On Wed, 31 Aug 2011 16:14:54 -0700, SMS
wrote:

On 8/31/2011 3:38 PM, Tony Miklos wrote:
On 8/31/2011 6:24 PM, SMS wrote:
On 8/31/2011 2:47 PM, Tony Miklos wrote:
On 8/30/2011 9:17 PM, SMS wrote:
If changing oil at 3000 miles is
cheap insurance, than changing it at 2000 miles, or 1000 miles, is even
more cheap insurance, though actually changing oil too often is not
good
for the engine either.


Please tell me how changing the oil too often is not good for the
engine.

Two reasons actually.

First is that new oil has chemicals that accelerate the deterioration of
the catalytic converter.

"That oil change? Turns out every 5,000 miles is often enough. New oil
has chemicals that eat away the catalytic converter, says Donny Seyfer,
a Colorado-based certified master technician, and changing oil too often
can damage that pricey part."

So when did the catalytic converter become an engine part?

Yes, you're right. I should have distinguished between exhaust system
components and actual moving engine parts. BTW, certain oils cause more
problems for catalytic converters than others.


And the CURRENTLY RECOMMENDED AND SUPPLIED oils do NOT damage the cat.
They have almost totally removed the zinc and phosphorous extreme
pressure additives from all the oils from 10W40 down
Second is that as the oil ages it becomes less volatile.

"Oil volatility is at its greatest in the first 3000km after an oil
change. After that the volatility reduces and the oil stabilises.

Volatility is particularly bad for a DI engine because all of the lost
fractions exit via the PCV system. Much of it goes out through the
rocker cover vent, into the intake, through the turbo compressor and
intercooler, then puddles in the bottom of the inlet manifold where it
combines with the stuff coming through the PCV valve to coat the inlet
valves and combustion chambers in gunk."

Bottom line, do your engine a favor and don't overdo it. 5000 mile oil
changes are more than enough.

Now you may have had some real info above, I don't know, but you ruin it
all by telling me how often to change my oil without knowing what kind
of vehicle I drive, or under what conditions I drive it in.

You're right. You may actually have a vehicle that requires 3000 mile
oil changes. Sorry.