Gen5 Prius -- EGR cleaning required?

shouldn't be, it wasn't on gen 4. it was really just a poor design/engineering choice that toyota finally corrected

 

Gen 3 EGR was poor and evidently untested, more's the shame. Gen 3 owners ended up being the testers, and Gen 4 revisions were the outcome.

Wouldn't hurt to pull the throttle body though, see what's lurking beneath. If it looks like a black/shiny mirror (oil pool, courtesy of PCV circuit), further investigation might be in order, and an oil catch can might be useful.

 

- No. EGR problems were fixed over a decade ago.

- No. Toyota uses port AND direct fuel injection. The port injection keeps the intake valves clean.

- With a Prius Plug-in, you want to have your A/C(technically the heat pump) checked more often. The A/C system in the PHEV also keeps the HV battery cool. With all the extra refrigerant lines and seals, it increases the risk of leaks. And it's critical to the long term health of the HV battery to keep it cool. The system will give a hybrid warning light if things get too bad, but an A/C check at 8y/80k is recommended in the official maintenance schedule. Honestly, there just isn't enough data yet to be certain there's any problem(not enough gen5 PHEVs have hit 125k+ to see any trends developing), but it's something to keep an eye on if you own one.

I'll also say that I'm a big supporter of 6m/5k oil changes no matter how little the ICE gets used in a PHEV. That opinion comes from long-time Toyota techs that are much, much smarter and more experienced than me.

My gen5 maintenance schedule:
6m/5k oil change
4y brake fluid(if moisture hasn't exceeded 2.5% yet)
5y/50k both coolants (you can go beyond 50k on the original coolant, but stick to 5y and then strictly 5y/50k after that)
6y/60k transaxle fluid (doubt it will hurt to go longer, but the new TE fluid is still really new, so not much data yet)
8y/80k A/C service(PHEV only) (I might consider dropping that down a bit to 7y/70k or less just to be safe)
change air filters as needed(depends on local conditions)

The brake fluid and transaxle fluid can likely go beyond those numbers, but I feel it's nice to space them out. By having one major fluid change per year, it gets you or a tech underneath the car every 12 months to keep an eye on things(suspension components, rust, fluid leaks, etc.). If you bundle all the maintenance together, it might be a few years between getting underneath for a major inspection, and that gives a lot of time for little problems to become big problems. But that's just my opinion on things.


The known things that can kill a gen5 powertrain as of now are:
- stuck piston rings from sludge (6m/5k oil changes and using a cleaning oil like Valvoline Restore & Protect if it comes in your viscosity; currently yes for 2023-25(0W16) and no for 2026 and up(0W8))
- acidic coolant eating head gasket coating, internal seals, and inverter internals (5y/50k coolant changes to prevent it from getting too acidic)
- overheating the HV batt (maintain A/C system in PHEV and regularly check HV batt filter in HEV)

 

Possible to do coolant/brake/trans(?) fluid changeouts based on test results?
What do you think about the dealer doing the maintenance?
I'm having them do 5k oil changes. Also 5k tire rotations (while in factory included maintenance.)
I'm coming up on 15k miles on the car, a '26 HEV.
At this point in my life, I don't think I'll be doing it myself.

 

My maintenance schedule is similar to Hammer but I don't get the A/C looked at unless there's a problem. (But I don't have any Prime vehicles.)

Don't forget about the hybrid battery cooler fan(s). There's an access door you remove and then can replace or clean out the little cloth filter. Also, shine a light in there and look at the fan to ensure it's not caked up with dust or stuff. (We have dogs so I worry about dog hair getting in there.)

 

The gen5 PHEVs don't have the hybrid battery cooler air filter anymore. They use the A/C to do it instead. I still have to check/change the filter in my gen5 HEV, but the OP doesn't need to worry about it in his new gen5 PHEV.

 

Coolant: It's my understanding that the pink Toyota coolant gets acidic at a predictable rate. That's why the 5-year interval. You can technically go up to 100k miles on the original fill, but the 5y rule still applies. This applies to both the coolant in the engine loop and the inverter loop(it's the same pink stuff).

Brake: I think you could absolutely go by test results. As long as the moisture content stays low(<2%), I don't think you have to change the fluid. I'm planning on changing it every four years or so just so I have an excuse to go in and have the car looked at by a professional. Ask a dozen car heads about brake fluid change intervals and you'll get a dozen different opinions. Some will change every two or three years, and others say you never have to change it and can go ten years or more. One note about Toyota hybrids is that their braking systems are a little more susceptible to problems because of the increased complexity of the actuator. So maybe lean to the lower end of the interval range. It's why I'm probably going to go 4y instead of 5y or 6y. But it's up to you. Just make sure to moisture test the fluid every year in a hybrid after the first three years(you shouldn't have moisture problems in a brand new car).

Transaxle fluid - Nothing to test here. The WS fluid in the previous gens was good for up to 9y/90k. The only reason I give 6y/60k for the gen5 is because the TE fluid is so new(came out in late 2022). I fully expect TE to eventually get up to that 9y/90k mark, but it's going to take some time to get data. But the eCVT transaxle is the most bulletproof part of the car, so I wouldn't get too worked up about it. I bet you could never change the fluid and the gen5 could still go 250k+ without a problem. If you want to go beyond 6y/60k to save a little money, I wouldn't blame you.

 

If you've got a plug-in(Prius Prime or Prius PHV) like your profile says, you don't have a hybrid battery filter. The gen5 plug-in uses the A/C system to run cold refrigerant(R1234rf) through pipes back to the HV battery. The standard gen5 hybrid(HEV) still uses a fan to blow cabin air across the HV battery to cool it, but the PHEV version no longer does.


On air filters:

Air filters of most any type(engine/cabin/HV batt) should be changed on an as needed basis rather than on a fixed schedule. The reason is that the rate at which air filters "decay" is directly related to the air that passes through them. If a person lives in an area where the air is clean of contaminants, those filters could last ten years before they need to be replaced. But if another person driving the same car lives in an area with tons of dust, smog, and/or pollen, they might have to change air filters every year or even less.

The HV battery filter adds another layer of complexity. It filters air that comes from the cabin. So if you live in a very dusty/smoggy/pollen-filled region but you maintain your cabin filter very well, your battery filter might last far, far longer than your engine and cabin filters. On the other hand, you might live in the cleanest air on the planet, but you also own pets that you regularly transport in the car and that shed heavily. In that case, your engine and cabin filters may last forever but your battery filter needs to be changed frequently.

The only exception to this rule is if you decide to use a premium cabin air filter that uses activated charcoal to filter odors. Activated charcoal has microscopic pores that trap contaminants as well as water vapor. Once a pore traps something, it's used up. And you can't visually tell how much activated charcoal has been rendered inert. So it's best to replace activated charcoal cabin air filters every year. Maybe even less if you notice a big difference in air quality when you install the new filter. (Also note that activated charcoal filters still do their regular air filtering even after all the charcoal is used up; they just won't filter odors anymore.)