I am currently trying to see what would be the most reliable. I’ve kinda hit a dead end with Honda and Toyota where 99.9% of the sellers are flippers selling me something that isn’t worth 6k. I’ve heard the Fusions are somewhat reliable. I’m mainly just trying to get something that will last me 2-3 years if I take care of it. I know Ford isn’t known for having reliability at all, but I know some of the Fusions were okayish.
Anything with the 2.5L engine and a well-functioning/upkept transmission should be worth considering.
The other drivetrains can be fun, especially the bigger ones, but for your price and reliability expectation, it’s gotta be the 2.5.
@Ren
1000% agree^^
Anything 2010-12 2.5L under 150k miles is worth up to $5k IMO. If your budget is 6k, look in that 10-12 range but lower mileage—you’ll definitely find something nice if you’re set on the Fusion and it’ll easily last you 5 years or more with good maintenance. They’re cheap on gas, oil, and maintenance all around and, best of all IMO—they’re easy to work on yourself at home, no electronic headache, no special procedures, all straightforward, and relatively cheap parts. Tons of vids online too. The biggest thing to watch for is the transmission, so try to test drive a few to get an idea of any differences between one Fusion and the next. Asking the seller about any past transmission services doesn’t hurt, but I wouldn’t bet they have any receipts or even an idea about that.
There is nothing for 6k
I’m kidding.
In all cases, you will be looking for the same engine: 2.5, that can make 200k without breaking a sweat.
You have the older style, 2010-2012, with about 140k miles, for about 5k
Or the new one, 2013-2016 for about 8k.
Slightly nicer on the outside, and (usually) much nicer on the inside is the 2017-2018 for about 10k.
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The second option is the 2.0 Turbo, a bit less reliable inherently. It can also make 200k, with a bit better economy and a bit more sportier feeling. Usually, slightly better trim level as well.
Those are about 500 dollars more expensive than 2.5L (2013-2016)
Wild Card, Lincoln MKZ, that is 500-1000 dollars more than Fusion (same year, same engine, same mileage).
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If you have 6.000, I would buy 2010-2012 for 5.000 and I would be ready for the tires (500), battery (200), DASH and REVERSE Camera (150), full tank of gas for 40, a nice dinner for you and some girl for 60, and you can do some alignment for the remaining 50.
And there you are - 6000 
The simpler the better, IMO. No EcoBoost, no AWD, no sunroof. In my experience, it’s the accessories that break on Fords; with good maintenance, the drivetrains will last a long time.
Just found my son a used 2009 Fusion SEL with 91K miles and negotiated it to $5800. It has a slow oil leak they weren’t aware of until it had been parked and not driven for a while, so I was able to get them down a couple of hundred. Other than some moisture in the headlights and needing a turn signal bulb, it was a clean car with only some very minor dings. They did have a fender bender repaired also, but the car looked and drove very nice! So far, he’s loving it. We plan to do the transmission fluid soon, but I’m hoping it lasts him many years.
If you can find a pre-2013 Fusion in decent shape with a reasonable number of miles, they all had good engines (2.3, 2.5, 3.0L). Aisin transmission would be preferable to the 6F35, but if you drain/fill the transmission fluid regularly on the 6F35, it will last. If they salt the roads where you live, something this old is likely starting to get pretty rusty, so watch out (not that cosmetic rust really matters, but everything underneath the car does).
With newer (2013+) Fusions, I would only buy the 2.5L engine if reliability is your main concern. The transmission would be the weakest link (they all have the 6F35), but again if they’re maintained, they will last.
IMO your best bet is to spend that amount on a really clean, low mileage 2010-2012 model. 2.5 or 3.0 are pretty reliable, slight edge to the 2.5 if you don’t make it run hard. They came from the Mulally (CEO) era at Ford when they were genuinely trying to chase down Toyota/Honda quality. Those years will have better mechanical simplicity than 13-15 should anything break down, and lower insurance costs too. Probably can find a very nice one under budget and keep some saved for emergencies.
10-12 with a low mile 3.0 or 2.5.
From my research, the 2.5 hybrid is the most reliable drivetrain option. However, others have stated that the 13-16 hybrid can face an issue with bearings. My notes state that cars were affected up until August 15, 2015. I would suggest a Panther body vehicle, Grand Marquis or Town Car specifically. I am about to look at a 2012 MKZ hybrid for around your budget. I chose not to get a V6 because of their internal water pumps. Local shop quoted me 4,300 to replace that and the timing chain.
I bought my '14 1.6L SE 6 years ago today, and it shows no sign of dying any time soon.
Be careful. Do your research. I ditched my '17 Fusion for a Toyota Venza. Loved the car, but my engine and transmission failed within a year apart.
Make sure they show you that the transmission maintenance was done. My transmission went out at 80k miles. 2017 Fusion SE. Not fun.
3.6 2007.
Great car. Less than $6,000.
Any low mileage 06-09 with a 3.0 V6. These have the good transmissions in them. 177,000 on mine, still very, very strong.
I can’t speak for any of the others as I have not owned any and have zero experience with them.