Dear Car Talk:

The under-engine cover (the tough plastic panel attached to the underside of the car behind the front bumper under the engine) on my 2005 Acura TSX recently started dragging on the ground. After sizing up the situation by the side of the road, I drove a few miles home, got under the car and gently removed (hacksawed off) the remains. The internet seems convinced that these covers serve no great purpose, and that you can drive indefinitely without one, so long as you don't mind increased road noise and reduced fuel economy. This seems wrong to me -- auto manufacturers are infamously frugal, and they would not add a part for no reason. How quickly does a missing under-engine cover need to be replaced? Thanks.

-- Alex

Are they open today?

Actually, it's hardly an emergency, Alex. But I would recommend that you replace it. It not only contributes to better gas mileage, but it also provides some protection from road debris. We've seen instances where someone drives over a branch and the branch rips off one of their belts. That costs them $200 for the repair, plus the cost of the tow. And by the time they're back on the road, they've missed their brother's rehearsal dinner.

Or, if you drive over a sharp object, it's possible it will puncture that piece of hard plastic, rather than puncturing your oil pan. That'll cost you even more, and possibly an engine if you keep driving.

And most of these engine guards don't cost an arm and a leg -- maybe just one arm, up to the elbow. I'm guessing the replacement part will cost you about $100.

We often try to reattach them when customers drive in with them dragging on the pavement. There are various places we can add new sheet-metal screws if the old ones are stripped or have been torn out.

But if we can't save the patient, we'll just tear off the thing, like you did. Then we'll recommend that the customer come back and have a new one installed, but we never see them again. Until they drive over a branch.