> I am developing a consumer product that will operate in the
> trunk of car.  My ideal goal is to use commercial grade ICs
> wherever possible.

> My concern with Commercial grade ICs is not the upper end,
> since I can't see the trunk of a vehicle approaching much
> higher then 70 deg c, or 158 degrees farenheight.

If you're planning on selling anywhere in the southwestern
US (eastern southern California, Nevada, Arizona, New Mexico,
or west Texas), 70 deg C vehicle sheet metal is a reality.
If you have any low thermal resistance path to your chips,
you may start seeing product failures and returns.

Will you have control over how & where in the trunk the
device is installed?

Another thing to remember, is that most parts are built on
a single fabrication line.  They are binned into various
grades by testing.  So any given group of a commercial IC
will likely have a higher percentage of parts barely able
to function at the extremes of that temperature range.

                                                Lee Jones