Hi there. A few months back, the dealer changed the oil in my 2000 S70 GLT (it was a freebee for some oversight on their part). Yesterday, I changed the oil in my car (myself) and, to my surprise, noticed that only 4 - 4-1/2 quarts of oil were drained (the oil was drained after the car was cold from sitting overnight). Prior to changing the oil, the oil level never appeared low on the dipstick. Previously, when changing the oil myself, there were always 6 - 7 quarts drained from the reservoir.

From past experience changing the oil myself (as well as from consulting the manual), I know that ~6 quarts are recommended during oil changes (and ~7 quarts if the oil cooler is drained). My exhaust appears normal and the car has never shown any indication of burning oil (and gas mileage has been normal as well). What gives? Is my car now burning oil or did the dealer (un)intentionally skimp on adding oil? How many quarts of oil should I be using? Will the number of quarts vary on whether or not synthetic or regular oil is used?

Can you tell me what an oil cooler is and how/when to drain it? Will adding ~7 quarts of oil to the reservoir without draining the oil cooler adversely effect my engine (or oil cooler)?

Thanks for your assistance.