if I get a 3.6 will I loose a lot where I can not see both cars?
Use the
IPVM Camera Calculator V3 tool for this. It'll let you put just about any model camera on a Google Maps image of your house which shows you the field of view as well as the PPF value. The recommend PPF value to ID someone you don't know is 100+.
Using that calculator with the new 4MP 5442 turret model (distance set to 18FT):
2.8mm: the view would be 54.0 ft wide, PPF would be 49.4
3.6mm: the view would be 35.4 ft wide, PPF would be 76.0
6.0mm: the view would be 19.1 ft wide, PPF would be 140.4
The calculator tool will bring up a Google Maps image of your house if you type in your address, let you position the camera, and then show you how wide the video of view will be at any distance. Definitely takes a lot of the guess work out.
Here's how a 3.6mm 5442's field-of-view would look on my driveway at 18ft.