Gonna buy a Mercedes S400 CDI (yes the big one) diesel that gets 34 miles to the gallon, lol. Or, get the E400 that gets 37 miles per. 

Now, if I was really creative, I would take the Volkswagen Turbodiesel engine (that gets 45 per gallon), and put it in a Prius chassis.  Imagine what the Prius would get then! 

I've started turning off my car while I'm in the drive-through, ever since I read that 10 seconds of idling and turning the car on again use the same amount of gas.

citybeat: Remember that the vast majority of wear and tear on an engine happens when it is started, even if it's off for a short time. I would suggest that the wear and tear will eventually cost you much more in repairs than any potential gas savings. Your best bet is to put the transmission in neutral when stopped. That will save gas, your transmission and your engine. Starting in 2010, GM cars will have what they're calling "neutral idle technology" which will automatically put the transmission in neutral when you stop, and reengage drive when you release the brakes.

As for drive thru's, avoid those too. Better for your health!!!  Cheers.

I'll bet that wear and tear is minimal in this circumstance, as the oil hasn't had a chance to drain.  More wear and tear on the starter motor, sure.  I'll freely admit that cars aren't my area of expertise.

But you're right about avoiding the drive-thrus.  Better still, avoid the fast-food joints altogether.

The oil is only part of the problem. Modern cars are using 5 weight oil for better MPG. That stuff drains quickly. 

Worse than that is the fact that when an engine is at operating temperature, and is shut off, the core temperature and cylinder heads actually get much hotter for a short period of time. When this happens, compression increases, which places the compression ratio much too high for regular gas. The high compression in addition to hot spots in the form of carbon deposits will cause pre-ignition. Since there is not enough time for the computer to detect the pre-ignition, and there's no usable data during start-up, a rapid, violent bout of pre-ignition (.2 to .5 seconds) will hammer the engine during the first few combustion cycles until the cylinders, fuel, and air reach the proper temperature and fuel/air ratio to run normally, as adjusted by the computer. You can rarely detect it, but believe me, it's happening. That causes lots of nasty transient stuff that just isn't good. That's one reason why delivery vehicles have such a short life span, while long haul highway drivers last forever.

Note: Diesel engines do not have this problem.

I have a Pruis, which shuts off and starts back up by its self. Once in a while, on hot days when I'm stuck in traffic, crawling along, the engine will start up and shake/shudder badly for about half a second. That is exactly what is going on. They all do it, but most people never notice. Being a pilot, and relying on engines for my life, I pay attention to every squeak and shudder they make. Can't help it.

I concede your superior knowledge on the subject.  But I still suspect the oil doesn't drain that much in the short time we're talking about, and having the horses jump up and down in place with little-to-no ventilation airflow can't be good either.

Got to admit that I was surprised to find my Ion recommending 5W30, as I'd been accustomed to running 10W40 in my engines.

You are right, random, the oil will drain back into the case in a few minutes, but a sufficient coating of oil remains on the pistons and cylinder walls for several hours or more, and begins circulating very quickly on start-up. The oil is the least of our worries!

I can't claim any "superior" knowledge, I'm just kind of an engine nerd. I used to tear them down for investigations, so I learned quite a bit about the nasty things that happen internally. If you could see some of the stuff I've seen...