Do Tires Have To Match on a Front Wheel Drive Car

Can I use a different weight oil in my Ford Flex? Why does my 2002 Ram engine stay cold? Thermostat? Should I fix my battery drain or use a maintainer? My 2017 GMC Sierra won't start. 1999 Mercury Sable won't start after filling with gas. Do my tires have to match on my car? I can't get my dipstick into my Ram engine. The Eclipse after show