I've changed the oil the day before yesterday (from 5k mi
old Castrol Syntec to new oil of the same kind).
The car is a '97 Zetec with 155k, I've been using synth
or blend since 110k, 5W30 always, changing between 3k-5k
depending on traffic pattern.
I'm not consistent on the kind of oil,I pick it depending
on my mood/wallet at the moment (synth or blend). Been using
Castrol frequently (not exclusively) because it's cheap.
I use Motorcraft filters all the time, FL-200 or FL-300
(Walmart gives one, dealer gives another, I guess they're
the same. Both fits.)
At this oil change what came out looked as thick and
black as I expected from an 5k / 3month old oil, nothing
particular. After filling up with the new oil, the sound of
the engine changed very much, I'd say for the better: much
smoother idle, nicer sound.
It changed so much that even a friend who occasionaly rides
in the car noticed it.
I've never had anything like this before, and I'm quite
puzzled. The engine is still in a good shape, doesn't burn
or leak oil.
Any comments ? What could cause this ?
Thanks,
Tiv
