Dear Tom and Ray:

Is there any way to test a car interior for carbon monoxide or other deadly fumes? I have to leave a window partially open when I use the air conditioner or heater. On trips of 100 miles or more, my dog and I become ill. I have had the a/c checked out The smell is like burning oil, but the oil level stays the same.
Cora

RAY: It's about time you wrote, Cora. We got a letter from your dog a month ago!

TOM: Actually, Cora, I don't think it is carbon monoxide. If it were carbon monoxide, you wouldn't smell anything. That's what makes it so deadly. You don't even notice it until it's too late.

RAY: I'll bet it IS burning oil that you smell. There's probably a small amount of oil leaking from your valve cover onto the hot exhaust manifold in your engine. And the fumes are being carried into the passenger compartment by the ventilation system. And that smell WOULD make you sick.

TOM: And the oil level could stay essentially the same because it doesn't take much oil at all to make a whole lot of smell. A few drops is all it takes.

RAY: Have your mechanic look for signs of burning oil on the manifold. If the valve cover is leaking, its gasket can usually be replaced for a lot less than $100.