I have a 2017 Ford F-150 3.5 Eco-Boost. One cold night this winter, I plugged in the block heater. The next day, I came down with a bad stomach bug and didn’t leave the house the next two days. It never crossed my mind that the truck was still plugged in (not something you think about when you’re making frequent visits to the bathroom).

On the third day when I moved it, I noticed a fairly large spot on the driveway. I checked all the fluid levels, and they were good. I assumed it was oil from the outside of the engine, but after about six days, the spot was gone (no rain or snow, somewhat cold temps).

I didn’t think oil would evaporate like that. The truck has been fine since this happened.

Here are my questions: Did I damage the engine by leaving the block heater plugged in for two days straight? What was the spot in the driveway: oil, radiator fluid or something else? Should I be concerned? Thanks. — Troy

No, water or coolant, and probably not.

You didn’t do any damage to the engine by leaving the block heater plugged in for two days.

All the block heater does is heat up the coolant. And it doesn’t even make the coolant hot. It just heats it up about 50 degrees or so, so it’s not freezing cold when you start the car.

If you had left the truck parked outside during the summer when it was 75 degrees out for a couple of days, that would have been no different, as far as the engine is concerned.

So, what was the fluid that came off the engine? It’s not oil. It’s not transmission fluid. It’s not differential fluid. Those petroleum-based fluids would never evaporate in a few days. If it had rained or snowed, maybe they’d get diluted a bit. But there’s a reason they call them “oil stains,” Troy. They’re really hard to get rid of.

So I’m guessing it was either a small amount of coolant, which — because it’s water soluble — could disappear over time, or it was water from some ice that melted when you warmed up the engine compartment.

And it’s entirely possible that your small puddle has nothing to do with your block heater. You could have a loose hose clamp or a dripping water pump. You came out the other day looking for trouble. Maybe something’s been leaking slowly for months and you just haven’t noticed it?

If you see the spot again, see if it’s got a greasy feel on your fingers. Coolant will feel slippery. It’ll also have a sweet aroma and taste. Don’t taste it, though, Troy, or you’ll be trotting to the bathroom again.

If it’s coolant, ask your mechanic to pressure test your cooling system. If there’s a small leak, he’ll find it that way, and you can fix it.

The dealer is right that the best way to install a trailer hitch is to remove the bumper and the bumper beam and install the hitch between the bumper beam and the frame (or unibody) of the car.

Subaru’s own trailer hitch is designed to be installed that way. But not all hitches are. There are good aftermarket hitches that just bolt into the frame on the underside of the car. Those are a lot easier and faster to install. And they might be fine for what you need. You can check the maximum capacity of any hitch and see if it covers your needs.

For instance, if you’re just putting a bike rack back there that requires 300 pounds of tongue weight when loaded, an aftermarket hitch might be fine. But if you’re towing your house or your cabin cruiser around, you’d probably want a more heavy-duty installation.

Get up-to-the-minute news sent straight to your device.