My owner's manual (1995 YJ) says to "Select oil viscosity according to the
lowest air temperature expected before the next oil change using the engine
oil viscosity chart". According to the chart, 5W30 is good up to a "lowest
air temperature expected" of 60º, and 10W30 is good down to 0º! There is
considerable overlap there. According to this information, I could probably
get away with either 5W30 or 10W30 year round, living where I live.

It's not just easier starts. An oil that is too heavy can cause increased
wear during cold starts, because it doesn't get to the bearings fast enough.
Gene Berg said that "the heavier the oil, the less it lubricates"
http://www.geneberg.com/article.php?ArticleID=237 third paragraph. Ignore
the part about clamping a cow magnet to the outside of your oil pickup tube.
;^)

Like you, I would probably have chosen 10W30 for an oil change in August,
but this little misunderstanding won't hurt anything.

Earle

"DougW" > wrote in message
news:P1KFg.1554$JR5.977@dukeread11...
> This is what I get for dropping my Jeep off at a Dodge dealership for
> a quick/cheap oil change. Oh well, worst off I run for a while,
> flush, and refill. Only $19 for a full oil flush isn't bad.
>
> By the receipt it looks like they put 5 quarts of 5W30 in.
> ..er..
> Should be 6 quarts of 10W30.
>
> I gotta start paying more attention....
>
> Oil looks nice and clean but 5W is more for < freezing expected
> in the next interval. It's close to fall, but not that close to
> winter. On the other hand the oil is only 10 cold with a viscosity
> of 30 at operating temperature. i.e. more for easier starts in cold
> weather.
>
> I'll top off the oil with some 10W30 synthetic so that's not a biggie.
>
> Still though, I've got a few more thousand miles of travel in 90+ weather.
> From what I understand there really isn't an issue since the weight is
still
> 30 and the engine operates at the same temperature anyway.
>
> Thoughts?
>
> --
> DougW
>
>