Time saved? Don't you have to buy the materials? Get rid of the waste? Get the car set up? Bring out and put away your tools? Clean up? You think you can do it than a Honda mechanic who does this for a living on thousands of cars?
Yes, one does need to purchase the materials. I typically pickup my motor oil when I happen to be at Walmart and I'll pickup the two quarts of Honda Dual Pump Fluid II (differential fluid) when I pass a Honda dealer in my travels. One can also purchase these materials via a variety of online sources. I dump my oil waste into a 5 gallon gas container and when the container is full, I stop by one of the auto service stations and dump out my container. Some towns have a place where one can dump their oil for recycling. Along with oil I can also recycle antifreeze, certain chemicals, batteries, mercury containing devices, etc.
Already have the tools to complete the job. To change your motor oil, you don't even need to jack the car up. Have a tool chest, so retrieving and putting away the tools doesn't take much time.
Cleaning up does take a bit of time, hence when I do these types of jobs I try to work on more then one vehicle at a time.
I'm an avid motorcyclist and tires on a motorcycle don't last very long. I would remove my wheel, purchase a tire from an Internet tire seller and take the wheel and tire to a shop and have them remove the old tire, install the new tire and balance it. Over the years I noticed the price creeping up for what I thought was a simple job. Keep in mind most shops have their junior mechanic work on tires. Well, I got tired of wasting my time dropping off the wheel, and either waiting or coming back to pick it up. I solved that problem. I purchased a manual tire machine. Now I change my tires myself on my schedule. Rims are never scratched. Not sure if the machine has paid for itself yet, but the quality of the job is better. I also thoroughly clean the rim before installing a new tire. no shop is doing that for you. And the job is done on my schedule, maybe at night, on the weekend, etc.
Plus, my friends will stop by with a few beers while we work on their motorcycle tires.
For me, I like the personal satisfaction of doing a job.....I also like the money savings!