On Friday, August 28, 2015 at 3:10:43 PM UTC-4, wrote:
On Friday, August 28, 2015 at 11:25:50 AM UTC-7, trader_4 wrote:
On Friday, August 28, 2015 at 1:08:02 PM UTC-4, Oren wrote:
On Fri, 28 Aug 2015 12:57:14 -0400, "Percival P. Cassidy"
wrote:

-old (140K miles) Chrysler and doing oil changes at about
4000 miles. The owner's manual doesn't mention synthetic lubricants but
specifies a time period after which oil should be changed -- "x miles
or x months, whichever comes first."

I've never understood the "x months" thing. If the car is not being
driven, except on Sunday, why change the oil until the "x mileage" is
reached?

I think part of the assumption there is that if you're not hitting the
miles limit, then you're probably driving it for shorter distances,
where the car doesn't have time to warm up properly to drive off moisture,
so the oil winds up compromised from that. Which is why the new method
where the car computer keeps track of the actual usage conditions is
better than a fixed schedule. But I've also never seen data that shows
oil is indeed compromised in a year if the car is just driven lightly.
You could probably go way beyond that and it would still be fine. I'd
be more worried about the miles than the time.

my 2014 Avalon also uses synthetic

10,000 is longer than we used to change oil

how about 7,500 miles as a compromise?
especially since you are changing it yourself, and saving a few bucks

[it gets pricey, having someone else do a synthetic oil change]

marc

When the oil change interval was typically 5,000 miles, we also didn't
use synthetic oil which is a very different product. In this case
the vehicle manufacturer says 10K and that would be good enough for me.