doggedyfight wrote:

My 150 year old house is now heated by gas. In fact, gas service has
been in the house for probably more than 100 years since there are
pipes in the walls from old gas lighting.

Looking around the basement the other day, I noticed a small stub of a
flexible 3/8" OD copper pipe peeking up from the concrete floor (it is
in the area where I believe the old boiler was from long before we
bought the house).

The inside of the pipe smelled of oil/grease and when I stuck a stiff
wire down the pipe it seemed to run at least 2 feet horizontally just below the
cement surface. Pulling back the wire, it was covered with an
oily/greasy residue.

Does this signal that there was oil heat at some time or worse, the
presence of an old underground oil tank beneath the basement?
If not, what else could this small diameter pipe have been used for?

We have no other evidence of there ever being oil heat or oil tanks in
our house.

Contrary to the others, I'd be cautious in trying to hide it too
cleverly--

I wouldn't worry about doing anything about it, but if you attempt to
cover it over and during a sale don't follow the particular rules
regarding disclosure applicable to your state you would really be
opening yourself to a liability issue were the obvious attempt to hide
it be discovered by an inspector for the purchaser, for example. I'd
put it back as it was and go on. If it were in my plans to be selling
the property sometime in the near future, I'd investigate throroughly
what is required in your state.