1. Weathertech all-weather floor mats
2. Weathertech all-weather trunk liner
3. DropStop
4. Neoprene seat covers
5. Grocery bag hung on the passenger's side of the gearshift for trash (assuming a center-console automatic shifter; just chuck the whole bag when it gets full)
6. Wash as needed (soft towel & water; at least monthly)
7. Wax as needed (DA Polisher Pro: day 1, synthetic; day 2, carnuaba; day 3, second coat of carnuaba; would do monthly if I had a heated garage for the winter)
8. Shopvac for vacuuming (weekly)
9. Small 12V tire pump in emergency kit for topping off tires (as needed)
10. Gas fillups (bi-weekly top-offs)
11. Couple bottles of windshield washer fluid (top off monthly)
12. Spare set of wiper blades in trunk (replace as needed & reorder off Amazon from my phone when they get used)
13. Swiffer dusters (at least monthly, or as needed, for the dashboard & other plastic parts)
It's expensive up front, but it's like putting an Otterbox on your car. The floor & trunk mats rinse off really easily. The DropStop prevents crap from sliding down under the seats. The neoprene seat covers also hose off & are waterproof in case you (or your kids) spill a drink or something. Never have to worry about getting the interior of your car detailed because everything is protected (also great for resale value!). The grocery bag is a simple hack, just a convenient place to chuck garbage & then just throw it away & replace as needed.
I prefer just washing with my cars with water instead of soap, so just a soft towel & a continuous stream of water, plus some misc. tools like a toothbrush for tricky spots like rims. Claybar etc. as needed. The waxing job is actually pretty quick too, even if you do it manually (3 days of waxing, 24 hours between coats, but just let it dry & then rub it off). The MT300 polisher really speeds things up, although it's pretty pricey ($205 on Amazon right now).
Maintenance pretty much just boils down to: chuck the trash & fill up the tires as needed, spend 2 minutes vacuuming it out once a week, wash & wax as needed, hose off the mats, trunk liner, and seat covers as needed (maybe once or twice a year, like at the end of winter or if you get them really muddy), and top off the windshield wiper fluid & Swiffer out the inside on the first of every month.
For gas, I top mine off Mon/Wed before work & top off my wife's car Tues/Thurs before work. This usually results in never having to make a pitstop for gas (aside from roadtrips) & we pretty much never go below half a tank (in case of emergency). Used to run it to 1/4 tank (or sometimes til the fuel light came on), but now I just have a reminder alarm on my phone 15 minutes before commuting to work every morning, so I go do a quick 2-minute fillup four times a week & never have to worry about it
It may be weird, but I like to put preventative maintenance items as recurring events on my personal calendar (I have a Gmail calendar called "Car Maintenance"). I am a fan of personal process automation because it keeps the status quo without you having to think about it...gas is always filled up, wiper fluid is always filled up, washing & waxing happens on a regular basis, etc. Like the windshield wiper fluid, my alarm goes off on the first of every month, I run out & refill the tank to top it off before work, and I never have to worry about running out, ever. It's a small thing, but it's just another thing I don't have to worry about it because I have reminders for these little 2-minute projects so I don't let things slide. Over-think your system up-front & then just coast on cruise-control with minimal effort after that :thumbsup: