Since you got the car with 42,000 miles on the clock there's no way of knowing how it was broken in or how it was used prior to your owning it, unless you can contact the previous owner [s]. Even then you may not get a completely honest answer. My guess would be that something happened prior to your buying it that accounts for at least part of the oil consumption issue. You stated that you hammer it pretty hard and do so frequently so that probably has some bearing on it too. IMO a quart of oil in 1,000 miles is significant for a modern low mileage car assuming it had a reasonably decent break in and wasn't absolutely beat to death. I bought my '14 GT new and broke it in hard, but not to the point of abuse. I use Mobil 1 5w30 full syn and it only used a small amount of oil in the first 1,000 miles and since then it dosen't use any measurable amount between 4,500 mile oil changes. I am at 25,000 miles now. As for what oil and weight to use, well talking about oil is a little like discussing politics or religion, there's no shortage of opinions. I am not an engineer of a petro-chemist, just a guy with a reasonably open mind and long experience with racing and high performance cars. To the best of my knowledge when you look at the numbers of multi weigh oils the first number indicates the cold flow rating and the second is it's protection ability. In other words a 5w30 oil should flow when cold like a 5 weight oil and give protection equal to a 30 weight. The other numbers have to do with how it meets the auto manufacture's specifications and how it's rated by the petroleum industry. As others have previously noted the climate the car is used in and how it's used have a lot to do with what oil to use. If it were my car I would do both a leak down test and a compression test if you haven't already done so. Also as has been previously suggested carefully check the engines crankcase ventilation system. Good luck and try to let us know what you find.