Oil change, brake and trans fluid interval for Prius Prime

IMHO, I would change the ATF, because your running mostly EV averaging 125mpg. That's a lot of heat cycling of the ATF in that hilly environment.
I really don't have an opinion on the engine oil change interval. It depends on how often that engine fire-up and for how long. The key is to use quality full synthetic oil - NOT JIFFY LUBE CRAP. There's a reason why places like jiffy lube recommend 3000 mile oil changes.

Hope this helps....

 

With that MPG, it sounds like you're getting at least half of your miles through EV. To me, that means changing the oil at 10K miles is like changing the oil for 5K miles of ICE driving (or better).

For me and my '19 Prime, my wife drives it 100 miles each working day, only 20-25 of this is EV. Your situation is even further skewed than mine as you get significantly more EV miles and probably drive shorter daily distances

Your question boils down to how much further can you push it since you're doing at least half of your miles under EV. A perfectly valid question,.

On one hand, it means you're really only changing the oil for 5K ICE miles. The EV miles shouldn't be used in the oil change calculation. and I've thought the same myself. It would be really nice if Toyota monitored the car's mode and discounted the EV miles when calculating the oil life remaining. Maybe also discount some of the regular Hybrid miles when the ICE is not being used.

On the other hand, changing your oil at 10K miles will mean you're inconsistent with your oil changes. If you go on an interstate road trip or, for some reason, you start driving further distances where you'll use more ICE miles, then you'll be closer to 10K ICE miles. There are some reasons why Hybrids (and Plug in Hybrids too) are harder on the motor oil. (I don't totally agree with this guy's video. I think the title is misleading and he ignores, until the very end, how Toyota has programmed their engines to run to warm up once they've been started, but there is a kernel of truth in there

).

Personally, I like the 5K mileage interval as I can look at the odometer and at any time I can quickly determine how much longer I've got till I need to change the oil. Yeah, it's more of a pain in the butt, but I'll opt for changing the oil at 5K miles. I also change it myself as I don't believe the quick oil change shops do a quality service for the extra cost (charging about twice what I pay for the oil I use, not replacing damaged or missing push clips under the car, and not checking some of the other things that need to be checked periodically).

It's your car, you decide what to do with it. Play it conservative, or try to stretch it, or somewhere in between (change the oil at 5K if you feel like you've been driving a lot under ICE or have taken a long road trip in the past 5K miles.

 

For transaxle fluid, you can't change it too soon, first time. Say one year or 10k miles. Thereafter I'd say you can slack off. This is judging from my experience, think I've done 3. The last one, it was hard to differentiate used fluid from new...

For brake fluid, Toyota Canada says 3 yearly or 48k kms (roughly 30k miles).

For oil change, just my 2 cents: if it was just a hybrid, yearly or 5k miles, whichever comes first. For a plug-in, not sure, time element I'd say yearly still.

 

FWIW; I do annual oil changes and calculated that I've got 7.5K on the ICE. These are very generous estimates/calculations skewed towards ICE operations for unknowns. I do about 12K miles a year and my lifetime odometer average is 139mpg. I do at least a monthly trip to the south Lake Tahoe region, so the engine gets a really good work-out, at least once a month. Sustained continuous operations for a few hours, for those trying to judge operations, distances and elevation changes.
The last few changes, oil was a light honey brown - difficult to tell it was used oil without a side by side comparison.

The brake fluid, I'd go 3-5 years between changes. Start testing at 3 years. Mine still test good FWIW. Going to do a full brake system flush on year 5, even if it test good.

 

As you're finding out, opinions on the topic are like ashholes.

First, you've got a 2017 Prime, so you should really be looking for info over here:
Prime Care, Maintenance and Troubleshooting | PriusChat
(you're currently posting in the gen 5 2023-up sub-forum)

Oil: I'm a staunch believer in 6mo/5k no matter how little you drive. I also would use Valvoline Restore and Protect oil to keep those piston rings clean. (it doesn't come in the 0W-16 that the gen 5 uses, but I'm considering switching to 0W-20 just so I can)

Coolant: If you haven't already changed coolant, do that ASAP. Never go beyond 5 years in order to protect your head gasket. You can do 5y/100k on the original coolant, but 5y/50k after that. The 5y is the important part. Coolant gets acidic over time and starts attacking gaskets, seals, and metals.

Transaxle fluid: It's probably time. The WS fluid in the eCVT can be changed anywhere from 6y/60k to 9y/90k. The Toyota eCVT might be the most bulletproof "transmission" currently being made. There aren't any wear/friction components to generate heat and break down the fluid, so it lasts almost forever. And since it's a very sealed system compared to most fluids, oxidation isn't nearly as much of a problem as it is with engine oil.

