Tom says: "I also have a car with the red 'dex-cool' and I don't know what to do there." _________________________________________________
I've seen some ugly stuff with GM Dex-Cool(R). If I had a GM product, I'd flush out the Dex-Cool and either put in regular green and change it every year, or put in Toyota Original Red, a product for which I know of no issues. I've thought about putting Original Red in my Taurus, but I've got such good access to regular coolant that I've never done it. But again, I think I'm one of the radicals here. I've not seen any issues with the long-life coolants other than Dex-Cool.
Tom says: "Assuming this 'piston clean' is no more than a bottle of 'complete fuel system' cleaner, how good and useful is any of that stuff?" _________________________________________________
Unless it's got something weird in it, it pretty much can't hurt. But if you've got an engine that doesn't carbon, what's the point. Most modern engines carbon very little.
Tom says: "If you have an automatic tranny (in my case, an '02 Elantra and an '04 Kia Sedona), where the automatic transmission has not had a bad trouble index, would you still recommend a 15,000 mile change interval?" _________________________________________________
No. I think the 30k interval is good. I'm not sure about the Kia, but at least for the Elantra that exceeds the manufacturer's recommendation. I'd do 30k on most cars even if they had a 100k manufacturer recommendation.
Tom says: "BTW, while dealer service departments are only beginning to get into the 'tire' business, should you perhaps add some tire services to the list?" _________________________________________________
I'd say it's a good idea to rotate the tires every 7500 miles or so. For about 13 years, I drove only rear drive cars and didn't believe in rotation. I bought new tires two at a time and put the new ones on the rear for good bad weather traction. As the fronts wore out, I'd move the rear to the front and put two new tires on the rear. But with my first front drive car, I learned this was a bad plan. I had to buy four tires. The fronts wore out quickly (because they were on the drive axle), and the rears lasted only a little longer because they were feathered down to where there was no tread in spots. Since then, I've bought four at a time and kept them regularly rotated with much better results.
As for other tire services such as balancing or replacement, I'd recommend them only when needed due to vibration or wear.
We do tire work here, but anything involving tire replacement is very awkward because departmental management doesn't really want the hassle of pricing and procuring tires. Our 15k and 30k maintenance services include a wheel balance, but I think it's overkill to do it that frequently.
And, Tom, thanks for your posts, too. They're intelligent and clear, and most importantly, I almost always agree with them. :)