I have been using STP and Mobil 1 filters, and Mobil 5W30 oil, changing
at 10,000 mile intervals. Currently have over 136,000 miles on a 98
Dodge Stratus with the Mitsubishi 2.5L V6. Runs quiet and still gets me
over 31 MPG on the highway. If you make frequent short trips of 10
minutes or so in duration, the oil needs to be changed more frequently,
perhaps every four months, regardless if it is synthetic or
conventional. In that case it might make more sense to use conventional oil.

I was thinking of changing my oil over to the new synthetic stuff. I drive
an 03 grand caravan with a 3.3ltr engine. The first question is 1) al lot of
people are saying to go to 15w40 rather than the 5w30 that is presently
recommended when using regulare oil. Has anyone been using 15w40 synthetic
oil and had any problems with it. 2) The reason I would like to go to the
synthetic oil would be to increase the mileage between changes but I have
been doing some reading on the net and some articles suggest that the usual
oil filters you buy in Canadian Tire or Wal-mart (fram etc) only actually
filter oil for about 4000km and after that I guess the oil just passes right
through them unfiltered. Are their recommended oil filters out there that
one should use when using synthetic oil.  I don't see the point of changing
over to the better oil if the filter is not going to be the weak link?

Bill