Oil Life

Bob Shuman wrote:
> I thought you were of the opinion not to believe the marketing info from oil
> manufacturers since they benefited from shorter oil change intervals?

If the oil company says six months, then you can probably go for a year.
But a lot depends on how the low mileage is accumulated. Is it a few
long trips, or daily trips of one or two miles?

"Bob Shuman" > typed until their fingers
bled, and came up with:

I mean, if Mobil One sitting in a sealed plastic
> quart bottle stays good indefinitely until used, then why does it
> magically break down once placed into a crankcase?

because sitting in the bottle, it doesn't get heated, swirled around,
contaminated with water, fuel, blow-by, etc.

--
Visit the Saturn Performance Club - http://www.saturnperformanceclub.com

Bob Shuman wrote:
> I thought you were of the opinion not to believe the marketing info from oil
> manufacturers since they benefited from shorter oil change intervals? I was
> more interested in understanding what happens to the oil over time that
> makes it require changing and if this varied based on usage/no usage. I
> mean, if Mobil One sitting in a sealed plastic quart bottle stays good
> indefinitely until used, then why does it magically break down once placed
> into a crankcase? I do understand that the oil gets contaminated through
> use and also can accumulate water from condensation, etc. but won't this get
> evaporated back out when the engine gets hot?

The water does evaporate, except if the vehicle is used only for short
trips where it doesn't stay hot enough, long enough. The oil additives
neutralize the contamination, up to a point. And it's at how many miles
that point occurs, that is the subject of the debate. The oil certainly
doesn't lose its ability to lubricate at 5000, or even 10,000 miles, but
at some point it becomes saturated with suspended contaminants.

> The reason for my question is that I have a summer pleasure vehicle that I
> put away each winter and generally only drive for 2-3K miles per year. I
> use Mobil One in that vehicle, but only change the oil every Spring so it
> gets done once a year. I have not had any issues... I also have another
> vehicle that gets driven about 5-6K miles per year. This one gets changes
> at 3K miles so gets changed about 2x per year. I also have seen no issues
> with this vehicle either. Just wondering what others do and the
> logic/science behind the rationale.

The logic behind a time period as opposed to a mileage figure, is
because the automakers are assuming the worst case, that the vehicle is
used for many very short trips.

Of course any issues you might see are in the engine life, which could
be reduced, but you wouldn't really know it because it's more like you'd
get 150K miles rather than 250K miles.