I purchased my 2009 Ford Ranger 4WD last October, it is now 8 outside in Indiana and will bet below zero for the next few days.
My question is how can I make sure it will start?
Do I go purchase a block heater or a trickle battery charger or just cover it with a blanket? I do not have a garage and am in Central Indiana.

 

I'm in central OH and will have pretty much the same temps.

- In a short squeeze situation you could go start it every 4hrs and let it run / warm up for 20 minutes. (heat in the engine is most important. So no need to run the heater in the cab)
- Jump start it
- Take the battery inside

Some farmers (in the old days) would drain the oil and take it inside at night.

My ranger is in the garage and I'm driving the lease car this week. It didn't start last week and I think the next 2-3 days I'll have to jump start it.

 

Couple of things

One is the CCA(Cold Cranking Amps) rating of your battery and its age
A new battery will have 12.8volts, 100% CCA rating
3 year old battery 12.5volts, 75% CCA rating
5 year old battery 12.3volts, 50% CCA rating, and the dreaded "click, click, click" on a real cold morning will occur

12.2volts or less is battery that is done.

Starter motor takes about 70amps to crank a cold engine over, batteries release amps slow when they are cold, so double whammy in very cold weather
On top of that when cranking is hard the voltage in the vehicle drops down to 9volts when cranking, so weaker SPARK for starting.

And the second part
Gasoline can't be ignited by a spark, yes the movie guys take liberties, lol
Only gasoline VAPOR can be ignited by a spark
And you need about 30% Vapor in a cylinder for it to be ignited by a spark plug
This is why cold gasoline engines need to be Choked, Choke just means adding more fuel than when engine is warm, that's what Choke Plate did on a Carburetor, it reduced air flow so more fuel was sucked in from the Jets for cold starting, computer does this for fuel injection, adds more fuel when engine is cold.
So a Rich fuel mix for cold start, so you need a good HOT spark, but you can have a weak spark if battery voltage drops too low

Gasoline has very little vapor below freezing, if you can't "smell" it there is no vapor, because thats what you smell, the vapor

Compression is there to heat up the gasoline, so as you crank the engine each cylinder gets a little warmer from its compression stroke and this helps vaporize some of the incoming gasoline
When it gets to 30% vapor it will start
But that can take extra cranking and you are back to the battery issue in cold weather.

You can use Starting Fluid, which is Ether in a spray can, ether has a very low vapor point, lower than gasoline, which is why its a good starting fluid, lol
A quick spray of ether into the engine will get it to start and once started the cylinders get HOT instantly so gasoline is vaporized enough to keep engine running.
You can pull off the power brake boosters vacuum line and spray ether into that hose, engine will suck it in when cranking, or PVC hose which ever is more convenient
I don't recommend spraying it to the air filter box because of the MAF sensor, repeated use of ether will require repeated cleaning of the MAF, it won't hurt it.

Block heater is best long term solution if you can plug it in, this keep engine and engine bay slightly warmer, so faster cranking and faster vaporization of the gasoline = better startup
And on the plus side heater starts to work faster, lol.
You can get heaters that install on lower radiator hose, but the ones that replace a Core plug(freeze plug) are best, IMO

And if you let engine warm up in the driveway be sure to LOCK the truck, have an extra key, thieves do look for that exhaust smoke in driveways this time of year

 

It was -2F here this morning and my 2017 CRV barely started. It was clicking and the lights were flickering like close encounters of the third kind! It started though.