I moniter the air pressure in my tires through the DIC TPMS. When I picked up the car from the dealer, all 4 tires had 30 lbs of cold pressure. I have the car 5 months and I noticed that the front tires held the pressure at 30 lbs., but the rear tires have dropped to about 27 lbs. It does increase as I drive, but I find it unusual that the rear tires, which have less weight over them, have had a decrease in pressure. What could be the reason for this?

Also, at what pressure would the low tire pressure warning message / indicator light turn on?

I don't know if you are serious about trusting the DIC readout but I've been checking my tires with a tire gauge every couple of months. Since tires can't be made completely airtight, they will to go low over time. Your rear tires probably happened to be more susceptible (rotate them to the front and see?). I think the TPMS warning threshold is ~20% loss from nominal and thus the sensor aren't meant to be that accurate.

That happened to me about a month ago. I agree, rotate them to the front and it should be fine. The TPMS is not all that accurate. I live in Louisiana so I have to monitor my tires A LOT!

I'm not sure about the accuracy of the tires. My printout says my front left
and rear are 2 psi under. Does'nt look bad when I look at it.

It also said I was averaging 35 miles driving pr day. I didn't think that
was correct so I calculated all the places I go during the day. Since I'm
retired it's only the same few places - the gym, the pool, the store, and
the bank.

After calculating the printout was exactly right so I'm assuming it's
right about the tires.

The printiout says I should check the oil at 8,000 and that looks about
right too.

Great features.

That happened to me about a month ago. I agree, rotate them to the front and it should be fine. The TPMS is not all that accurate. I live in Louisiana so I have to monitor my tires A LOT!

Make sure when you rotate them you reset the TPMS.

The printiout says I should check the oil at 8,000 and that looks about right too.

Err, the OIL LIFE percentage is derived and keeps track of the useful life of the oil before a change. It has nothing to do with the oil level which should be checked much more frequently (especially before the first oil change).