This brings up a practical question for me. Where are we supposed to dispose of the old oil? I'm assuming not with our garbage in a used soda bottle?

Any auto parts store will dispose of oil.

DIY, as I and many others do. But save your oil receipt as proof that it has been changed, just in case.

Extended Warranty Requirement
 

When we bought a 2018 Yamaha from Villages Golf Cars, we were told that, in order to qualify for the extra 2 years of warranty coverage, they have to do all the maintenance, including the annual Lifestyle Service (it was called something else back then). It is now up to about $180 plus tax. So, if you want a 5-year warranty instead of 3, you have to let them do your oil changes..

Never have changed oil in my cart which is nearly 7 years old. In fact, it has never been in the shop or had any maintenance done on it. Oops, it is lithium electric so that explains it being maintenance free. Sorry. Disregard.

This is what I use to change the oil in my cart …. Works like a champ ! I run the cart around the block a couple of times so that the oil is warm and any contaminates are mixed with the oil .

Is that in writing? I hope you didn't just accept something the dealer said verbally as a fact. The Yamaha warranty on their website doesn't say anything about who needs to do the oil changes.

Yamaha standard warranty is 3 years, the extra 2 is offered by Villages Golf Carts - their warranty, their rules.
It’s probably self insured, because most golf carts require little warranty work (and they catch stuff early) - the carts run for a long time. For me, it’s worth $50 a year.

Im going to add...
A Great Golf car service is more than just changing the oil. There is more to it. Working on golf cars everyday here in TV, I see the DIY carts when they find they have a problem they cant fix. The crazy thing is 99 percent of the time, the issue is due to improper service, I cant count how many times I run across it. So the 50 bucks you think your saving gets taken up by the 300 dollar repair you could have avoided by having the right eyes look at it. Now I know Ill hear, " Ive done all my own service and my cart has 80k miles on it and never had a problem"... great, its just not what im seeing.
Also, as was mentioned, some services cost a lot...and some of the places that charge a high amount do everything the cart doesnt need and dont do what the cart does need. Many shops even do the work wrong...I know, hard to believe. Do you need a Air filter, fuel filter, spark plug and a belt every year? No you dont. Spark plugs and air filters last years...like 7-10 years.... I know, some one is going to say " its cheap insurance just to replace them". Really? From what? The air filters and spark plugs are never an issue.
However, many many of you are driving around in golf cars where the brakes are adjusted wrong....I know, " my cart stops fine" Doesnt mean the brakes are not adjusted correctly. See this issue with the Quiet Techs alot, as a matter of fact, I adjust those brakes correctly daily as the complaint is always, my cart doesnt stop very well. A 5 year old should be able to stop any golf car.
Every golf car has issues, its all about having the right eyes looking at it to prevent those issues, and these items are not listed in the service manual, they are issues that are just problem areas with every cart, and it depends on make, model and year as it will vary from year to year.
I like the DIY to be honest as they always find themselves in trouble at some point.
Anyway, I just thought Id point this out....Ill wait for my flogging now.

I have used Willie's Cart service for over 10 years and just had the annual service done, oil change and drive around. Both carts took a total of 20 minutes. I called and got the same office as always and the same lady scheduled my appointment which was done this past week. When I was handed the bill I almost gasp at the increase in price. I asked why it was so much ($190) and was told new owners took over and this is their rate. I could have had my car serviced at a dealership for less than just one of my carts cost ($95). Last year it was $70, This year, the 35% increase will send me searching different company.

Amazon.com

Amazon.com

The OEM Yamaha oil is on Amazon.
 

I buy the oil on Amazon. I have an older model golf car with a drain plug. It’s an easy job. It only takes one quart of oil and no filter. Cheap!

I thought golf carts burned off oil like lawnmowers do
 

I go to village golf cart store. get the oil and the small metal gasket that you replace when you drain the oil out...why are people sucking the oil out? when you take that the plug out, the oil will drain, and you will see what I mean about the gasket.....they know what you what when you ask for the little gasket... and observe which way the gasket goes back on.

On the chance this is a serious post, there are no engines work that way. All engines (lawnmower, golf cart, motorcycle, car, truck, boat) that take oil require that it be changed at a regular interval.