Brake fluid: The only way to know is to test it for moisture and copper. In environments that are always humid, you might have to change it every year or two. In dry environments, you might get five or more years out of it. Using a time or milage interval for brake fluid is worse than useless. It's either good or it's not, and only a test can tell you which.

 

What do you use to test the fluid? The dip strips or one of those electronic testers?

 

They test different things. The electronic testers test for moisture, the strips test for copper. You could say moisture testing is to try and prevent corrosion, while copper testing lets you know if corrosion has already started. Both can be important depending on the age/condition of the vehicle.

 

I wonder how homogenized the brake fluid is, say fluid from reservoir versus some bled from a caliper.

 

I've heard that water does makes it way down to the calipers, but then the brake fluid is slightly more dense than water. The hygroscopicity likely means a homogenized mix.

 

I use the electronic pen. Used to use chemical strips, but they expire and inaccurate if improperly stored. I just need to change the battery on the pen, every once in a while.

 

It is interesting, in the "recommended" maintenance (per toyota) for the gen5 prime, there is zero mention of replacing the automatic transmission fluid any time in the first 120,000 miles in normal operation. If we choose to do this anyway, on what interval is the consensus?

 

Toyota considers it a lifetime fluid, therefore on change interval. The question here is definition of lifetime. Engineers need parameters to specify maintenance intervals, so if the car's lifetime is defined as 150K miles - 95%-100% of the cars will make it to that interval, before failing.
The consensus for old style automatic transmissions was 60K miles or 30K miles under extreme conditions (ie. towing). Toyota's eCVT is NOT like an old school automatic transmission.
IMHO and experience with gen4 and prior Prius transmissions, I've found the ATF to be really dirty in as little as 20K miles. Subsequent ATF changes at the 60K mile interval was much cleaner than the initial drain & fill; so I would probably put-off the 2nd ATF change to 100K. I can only guess that initial break-in and assembly dirt was the cause of the initial dirty ATF.
Now your gen5 has changed to ATF TE from ATF WS, a less viscous, more watery ATF; so all bets are off. Make your own choice, but if it was me, I'd error on the side of caution and do a change to see where you are. If your letting a mechanic do the job, you'll probably be lacking the information needed on the next ATF change - don't have the necessary information to make a comparison.
I plan on driving mine into the ground, so replacing fluid that doesn't require changing, I consider cheap insurance and minimize internal wear.

Hope this helps.....

 

I'd do an early change, then stretch it. Say 1 year or 10k miles, then another around 10 years or 100K miles. Just based on the darkening of fluid I've drained.

 

We have the same opinion in the subject. I'm the "oil is cheap, engines and transmissions are'nt.." type of guy and a firm believer in early flushes to get the gritty stuff out, fast. Anyway, i'm going to change my ATF soon (surprised i have'nt done so allready but the new ATF is expensive AF, like 100$ for 4 liters..). I've allready put a magnetic drain plug on it (factory toyota part, can post the P/N if people are interested) and some metallic crap was allready sitting at the bottom of the old plug when i put the magnetic one on it. I didn't flushed the oil that time, only something like half a cup as i switched the plug. Definitely won't go over 60k miles between flushes..

As for engine oil changes, my gen 5 seems to be real hard on oil so i monitor it often and never go over 5k miles. Even as fast as 2k when it's very cold outside and oil gets diluted with gas/water...

If i ever get trouble, it won't be oil related..

 

Yikes!!! Please keep us informed of what you find and how many miles on the original ATF TE. Let us know how the 2nd change at 60K looks. I have a bad feeling that it's going to be dirty because it's thinner, meaning more wear.
Is the 2024 still at 0w16 or did it go down to 0w8 like the corolla? 'The oil guy' is already seeing higher wear materials during oil analysis at 0w20. He's doing a series on his daughter's car at 0w8; so we need to wait and see.

 

The thing is, grit in ATF comes from the friction rings that are part of the automatic transmission. An eCVT doesn't have those. AMD(The Car Care Nut) is currently recommending 6y/60k for the gen5 and I'm going with that. The only reason he's going as low as that is because TE is brand new and doesn't have a long service history yet. He recommends anything from 6y/60k to 9y/90k with the eCVT using WS. You can imply from his video on the subject that TE might very well be good for longer than 6y/60k, but he wants to see what it looks like at 6-7-8 years before he's ready to make that recommendation.

 

Where is good place for a DIYer to get a copy of the toyota guidance/torques/directions on draining/refilling a gen5 prius prime transmission?

 

Toyota Tech Info would likely be the option, till someone cadges some of these and distributes. FWIW Honda includes basics like this on owners manuals…

 

That requires an account and a subscription, correct?

I wonder if a local dealer would print out some pdfs of the procedure if I asked them nicely?
(or does toyota discourage this?)