What kind of oil does a 1999 mercury grand marquis take?

Answer 1

5w-30

According to the manual 5W-20 is the recommended oil during the lifetime of the vehicle. This applies to both Grand Marquis, and Crown Vic models for the year and beyond.

Suggest to use a synthetic blended version 50/50 synthetic blend after 75000 miles, and use the 5w-20 version of this as well.

Police departments in several northern counties all over the U.S.A. also use the 5W-20 weight in the cold climate as standard too, and all cars in the north or south of the U.S. after the first 30,000 miles of driving require 5W-20, standard oil, or synthetic, and or synthetic blended oil for police.

5W-30 should strictly be used in desert climates. The newer oil channels of Fords Modular engine are much thinner in diameter. And require thinner oil. The use of 5w-30 in normal climates leads to blockage in the channels, and premature engine knock. Most notable during a cold start at first and the 2 second knock sound. And along with a smoky tail pipe for the first morning crank.