Hi,
I'm new to these forums, but just wanted to give a little input on the subject of operating temperature and it's effect on ignition timing and related things. I'm currently running my '98 Ram 5.2 with the largest available radiator, no thermostat, and water only + a racing additive & water pump lube. This results in running temps between 129 degrees and 147 degrees, depending on the ambient temperature and driving conditions.

Now, before I get flamed here, let me explain that i do know the engine is supposed to reach a certain temp in order for the computer to lean out the fuel mixture and things like that. I have a friend who is very knowledgeable in auto electronics and computer systems, and without going into the lengthy explaination of the steps involved (not all of which I fully understand) he has set up the sensors to 'fool' the computer into thinking the engine is fully warmed up. I do know that the way he set it up, my fuel mixture leans out within 20-30 seconds of startup. Not really a problem living in south Florida. I have also recalibrated other systems accordingly, such as using spark plugs several steps up in heat range since the engine runs so much cooler than stock. But most importantly, this has allowed us to advance the timing 4 degrees while still using 87 octane pump gas. I can tach her to 6000 rpm's in hot weather with no noticeable ping or knock at all. I have removed and examined the spark plugs, and they look as they should in an engine with correct heat range, fuel mixture and ignition timing. The timing advance makes the truck feel more responsive, especially at light throttle blips.

I have heard people talk about disadvantages of running too cool as well as too hot. From my personal experiences however, I'd rather lose a pony or 2 due to the oil viscosity being a tad high, and reap other benefits I have noticed over the years of super cool running engines. It is true that most of the vehicles I have set up this way were older, carbureted, non computer controlled vehicles, and I do not know if it is possible to set up all modern engines/computers to run this way. I'm not a master mechanic, just a gearhead who has studied engine rebuliding and built high performance motors since I was around 16. I'm in my later 40's now, and have always run my engines as cool as possible, and here are some of the biggest differences I've noticed, just so folks can draw their own conclusions.
1.)It keep an engine incredibly clean. Oil and oil additives do not break down at temps less than 140 degrees. I have broken down several engines with between 275k and 300k + miles on them, and there was none of that brown, baked on varnish on parts inside like oil pan, rocker arms, valve springs, heads. With a little spray cleaner, the parts looked almost new.
2.) It allows much more timing advance without using higher octane fuel. We have even built supercharged engines that ran on pump gas without a timing retard, and without an intercooler because the engine ran so cool it wasnt knocking.
3.) It seems to cause the engine to last much longer. This may be subjective, however, I have NEVER blown an engine. And I don't baby my vehicles. In fact, I tend to beat them like a rented mule most of the time. I have had several hot rods and high performance vehicles, as well as some stock daily drivers too, that I drove for well more than 300,000 hard miles, and even with all that mileage, they always survived being tached to the redline and asked to do the impossible. Most of my engines I retired or rebuilt simply because they started burning oil because the valve seals or rings started to go because of the high mileage. I routinely have vehicles far longer than anyone else I know that are never in need of major repairs. Of course i am a stickler for maintenance and tune ups, but still, the major difference to me is that my car is running at 130 degrees on a 97 degree day idling in traffic, while most of theirs are running 215 degrees + in the same situation.
4.) It gives you a lot more leeway in case of an overheat situation. In other words, a temp gauge in one of my vehicles showing a reading of 180 degrees would warn me of an extreme cooling system malfunction and give me time to pull over and shut the vehicle down while still being far below the damage threshold for the engine. This did happen once when an object went through a radiator on a truck I owned while running off road. When I saw my temp rising from the normal 128 or so to around 180, I shut the engine off and found that i had lost about half my coolant, yet was still running cool enough not to have to worry about overheating damage.

So anyway, just my 2 cents, and you can draw your own conclusions.
Dave