> My Honda's manual called for 7,500 mile changes, and that car used
dino
> oil.  Changing every 3,000 miles just wastes oil, unless your
owner's
> manual actually calls for it.  Few do, if you take the time to read
them.

regrettably, if you read the small print in that section about oil
changes, you may find that it states "under severe conditions, change
the oil more often". some even state the 3,000 miles limit "under
severe conditions". and elsewhere in the manual, they'll mention that
city driving, under stop and go traffic, IS "severe conditions". :(
Ford does that. so did the vw's that had 7500 miles as their
'recommended service interval".

basically, they were playing the lawyer game, though. the trick is to
change the oil "whenever it needs to be changed". :) and that depends
a lot on the driver and their ability to factor in the temperatures,
driving conditions, etc., etc., etc.

the best rule of thumb i've ever heard was:

change the oli every two months in winter or 2000 miles, whichever
comes first.
change the oil every three months in summer or 3000 miles, whichever
comes first.

i used to have my oil analyzed, until it became too expensive, and a
dino oil BEGINS to change viscosity at about 1800-2000 miles. that is,
a straight 30w oil will begin to become thicker as the more volatile
parts evaporate or get used up. at 3000 miles, a 30w oil was now a 46w
oil. and yes, i ran some unused fresh new oil through their system,
just to test 'em. ;)

when i changed to 20w50 oil, all it came back was a 50w oil. at 3000
miles. so i dropped my oil change level down to 2500 in summer and
2000 in winter. or the two months in winter and three months in
summer.

works for me. :)

joel