Either a 2.3/2.5 4cylinder or a 3.0 V6
The PVC valve for a 1991 Skylark should be located on the top of the valve cover. It is a plug in type, twist and pull to remove.
Type "1991 Buick photos" into your search engine. If you are interested in a particular Buick Model then add that model such as "1991 Buick LeSabre photo".
Type "1991 Buick photos" into your search engine. If you are interested in a particular Buick Model then add that model such as "1991 Buick LeSabre photo".
R134a
Gool ol' Dexron.
5w30 Your brand. Most are all the same
Depends on what type of 1991 Buick you're referring to...
Originally R-12 - should be converted to R134A
Century, Regal, Grand National, LeSabre, Electra, Skylark, Skyhawk
If it's an automatic, most likely a Turbo 350.
Dexron III, but check with any auto store first.
Well it depends on the type of engine you have, but that only has to do with the thermostat's location. The Haynes GM manual #38025 has instructions on how to change the thermostat in section 3-3. Amazon has copies of it dirt cheap.