Im looking to find a replacement for my 99 Park Ave that has 200k on it. I see a lot of Ultras for sale...How are these for reliability compared o the non supercharged models ?? Are there UIM or LIM issues with these ?? Maintenance ???

I find the supercharged version is less trouble. No UIM to crack and leak. They have the same LIM gasket problems, but that'* easy enough to fix. Listen to the SC for any odd knocking sounds. If you hear anything complain and get the price knocked down. Then fix it. I can get you a new supercharger for $100 and I'll even throw in a new gasket. It'* a hour and a half job if you have basic knowledge. And the only tools you need is a 10mm socket and a inch pound torque wrench. Oh, and a fuel line removal tool, and those are cheep at places like autozone.

any maintenance on the SC ? Like lube ??? Hows the fuel mileage?

You can change the snout oil, it'* like 8oz, but that'* really about it. The mileage will be about the same as long as you use premium. I was getting about 28 on mine provided my evil right foot stayed home.

oh man you have to run preminum....skip that then

Yep, you don't want to be running 87 in a boosted engine. You do get better mileage with 93 when compared to 87. And that difference will more then off set the extra $0.20 a gallon.

A sc coupler is ~$40 to swap out including the oil. If the charger is making noise, that'* the typical fix.

But yeah... Super Unleaded.