Hello, I recently acquired a 1994 Pontiac Grand Prix SE 3.1L, with 109,000 original miles on it. It's been sitting for a little over a year. We have taken it to the mechanic and replaced a few belts and parts. We've put about 1000 miles on it so far, and is on its second oil change, soon to do a third. We have been using 5W-30, conventional Pennzoil. My question is should I continue to use conventional for a couple more months, move to a semi-synthetic, or dump some High Mileage oil in it, because of age. The car has not used any oil, nor has any leaks. Any feedback would be appreciated.