when i drive on the highway for protracted periods such as an hour, my lungs will burn for a day or two afterwards. the HVAC is all set to off when i do this and windows are closed. note that this car doesn't have recirculating air.

the center dash feels uncomfortably warm,... if it was any hotter it would be painfully hot.

after a fuel pump replacement this past week, the dealer noted that there is a very small oil leak but they won't say precisely where. the oil lines are dirty but i don't know whether that's a red herring. the oil line which is farther to the left if you are sitting on the driver's side is wet with oil at its lowest point and has plenty of dirty dry oil near the crimp sites on both the hose and metal. the oil line which is just to the right of that (towards the passenger) is not wet and is a bit less dirty.

2004 chevy blazer, 172000 miles

well cared for, major portion of life in a garage (but not entirety of life). regular oil changes, fluids changed etc.

what is wrong with my vehicle? what will this cost to fix?

 

Driving in a sealed environment with no air circulation doesn't seem like a great idea. Have you checked or had your vehicle checked for exhaust leaks? A cracked head or rusty exhaust could leak exhaust that could possible infiltrate the cabin of the vehicle, and without any fresh air circulation you might see negative effects.

My recommendation is to use at least some air circulation (fan on low).

If you think the vehicle may have an exhaust leak, have it examined and tested by a qualified mechanic.

 

The highway air is intolerable in its own distinct way

 

Still, highway air should not cause the irritation you describe. That are symptoms similar to asphyxiation by exhaust gasses.

I'm with ElBeautor, by checking the exhaust system. Also because you mention a hot dash, or maybe even the lower console is hot?