Ran very low on oil did I do damage?

I just did the same in my 97 expo.  Had about 1qt when doing oil change.  Oil light was intermittently coming on. Going to cross my fingers.

The only way to check is to add oil and feel the car if it runs the same.

you can do a compression test on each cylinder.

why low oil? leak? fix it, or say goodbye to the engine. 5 quarts its a lot!!

That engine holds 6 plus quarts. If you were truly 5 quarts low, you have oil going somewhere. If you have no knock, good oil pressure, you may be able to drive it quite a while. However, if you got it hot, you can experience bearing failure at some time in the near future. Without tearing it down, you wont know. Drive it and keep an eye on the oil level.

You're lucky the motor isn't seized up. 5 quarts low is not only not enough in the motor to keep the oil pump from cavitating, the little oil that was remaining had to be dirty and black which means the oil wasn't lubricating enough too. Most people that end up with little or no oil in their motor don't change the oil every 3,000 miles so there's a very good chance your bearings were not in the best condition already from past neglect.

Caught it in time. Keep your eye on it from here on. But, oil also helps remove heat from internal engine parts and will burn if not enough of it is available.

As long as your oil light works and was not coming on (or even only a flash now and then) you had enough oil to prevent catastrophe, but during that time the cylinder walls will wear, putting years on your car. It was running hot and with minimal lubrication. It should be fine okay, but if it began to burn oil or misbehave in other ways I would not be surprised.

So now you should have all new oil and filter, right? You have to make some penance or the automotive gods will come down on you.

When was the oil last checked before discovering it was low? How many miles have you done since then?

Running that low will not have done the engine any good.

As other post said, check all your warning lights are working. It is odd you did not have a warning light come on. Are you 100% sure you have not over filled the oil?

I am guessing if you were doing local driving, then oil was circulating and not getting overheated, then maybe just some additional wear. But really there is no way to know how much additional wear was caused.

Why so low, is it burning or leaking oil?

The first thing you need to do in say a few days is get an oil and filter change. I know you just put fresh oil in it, but that 1-2 quarts of old oil has to be totally thinned out and dirty so all the oil is contaminated. Just my opinion and since you ran it low, keep up with oil changes going forward.

Your check oil light should have come on on the dash board. You did not mention that so I am assuming it did not come on. You also say the truck ran fine. Based on that I would say it was not low on oil but rather you read the dip stick wrong. How do you know it was five quarts low? I hope you did not dump in five quarts.

hard to say if any real damage was done