatures.

Toyota spokesman Mike Michels told the Los Angeles Times that 3,100 complaints about oil sludge problems had been received.

“We are talking about 0.01% of the owners,” he told the newspaper from Toyota’s Torrance headquarters. “If this were a pervasive problem, we would have known about it long ago. Quality surveys from J.D. Power and others would have reflected it.”

Michels declined to speculate to the LA Times on the potential cost to Toyota — first-class postage for the letters alone cost $US1.1 million the paper noted — but said many of the engine problems could be repaired by simply changing the oil several times to flush the sludge.

“A valve job might be the most expensive thing. An engine replacement would be very rare,” Michels said in the LA Times interview.