On Monday, February 4, 2019 at 4:45:38 PM UTC-5, Tom Del Rosso wrote:
If you turn over an engine periodically to keep it charged, how long do
you run it to make up for the charge lost in starting?

In this case it's my neighbor's 87 Buick Regal while he's in the
hospital.


--

God Help Us! This was given in Drivers'Ed. I must be VERY old.

The rules of thumb are as follows. All times at ~1,000 rpm.

a) For a pre-catalyst car, a minimum of 15 minutes. This will bring every part of the system above the temperatures necessary to boil water out of the oil and the exhaust. This will also re-coat the cylinders with oil - which tends to be rinsed off by the very rich mixture on starting, especially when the outside temperatures are below freezing.

b) Post-Catalyst, carburetor: About the same, maybe only 10 - 12 minutes, as the catalyst will do a fine job of heating the exhaust. A V8 or other large-displacement engine will take longer.

c) Fuel-injected, 7 - 12 minutes. This directly related to engine displacement. Big = more time.

The physics of removing moisture from the oil becomes the driver (pun intended). The system must reach full operating temperature and stay there for a couple of minutes. Pretty much when moisture (steam) stops coming out of the tailpipe - and then a few minutes.

If you open the oil-fill cap and find a milky foam, you haven't been doing it long enough.