An L48, if it uses the PF25 or equiv., takes 4.5qts total. If you use the, larger, PF35/PF1218 sytle, it takes 5qts, total.
The two best oil filters on the market right now are the Mobil 1 and the K&N Performance Gold. Unfortunately, neither are inexpensive.
The idea that you need to change oil in an engine that sees normal duty cycles every 3000 miles is a myth propagated by the "quick lube" oil change industry. It's a waste of money, effort and can even be harmful to the environment, depending on how your manage your drain oil.
The oil change interval on an L48 is 7500 miles. There is no reason to change it sooner than that, especially with today's modern engine oils. Where there can be a long-term durability benefit is changing the filter at half that. That is, use the long type filter (PF35/PF1218) and change it every 3750 miles.
The only time oil change interval of a pre 97 Corvette needs to be less than that is if the engine sees a frequent starts-without-warm-up (ie: "short trips") or frequent operation in a dusty environment. If the engine is used in those duty-cycles, the oil and filter change interval is 3000 miles.
Many people scoff at the idea, but it was raised here briefly in another post to this thread so, here goes: if you use a good quality synthetic oil, such as Red Line or Mobil 1 10W30, you can use an extended drain interval. I run my Corvettes 10,000 miles or one year and I run my daily drivers 16,000 miles or two years using Red Line 10W30. I've used this interval sched. for nearly a decade. I backup my oil changes with spectorgraphic oil analysis every time and, provided you use a good synthetic oil and change the filter every 3000-4000 miles, the results are excellent.
