Hi there. I just bought a 1999 Cadilliac DeVille. 32V Northstar. I paid $6200.00 with warranty. The car has 81,000 miles on it. It drives and runs like a dream. Everything seems to work. I got in touch with the machinc who worked on the car for the original owners. (Oil Change Sticker, lol). He said the car was in great shape. He just put on Valve Cover Gaskets due to oil leak. Is there anything that I should be doing to car? I am taking today for an oil change. I have been doing some research and I see that Northstar engine is good but needs TLC. I also saw that the coolent GM uses is not good? Should I go get it flushed? Any type of good coolent? I want to keep this care for long time. It is in really mint condition. Garuage kept! Thanks everyone for any advice that you can give! ;)

Dex Cool ONLY
change every 4 years recommended by GM
change every 2-3 years recommended by us long time owners
be sure to add two coolant pellets (bars leak) in the upper rad hose NOT THE SURGE TANK

be sure to WOT her every so often to reduce oil consumption and carbon build up (the car was designed for it)

for any issues with lamps or problem messages pull your codes via the on board diagnostics before posting here as we cant help you anymore then your car can and it has codes to help us tell you whats wrong (on a 99 Deville you do this by holding the OFF button and the red temp up button until your whole dash lights up like a Christmas tree)

that said welcome to the group enjoy your stay

There's absolutely nothing wrong with DEXCOOL long life coolant. Change it, as recommended here and elsewhere, every 4 years, and, for your (new) car, add the GM recommended supplement tablets. Hundreds of posts in here. Catch the mechanic again and find out when (if) he changed the coolant. It's not quite a real "flush" for a N* because, for the DIY mechanic about 4 - 6 quarts of coolant remains in the engine because there are no block drain fittings, and if you backflush with plain water you play hell getting back to a 50/50 or slightly higher coolant percentage mix.

Mae sure you read the owner's manual for recommended oils and don't try to second-guess the GM engineers. If you're going to change oil/filter too often (3 -4,000 miles) a good conventional dino oil is perfectly fine.

Hi again! Thank you for all the information. I had the car serviced. They changed the oil with 10W30 High Mile Pennzoil, and flushed the coolant. But they put in a compatible coolant that is compatible for all coolant colors. They said almost every GM car they they have service has had sludgy build up from th Dex cool. So they use multi-compatible fluid (yellow not green), its silicate free? The car is not running at $196'F. They said this car is so clean it looks brand new! The valve train looks shinny still! The only things is, I noticed since i got the oil change, it does have a little tappy tap sound, not loud but only a bit after its been off for a while. Almost like the Chevy 3.1-3.4 V6 motors. It runs phenomenal though! transmission I am going to service. I am a teacher at Tech High school in NJ. The automotive instructor use to work for a Cadillac dealership. He said he would do it in shop. I forgot to ask what kind of fluid I should get? Any other things I should be aware of? I did notice a little creak noise coming from the front passenger side when i go over bumps. Thank you all for everything! This is a great site!

The sludgy build-up is not from the Dex but from the RECOMENDED Barr's Leak tablets and is normal. Ckeck the sticker on the radiator cowl that recommends you use them unless your 99 is different from mine. Not sure about the magic coolant - I have only used Dex in my car so far.