[BillG]

I wouldn't be too concerned. The oil pan holds the worst of the worst oil in the bottom half inch or so. If you really wanted to "flush" it out, you could always put the plug in, pour in half a quart, then pull the plug again and drain that out. That said, if you aren't getting lifter noise at cold start (hard to do in FL, I imagine), I probably wouldn't put any money into an engine flush. Back in the day, you would get a beater that leaked a little oil out of the rear main. You'd add a quart per week. Every 3 months, you spin off the old filter and spin on a new one. No oil change was required because it was on a continuous change interval.

 

[BillG]

Trunkmonkey: Great idea! I wish I would have thought of using air pressure with a can..its a better idea than mine, as it would not waste clean oil.
What I tried to do (to prevent waste of clean oil) is to "recycle" the oil..its not real dirty like dirty oil, but not completely clean, either, as it has been mixed up with old dirty oil. But it works in an oil can, which I use for lubricating hinges, or anything that needs a few drops of oil. Sure, WD40 spray has some advantages to "the old fashioned oil can" you rarely see mechanics use any more, but there are advantages, too, to the old fashioned oil can, we used often on the farm. Heck, nowadays, mechanics often dont even know what a grease gun is. My son bought a new Kabota tractor, however, and it has many grease zerks, which need greased frequently..or else. Its rather unclear to me why a tractor would need grease zerks, while virtually all new cars have no grease zerks. They are all "sealed". So, why would a tractor have grease zerks and a car not? We also dont "pack" wheel bearings anymore..which we always used to do. My father told the story of his 32 Ford. He said he ran it to fast on low oil, and it started knocking. So, he took the oil pan off, and took a file and "filed down" the end caps of the bearings (making it close slightly smaller), put the used oil back in, and drove off...no more knocking.
There is some truth to Henry Fords statement that "the 32 Ford" is perfect, no research is needed, you cant improve it. While it has been massively improved in many ways, I actually tried "filing down the end cap bearings" on my 55 chevy in line 6 cylinder that was knocking after I inserted new bearings. I had taken sandpaper and sanded off the grooves on the crankshaft, somewhat, and put it back together. The engine started and maybe ran a mile before, when it threw a rod, you knew it was done. I knew then the old school "filing the bearing caps" to stop your car from knocking was over.

Mostly, they dont seem to rebuild (remanufacture) most engines anymore. Yea, you can still rebuild an old Chevy 327, or even a six cylinder. But, you probably wont get a good result rebuilding your 4 cylinder 2005 Nissan or Toyota. Modern engines are manufactured by massive machines with very close tolerances that is exceptionally difficult to duplicate in many/most machine shops. Engines have become disposable, sadly, and are not designed to be rebuilt.

Tractors have grease fittings because "sealed" is not really SEALED. In the dirty conditions of typical tractor use, dust/dirt/moisture get where they shouldn't and build up in ways that are detrimental. Fresh grease pushes out the contaminants and keeps joints packed and thick. Likewise, wheel bearings which spend 400k miles on flat highways are fundamentally different from wheel bearings that are dragged through mud and water daily. Back in the day, we had a boat trailer from the 60s which hadn't moved since the 70s being cleaned up for use in the early 90s. My dad pulled the wheels, popped out the bearings, and we cleaned them with solvent, then rolled them around in a light oil and then rolled them around in thick grease then finally jammed as much marine axle grease as we could in them. They went from seized to suitable for the road in about 30 minutes.

As for rebuilding, it's not that it's not worthwhile. It's a function of price vs. results. Back when I had a Ford Ranger, there was a guy who had a 2.3L (originally)/135 hp I-4 engine that he pulled and rebuilt into a high horsepower, naturally aspirated beast just to prove it could be done. I've heard of people throwing a supercharger on a 1MZ in a Sienna before too. For the cost, though, you could sink $10-20k into pulling, rebuilding and reinstalling your Sienna engine OR you can spend $6k dropping in a lower-mileage warrantied engine from LKQ or even a junkyard engine from any 3MZ (or 2GR, as appropriate) vehicle. If you happen to live near old industrial areas or car racing localities, and still have machine shops near you and can be without a vehicle for a while, taking a block, getting it bored and decked and getting the heads surfaced, ported and polished, and building the engine for higher performance, if you're doing all the internal mechanical work yourself could be a worthwhile endeavor. However, if you just want a van to drive you point A to point B, you just pull the old, drop in the less-old and go about your business. OR you trade in the van on a push-pull-tow deal and get $3k for a junkyard candidate.