frequency of oil changes

[dardal@xxxxxxxxxxxxxxx]

This has been discussed before.  The reason why the FSM says 4000 or 3 months is
in order to proctect the car from short trips.  Remember, when the cars were
new, oweners were using them as daily drivers, not as garage residing machines.
 If the driver drove 1 mile to the grocery store, then two miles to work, and
back one mile home every day, the car may get very little mileage, but lots of
gasoline and water in the oil.  The situation would be even worst in cold
weather.  If you don't drive the car short trips, and you don't just start it
every now and then without driving it, then its safe to leave the oil in there
for a long time.  If you have the bad habit of just starting the car without
driving it, while the car is stored, may be you should change the oil before
you reach the 4,000 miles.  Finally, if you use synthetic and avoid short
trips, you may be able to keep the oil in there for much longer periods.
D^2

Quoting Mark McDonald <tomswift@xxxxxxxxxxxxx>:

> I changed the oil in my '68 yesterday and got to wondering.  In the 
> FSM, it says to change the oil every 3 months or 4000 miles, whichever 
> comes first.  I haven't put on 4000 miles on this car since I bought 
> it, so I haven't changed the oil in 3 years, figuring, well, mileage is 
> the key thing.  But now I'm wondering if time itself is a factor.  Will 
> old oil go "bad" in the crankcase?  Should you change your oil every 3 
> months REGARDLESS of how much you drive?
> 
> Thanks, Mark
> 
> 
>