So, it's still winter here up north. And I thought I was doing the right thing by going out maybe twice a month to start up my car that is waiting patiently under its car cover. I have been allowing her to run for about 15-20minutes at a fast idle before shutting it down. The outside temp has been around 29f when I did this and someone told me that I am eating away the exhaust pipe cause I don't let it run long enough (though the temp gauge reads 'at temp' for about half the run time). and that moisture builds and ends up sitting in the exhaust pipes allowing them to rust. Do you feel 20minutes is long enough to let the engine idle? Or am I better off just leaving things sit until spring?