I bought a 1997 Pontiac Bonneville for next to nothing. It had a failed upper intake manifold like they all eventually do. This led to coolant in the oil (it looked like the coolant was mostly water - not much "coolant" at all), failed headgaskets, and one slightly cracked head. I've just about got it back together properly, but I know that a few instances of lower end problems have occured after this repair. I actually already have a '98 Bonneville, for which I did the UIM repair. It didn't cause any lower end problems on that one, although it did get a little coolant in there at the end. I just did an oil change, and went on about my way. I don't know how long the 1997 went in this state, and I realize I'm rolling the dice. Is there anything additional I can do with the oil (specific oil, additives) that can help me put the odds in my favor?