This calculator is designed to supply the area of any potential collection surface of any length and width in square feet and/or square inches, based on the length and width values entered in feet and inches, and the potential and estimated actual rainwater recovery in gallons.
It depends! Read the owner's manual for the brand of car you own or want to drive as each auto maker determines when to change the oil. Generally, I've read and experienced that full synthetic oil can last up to 5K-7500 miles, but... it also depends on other factors such as your driving style and where you live. VW has listed in its newer cars, like the 2015 VW Golf, that oil changes can be done in 10k miles!
If you have been doing short trips in town you will need shorter oil change intervals than if you are driving on the freeway a lot. It also depends on the type of oil. Synthetic oil will go a lot longer than mineral oil without sludging. What you don't say is 1000 miles past what - how many miles it has actually been. If you are up to 4000 miles now it is no big deal. If you are up to 11000 miles now (some cars, especially in Europe, are going to 10K mile intervals) that is a bit much. My Prius sedan has 7500 mile intervals, 5000 in severe conditions.