Toyota and spin control . . .
Toyota has a few more skeletons in the closet than just the engine sludge issue. One of their most popular engines from the late '90s through about 2007 was the 1zz-fe. It's a 1.8 liter twincam long stroke engine, with the 2zz being the short stroke performance engine of the same size but different design. The 1zz was built in Japan, Canada, and the US, and used in the Toyota Corolla, Toyota Matrix, Toyota Celica, Toyota MR2, Chevy Prism, and Pontiac Vibe. Engines built before late '02 were usually OK, but a small but significant number became oil burners because there weren't enough oil return holes in the pistons and some of the blocks were weak and the bores went oval - this combined with low friction rings to make the oil control rings ineffective. Like the Northstar, this is an open-deck aluminum block engine. For most cars the oil burning was annoying, but like GM Toyota's official standards for oil consumption are pretty lax so they didn't warranty many.
On one car the problem was sometimes catastrophic: the little mid-engined MR2 two seater. This was a limited production car, with US sales starting at about 7500 cars in 2000 and ending with less than 800 cars sold in 2005. Toyota decided to emission certify the MR2 as an Ultra Low Emissions Vehicle, which meant adding two pre-catalysts to the normal exhaust catalytic convertor. Because of the mid-engine design, the only place to put them was in the exhaust manifold, inches from the exhause ports. Catalytic convertors use a ceramic honeycomb matrix to hold the metallic compounds that treat the exhause gases, and these ceramics are very, very hard but also brittle. They cannot tolerate oil, and will break up into tiny abrasive pieces if exposed to oil - this is a known fact. There are many documented stories of early MR2s which all of a sudden lost nearly all their oil, and often spun rod bearings as a result. Toyota mostly blamed the owners for not checking their oil and refused warranty coverage. A few owners got lucky and caught the problem before spinning a bearing and got covered for their new engines.
The mystery was, why did low mileage engines all of a sudden start using huge amounts of oil without mechanical failure? It took a lot of detective work amongst owners but eventually the cause became clear. All early MR2s have manual transmissions, and being sports cars Toyota gave them short gearing so they tend to rev high. The 1zz has variable valve timing, and at high rpm the timing provides a lot of valve overlap when both the intake and exhause valves are open. This is good for both power and emissions, but also results in some exhaust being sucked back into the engine. Once an MR2 engine started buring oil, the pre-cats broke up, and if the driver revvved it under load the little ceramic bits could be sucked back into the engine where they just destroyed the rings and bores. Toyota actually had to 'fess up to 1zz problems on MR2s in Britain, but here they denied it while quietly warrantying lots of engines caught before the bearings spun. Starting in late '01 and going through most of '02, they made running changes to the 1zz, first the rings, then the pistons, then the block assembly, then the oil pump. No manufacturer does this in a piecemeal fashion unless they're running scared. The fix seems to have worked, as very, very few '03 or newer cars have been affected with this problem.
I'm not posting this to rant on Toyota - most of their cars are very reliable indeed. My mother's eight year old Camry XLE has virtually all options available, including power everything, climate control, and the sometimes sludgy V-6, but in over 100,000 miles it has had exactly two failures: a seat belt retractor cover, and a slight leak from the rear main seal. The latter could have been expensive but was covered by warranty. The 1zz problems are atypical, but prove that Toyota is quite capable of making big mistakes.
