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Because they're older, my in-laws have been in quarantine since early March and haven't driven their car at all. It's been sitting in the driveway in New Jersey (USA) the whole time, in mostly above-freezing and then warm and hot weather.

The car is a 2012 Subaru Forester and it's always been very reliable. Now it won't start, probably because the battery is dead. We could jump start the car, but if it does start and operate as normal, is there any other reason not to just drive the car for a while after that?

Some sources say to drain the gas and all fluids and replace them before driving, but that would be a lot more effort, obviously. Is it necessary to do so?

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Cars are routinely left parked for three to six months or more without running, with no ill effects. I wouldn't hesitate to jump it and see if it'll start. As @BrianKnoblauch comments below, jumping a completely flat battery risks the alternator. The risk can be ameliorated by using a battery charger first, or leaving the jump battery and the to-be-jumped battery connected for a time, so the flat battery has at least some charge before the starter is engaged.

If the battery was old when the car was parked, however, the just-sitting may have pushed it over the edge into failure. That is, you might be able to jump it into running now, but the battery won't start the motor on its own the next time.

The low-tolerance-for-risk solution is to replace the battery. If you or your in-laws want to gamble on getting stuck, make sure the battery is fully charged, either with a charger, or by driving the car a significant distance. Without figuring alternator capacity, I'll guess that "significant distance" means an hour at engine rpm well above idle.

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  • Given enough time, I'd charge the current battery on a charger, then see if it starts the car, as a test. Then try to remember when the weather turns cold that the battery may still be marginal if it starts the car in summer – Chris H Aug 20 at 10:56
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    You also risk the alternator by jumping a flat battery and then making the alternator work hard to recharge it. Alternators are meant to keep batteries charged, not bring them up from nothing. I'd definitely use a battery charger. – Brian Knoblauch Aug 20 at 16:14
  • @BrianKnoblauch A good point, thanks. I'll edit it into the answer. – DavidSupportsMonica Aug 20 at 16:58
  • You can minimize the risk of getting stuck if the battery is toast by having your initial test drive be circling around the block x times before returning home to turn the engine off. – Dan Is Fiddling By Firelight Aug 21 at 13:49
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If you have the ability and access to some tools, remove the battery and bring it to your local national auto parts chain ie: AutoZone, AdvanceAuto Parts, Oreillys etc. You may want to call first to see how they are handling this during Covid. They will charge and test the battery to determine its condition generally for free. This will take several hours or possibly overnight. Reinstall the battery. You may want to cycle the ignition key from "off" to "on" several times before attempting to start the vehicle. Start the vehicle as normal. Let it idle for a minute or two until the engine idles smoothly. Drive slowly (25-35mph) around the block for a few miles to warm everything up and get the fluids circulating. Gently apply the brakes several times to remove any surface rust from the rotors. If everything seems ok find the owners manual and check the maintenance records. If it is due for service based on time or mileage then schedule that service. It may be due for an oil change because it has been a year since the last one.

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    The issue with just jump starting is that if the battery is really dead it puts a lot of load and wear on the alternator to bring it to a full charge. Additionally you won't know the condition of the battery and if it will start the car the next time. If you have it charged, it can be tested and if need be a replacement can be purchased. – mikes Aug 19 at 23:30
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    Anecdotally, I have discovered during lockdown that once jumped my otherwise good condition flat battery needs a good half hour of driving every week to prevent it going flat again. That's now become part of my lockdown routine. No failures at all since I started doing this. I think my first run was an hour, but a half hour or so ever since has kept it reliable. – Tetsujin Aug 20 at 9:55
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    @Tetsujin similar here, only I'm lucky enough to have a 20W solar panel and regulator anyway. It's not going to give 20W on the dashboard, but it doesn't need to just for topping up. I can easily hear when the battery is weak, as a 2.4 litre diesel takes a fair bit of cranking – Chris H Aug 20 at 11:05
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    @ChrisH - Yeah. I don't have anything like that, though I do park right next to a service garage who have a nice jump starter. Normally they could full-charge my battery, but their 3-phase is down so no can do right now. I do appreciate the amount of power needed to turn over a big engine - 3L v6 here ;) I quite enjoy getting out of the house for a random direction drive to nowhere once a week though. – Tetsujin Aug 20 at 11:09
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    @ChrisH - it would be considerably more trouble than its worth on a modern 'all computer' car. No alarm, no motion-sensing camera, no locks, no clock, CarPlay, Bluetooth needs setting back up, etc It also really upsets the MIL. Even flattening it far enough that the electronics work, but then drop out as you attempt to start it means I need to reset half the above, then the MIL - for which I had to buy an app on my phone & a dongle for the car's diagnostic socket. – Tetsujin Aug 20 at 13:22
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One thing I would do is check all the fluid levels before starting it, even if only to drive it to get it serviced. Also the tyres may need some air. My brake discs rust easily in our wet climate, so I know after even a few weeks to be wary of them at first. A few uses from very slow will tell you if they're OK and getting back to normal.

As I commented, I'd ideally charge the battery from a dedicated charger before starting the car with it. If it fails that test you definitely need a new one. If it passes, you still need to be careful when the weather gets cold as batteries don't like being kept discharged. Luckily failing to start is most likely when the engine is cold at home, reducing the chances of a stranding.

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    This is good advice, but a Subaru from 2011 will already do this for you. Just check the dashboard for any warning lights. If there are none, you're good to go. Cars include all that expensive tech these days for a reason. – user91988 Aug 20 at 16:40
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    @user91988 does it actually check the levels and not just oil pressure/coolant temperature etc? The newest car I've ever owned was 2008, anything newer has been rented or borrowed; the work car from 2014 doesn't check everything as fully as you imply. I have a bit more experience of tyre pressure sensors - they're more of an alarm than a measurement, and a pain to reset, so better to check manually. Anyway I'd like to check before turning over the engine – Chris H Aug 20 at 16:56
  • Depends on how much time and effort you're willing to spend on something that's very likely to be just fine. (It's only been a few months...) I think most of us don't consider the risk great enough to bother. Cars are very well made these days, despite what old school gearheads want you to think. – user91988 Aug 20 at 17:11
  • @user91988 10 minutes well spent if you ask me. The battery is key though as modern gadgets run them down faster when not in use, and being stored empty harms the battery – Chris H Aug 21 at 12:21
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One other thing to check: regardless of the amount of gas in the tank:

Actuate the gas gap release lever NOW. You want to be sure the cap will open, while there is enough gas in the tank to get to a mechanic in case it doesn't.

My 2010 RAV4's release lever seized, after only 6 weeks of non-use at the start of the pandemic.

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  • It's a good idea anyway to refill your gas tank while it's above a quarter tank to avoid a premature death of your fuel pump, which ought to be enough to get you to a mechanic. – Kat Aug 21 at 18:17
  • What a "gas gap release lever" and how to I find it on my Passat? (I assume it is not limited to LPG carsl – Ian Ringrose Aug 22 at 18:19
  • Many North American cars have a locking cover over the gas cap. The cover is spring-loaded, and unlocked by tugging on a cable lever inside the car. Pull the lever, and the cover pops open, allowing you to unscrew the gas cap and fill your tank. But in Canada where I live, we get snow. And the city melts ice using salt. This means rust. And if the cable connecting the gas cap release lever to the cover gets enough rust, it will bind up. Not a problem if you are popping the cover every week or two as part of regular fill-ups, but... – d3jones Aug 22 at 19:11

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