Kim C - ???

According to my old maintenance manuals, in the "olden days" the normal recommendation was to change oil every 500 miles, if you were operating in "city traffic." Pre 1950s, they might say it was "permissible" to go 3,000 if you operated only on "long trips."

The automakers finally realized that everyone was saying "3 blocks to the supermarket" is pretty long, so they quit pressing the difference, and just settled on "every 1,000" during the 60s and 70s.

Compare the 3,000 mile interval now with the 1,000 mile interval in the 60s or 500-600 miles in the 50s and before. That is progress.

Note: Even though 10-W40 is the only grade sold a lot of places, no auto manufacturer in the US has ever listed it as an "approved" grade. Oil company marketing clout prevents them from saying "don't use it," but in personal communications with GM Research, I've been told - in private - "don't use it." Check your own book.

John