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TW wrote:[color=blue]
> I have a new '06 Rav4 nearing an oil change. I've used Synthetic in my
> other 2 cars since they were new, but Toyota recommends one NOT use
> Synthetic oil.
>
> Is it because (a) they want to support the local Toyota dealership garages
> and simply recommend one NOT use it so we take our vehicle to their garage
> and use their crappy oil OR (b) is there a real mechanical reason they
> recommend against using synthetic oil? The mechanics at the garage have a
> gag order and won't discuss it.
>
> Thanks!
> TW
>
>
>[/color]
Lots of misinformation about synthetic oil in the postings above and
the link to the motorcycle oil info.

The ONLY way to tell when to change oil is by having a testing lab
analyze the oil. This costs about $20. It obviously isn't worth
the money to do this every time, but can be done a few times to show
a trend. Here is a report of a Chev engine with Mobil 1 oil that
was tested every 1000 miles, 4 ounces of added every 1000 miles to
make up for the oil removed for the tests, the filter changed at
12,000 and new oil added to fill the new filter, and the MObil 1 oil
finally dumped at 18,000 miles.
[url]http://neptune.spacebears.com/cars/stories/mobil1.html[/url]

Oil rarely has to be changed because of contamination.
[url]http://theoildrop.server101.com/forums/postlist.php?Cat=0&Board=UBB3[/url]

More often it needs to be changed because of oxidation or because
the additives have become depleted. The better oils use higher cost
additives with longer lives. Sulfur is not a concern...both
gasoline and diesel fuel have sulfur levels so low that now the
sulfur in oil, the "thio" in certain additive components, is being
lowered.


Ken