12 volt battery of choice?

The 12v battery of choice is the original battery from Toyota. Most manufacturers have priced their batteries around $200- $250 now. So for that price, you should just get the original.

As for the gas tank, it seems normal for the cars to take less gas in winter months. When the temperature warms, the bladder in the tank will be able to take more gas. Not 12v related

 

This is normal as you're not putting in as much gas during fill ups. MPG probably still averages out the same, just you can't put as much into the tank right now.

Is Atlanta colder than previous years? I'm having the same problem in CA and it's not really cold. I normally can get 350-380 per tank, now I need to fill up around 300

 

The sensor in the tank is probably going bad. Our Gen2 has been doing this for about six months. We go by the trip odometer now. You can try calibrating the inclination on the sensor which I have not done yet.

SM-G960U ?

 

I’m going to try the Batteries+ AGM for $225. 4 year warranty.
The dealer battery is superior but there like $100 more than that here.

I’m on my second optima and not impressed and over them they really start to tank after there 3 year warranty. My second at 3 years and 4 months is showing advanced signs of degraded performance. I battery tend just so I can monitor there behavior I recommend you do the same.

nothing worse than having a dead 12 in a Prius. I check the battery voltage at least once a month at the front jump points and once every few months do the battery headlight load test which although is a very benign test is quite revealing of the battery’s reserve.

Also Good idea to check the engine oil at least once a week before starting the car. Older g2s have a habit of all of a sudden start eating oil especially if raised on Dino oil.

 

I replaced my 9 year old Optima with the NAPA battery in January 2021. The battery was in stock at my local NAPA store and after my AAA discount and a $20 rebate my cost was $166 including sales tax. The warranty is prorated after 18 months, but I'll take that risk for the $100 I saved over another Optima or the Toyota OEM battery. Other places sell the battery for our cars for around $200 plus tax, but no location had it in stock locally. I prefer local availability in case I have a warranty issue down the road.

 

I remembered after I put my iPad down that a poster mentioned a price drop on the dealer battery so I called my dealer. Pretty good deal.
$221.
7 year prorated warranty
First 2 years is $100 then proration starts parts guy not sure of exact % though probably sliding.

So that’s what I’m going with. The stock battery is the best. I bought my car new and it’s first battery lasted 7 years which to me was fantastic.
Although I did take very good care of it with full charges about every 3 months and n3ver once killed it. You deep discharge this little battery to 100% dead and hold it discharged with a light left on load across it all night it’s never the same. No car battery will enjoy that.
We see that constantly on this site.
That’s easy to prevent just look at it before going to bed every night arm the alarm so no door ajar and make sure no lights left on.

 

And you know that how, exactly ?

I don't remember the exact numbers but there are something like only 4 "factories" that make batteries sold in the US.
And two of those account for about 80% of the market, putting out batteries with something like 50 different stickers on exactly the same product.

The OEM battery is good. But there is no valid reason to think that others might not be just as good.