Re: 240 degrees: I would be a bit concerned about 240. The engine should come up to 230 degrees while its at idle... and only because the computer lets it. It's quite capable of bringing it down lower rather rapidly. If it's reaching up to 240, that's not a good sign... that would indicate that it's struggling to keep cool and not just getting up that high because it's programmed to.
As I understand it, the engine will emergency shutoff at 250 degrees. And some say that this is already too late. So there's not much safety margin there.
This is one reason why quite a lot of people reprogram their computers or otherwise convince their cars to turn on the fans sooner and keep the temp to something more around 200.
Anyway... the typical cause for temperatures above 230 is leaves stuck between the condensor and radiator. This area is rather hard to reach and difficult to see. And it gets full up with leaves which block the radiator. It is possible to diagnose this problem using a flashlight to peer between the slats from certain angles.
Alternatively, your secondary fan may not be functional. But it's usually the leaves.
Also... you should check your under the front of your car commonly... any time you see the temperature spike at all... and every time you stop at a gas station. These bottom feeders suck up plastic bags about once a month, in my experience.
Re: Mobile 1 oil: Your question should really be a seperate thread. But I'll comment anyway. Later years of Corvettes went to Mobil 1 as the factory fill. They did this in part so that they could remove the oil cooler and thereby save weight and space. The synthetic oil is the only variety that can withstand this application. Just think about that for moment. Regular oil isn't rated high enough to survive in the later vettes. Wow. Mobil 1 is great stuff, and I would highly recommend it. The cost of oil... even expensive oil... is utterly insignicant compared to the cost of corvette repairs. Why play games seeing how cheap you can go before it has a problem?
I've read articles and claims of people running cars on much less than ideal oil specs and change intervals... and heralding their successes in still having a car that runs. Obviously good oil isn't needed, and manufacturers are just trying to burn you for money by recommending shorter change intervals than you could possibly get away with. *rolls eyes* I just don't understand that attitude myself. Oil can't be clean _enough_. The cleaner and higher quality it is, the longer the engine will last. Plain and simple. There are diminishing returns, sure. Absolutely. But I want my vette to last forever. I'm not just trying to make it last for a couple of years until I've run it into the ground enough to sell it for another one.
And I have definately noticed that all the people that I know who change their oil religiously every 3,000 miles... seem to hardly ever have any engine problems. Funny that.
PS: Dunno why I've gone ranting on this. Not angry or anything... just talkative I guess. I've been quite sick today and I'm stir crazy. Anyway, I hope there some useful information up there somewhere.
- Skant