What to expect from battery when buying 6-7 y/o car

you don't want to know worst case, go with average case.

 

Worst case scenario for me was a highway drive in -10F weather with no warm-up and heater blasting. That was around 35 MPG at best. And long traffic jams in summer with air conditioning running can result in trip economy of 25 MPG or worse.

Average MPG for me has varied from 40-41 MPG in winter to 48-49 MPG in summer. Of course, that's in Minnesota, so you won't have so much of a winter downswing in a warmer climate.

 

I'm of the opinion that if you only read the message boards for one model of car, you'll find multiple reports of common problems and think the vehicle is a total lemon. If you read several message boards, you'll notice the pattern that most cars have some weak points that affect multiple owners. Thus, Prii have oil consumption and occasional battery issues, F150s have spark plugs that seize and need new cam phasers and timing chains regularly. Mustangs spit out their spark plugs, leak antifreeze out their intake manifolds, and have faulty manual transmissions, not to mention having the same gas tank location as a Pinto.

Of course, all these problems are minor niggles compared to having to replace rod bearings regularly in an expensive BMW: http://www.m5board.com/vbulletin/e60-m5-e61-m5-touring-discussion/298817-comprehensive-s85-rod-bearing-picture-thread.html

 

If you do a lot of city driving, the numbers will skew heavily in favor of the Prius. The Prius excels at sitting in traffic, and I typically get 60+ mpg in the summer if I stay off the highways. Of course this is in New England and driving in the morning or evening, so no heavy A/C use. When it gets below freezing, the MPG does drop significantly because the engine can't shut off as much.

Consider a downhill approach to a red light in hot weather in a Camry vs. a Prius. In the Camry, you'll have to do a lot of braking as you're both slowing down and descending a hill, then when you get to the light the engine will be running to power the A/C. In the Prius, the engine shuts off as soon as you take your foot off the gas (assuming moderate to low speed), and you'll use the regenerative brakes to capture a good portion of the energy wasted by the Camry's brakes, then use that energy to run the A/C while you're at the light. If you plan ahead you'll get maximum regeneration and minimum brake pad wear. A single stop from ~50 mph can power the A/C for minutes.

Yes, your numbers appear correct, which means you still come out ahead if you buy the used Prius and immediately go to the dealer and put a new battery in it.

 

agreed. there's no way of knowing what percentage of 2010's have problems. but i can't in good conscience, advise people to buy one without telling them what has been reported here.

otoh, there could be a lot of 2010 drivers with oil burning issues, who never check their oil.

 

I work with one of them! Never checked the oil on his 2010 until the low oil pressure light came on at about 100K miles, just short of the next scheduled service.

Somebody else here also had a 2010, never had a problem with oil burning (not sure if he ever checked either) when he traded it in on a new Prime at 120K miles. So, 50% failure rate based on a limited sample.

 

I agree with your estimates, and so does fuelly. My personal experience is that I get better mpg in city driving, with certain criteria.

My comparison in my previous post was comparing driving alone on long highway trips (corporate sales) vs Uber type of stop and go driving with the added weight of 2 passengers and their luggage. My experience here is that the highway mpg will be better.