After reading some of the other reviews of the Sienna I consider myself lucky. A lot of folks have had misfortune with these and I am happy to say that I am not one of them. In fact, I had no idea about the sludge problems with these things until about a month ago. I never received a letter from Toyota or anything.
I bought this van brand new from a friend who is a salesman at a local Toyota dealership in August of 2001 as a 2002 model. It was the first and only new vehicle I have ever bought, and only did so as he gave me a good deal (about 3k under sticker, yes it was that good). So I guess that I did not experience the pain-in-the-ass dealership experience a lot of people seem to complain about here.
92,000 miles later I still have not had a single problem with this van. Never left us stranded or anything. Up to this point it is the most reliable vehicle I have ever owned. And I have owned mostly toyotas throughout my 40 years of driving.
This is NOT WELL MAINTAINED. It has been neglected in terms of regular maintenence. The last oil change we got for it was after 7,000 since the previous one and most of them are every 5,000 or more. We only use the low grade 10w-30 stuff and the normal filter. We have only gotten a tune up twice and not from the dealer (although it could use one now). We rarely clean it either. We wait until it gets real gross inside or out to clean it.
Our previous van was a 1992 Chevy Astro AWD Shorty. It was reliable and lasted us 200k miles, but had more problems than the Sienna did at almost 100k miles. It was a good van, but it just kept on nickel and diming us to the point were we sold it and bought the Sienna. Just one thing after another past the first 85k. Chevy's don't tend to age as gracefully as Toyota's do (seems like as soon as the warranty goes out all the problems start to happen). The front seats in the astro were way more comfortable than the Sienna. The Astro had AWD and got terrible gas mileage, but was very good in the snow. I can't say the same about the Sienna, doesn't seem to do so well. Luckly we only see snow less than five days a year. The sienna is so much smoother, quieter, faster, and handles way better than the astro ever could. Kind of unfair to compare the two, but it helps show how much improved this is over the chevy. The Sienna is just so very well built, the quality is excellent. Quite unlike caravans or ventures or windstars of the same year (pieces of crap)
Bottom Line: No matter what we do or don't do to it, it keeps on keepin on and never gives us a moments trouble. I guess we just got lucky, unlike a lot of other Sienna owners did. I expect this to last for a very long time.
I've never gone wrong with a Toyota, and I doubt I ever will.