Should I replace the transmission fluid on my 2008 Prius with 250k?

Sure won't, and a great idea. Easy dump and fill job, just be sure to loosen or remove the fill plug before you drain the fluid.

 

Yes, Toyota ATF WS. Best to stick with the factory fill to be safe, be it Toyota WS or Aisin WS.

Though many here have used nearly everything, from Valvoline MaxLife to Redline/Amsoil, and someone even used engine oil

 

It can't slip. Change it

 

If you don't mind: save a little of the drained fluid if you can, and do a side-by-side pic with new.

 

Your car does not have the kind of transmission that slips. It's a completely different creature. It does not shift gears and there really isn't a gearbox. It's an electric motor with a chain going to the final drive. Do replace it and do not worry about slipping (or anything else). I am sure it needs to be changed at 250K miles. Use the stuff you posted a picture of. It's important for it to be WS type because of said electric motor involved.

 

4 quarts or liters should be enough. Correct level is achieved by adding new fluid at the fill hole till it starts coming back out, with the car level. A funnel with about 3' extension tube is a dead simple method to get the new fluid in (with an assistant). Keep tube OD 5/8" or less and it should* fit. There's not a fluid change instruction in the second gen Repair Manual, but there is a check instruction (attached).

I'd recommend to have a preliminary look, see what the bolt sizes are, what's needed. I'm not sure what's involved with second gen, but 3rd gen for example, a 10 mm hex male "socket" is needed for both, and the torque is 29 ft/lb. A long handled wrench (or breaker bar) will be handy, they tend to be glued on. Also, replace the washers: dealership parts department should be able to figure it out.

Don't shoot me if it doesn't, I've not done a second gen. Again, a prelim scouting expedition would be good: you can check what sort of sockets are needed, and maybe remove just the fill bolt, check the ID of the hole. A slight amount of fluid might spill out, especially if the car is tilting backwards. But not much.

Oh, and: I've seen a Toyota document that recommends to only use fluid from freshly opened bottles.

 

This is not as good as the NutzAboutBolts video for the Gen 3 but here is the best Gen 2 video I know of.

www.amazon.com/Genuine-Toyota-Automatic-Transmission-Standard/dp/B00CTUSEMU

www.amazon.com/Aluminum-Washers-Highlander-Replacement-90430-12031/dp/B071SKK88V

Toyota engineers hint it should be changed every 100,000 miles, but anytime is a good time.

 

FWIW

Prius "c" uses same 10mm allen, same engine as Gen2, although maybe diff trans?

Also, I do remember some thread here saying after a high mileage trans drain and fill,
they jumped up in mpg. not sure if anyone else remembers.

btw, just noticed you are near me @Banksy
Let me know if you need a hand or tools.
may also have one quart left of WS

 

Honestly I wouldn't bother. The point of changing it at all is to do it early enough that the extra particulate contamination has less of a wear effect later in life. So there's some logic to dumping it at 50k and maybe having one fewer problem once the thing has 250-300k on it. But only maybe, since Toyota says its good for life and for the most part hasn't been wrong.

Well you're already there at 250k. There is obviously some more dirt in your oil now, and the car didn't have a problem. In other words, you've already received 80% of the benefit for free, why pay for new oil now? Keep the cash for the next thing. There will be a next thing.

I certainly understand the desire to protect and maintain a car, but there is a lot of cost in over-maintaining something. You might say it's even enough to sustain a network of neighborhood car parts stores and retail sales of clever formulas.

This is one to skip.

 

I am going to (respectfully) disagree with Leadfoot J. McCoalroller. lets get those suspended metal particles out of your transaxle before they short out a motor. "Pay me now or pay me later" is $100 vs $5000.

Just my 2 cents.

 

That sounds pretty good then, if you saw some red tint to it.
Sounds like it may have been changed at one time.

But years of the plug in there, with water, salt, hot, cold makes them tough to remove.

 

You'll almost never see much in there, there are no clutches or friction bands shedding particles in a Prius transaxle, so the fluid stays vastly cleaner than traditional automatics.

 

They probably were torqued to 29 foot pounds, at the factory. Any bolt will take a lot more fight to break loose, especially as the years mount. Again, a long-handled wrench helps.

 

Party Pooper.
That's a brilliantly logical argument for NOT doing it. I've got to applaud it.
But I'm still going to side with doing it.
Mostly because the OP seems like they are (have done it) going to do it themselves, so we're not talking a big expense here. The labor is the OP's, and the only cost is the fluid itself.
So in this case? Even though you are correct in pointing out the potential benefit of changing it vs. an earlier change point scenario, is lost, I still think a change could be better for the transmission. Worst case, it doesn't hurt anything or help anything but the fluid is new.