5k Gen 3 Prime — Milky oil

Nice shot of the engine bay. Looks like Toyota moved some stuff from the drivers side to the passenger side when compared to the Gen 4 Prime. At least from what I can see in the pic.

 

I am so relieved to hear that this milky oil issue is a known thing on Prius. I nearly freaked out when it came out milky greenish brown and was sure I had a head gasket problem. Was about to order a kit for a block test. I was admittedly a bit peeved when the Toyota tech looked at it and said it looked normal to him. I'll chill out and sit tight until a 5k change and see what it looks like then. Thanks!

 

So if in doubt - would it be better for the car to have a shorttrip either in ev or charge mode - instead of using HV mode?

 

I think in a cold climate it may take a lot to actually get the engine hot in the winter. In a Prime it may be off more than realized, not resulting in the desired burn off the water effect. The propulsion screen or whatever it called shows when the engine turns off even on the highway. I suppose a scanner could be used to see temp on a phone. So more to monitor, battery, water temp, what’s next?
I’m a little surprised the dealer tech’s don’t do a water/oil temp drive test. Not sure what taping the covers does. Afraid the owner is tampering?

 

Short trips in the Prius Prime should be made in the BEV mode, which is the default driving mode. That avoids ICE problems arising from short trips and reduces cold-engine emissions. Moreover, the BEV mode is far more efficient in the city than on the highway.

 

Its been below 0 most of the time I've had the car, a month and 1100im, 350 on the engine.

Checked oil today and it was super clear and clean.

But I'm trying to break in the engine. So I do run it intentionally a bit more ofren. So probably for you just not running it up to temp enough.

I think the issue with low run to.e to warm up is probably from hitting the end of Bev range and only doing a short time on engine.

Personally if I see I will be on HEV for only a few minutes at the end, I switch to hev early. O ly happened twice so far.

 

I’m surprised people aren’t a bit more concerned with this milky oil issue. Some of the cited temperature conditions don’t sound very cold to me, such as 0celsius. I don’t seem to hear any mention of Gen 4 engines having this difficulty. I live in cold Alberta and would think my Gen 4 would be prone to the problem of the engine not heating up well on my short commutes, but it hasn’t shown any hint of this. And, I’m used to the oil in different Toyotas I’ve owned being very clean looking at the time of oil changes, especially with synthetic oil. I would be very unhappy with a new car exhibiting milky oil, personally. Wouldn’t that mean that engine lubrication is sub-par? Has anyone with Gen 5 had this problem in the absence of cold outdoor temps? Is it only Prime models?

 

Guess we'd need someone in Southern California or other warm climates to check their oil.

 

Milky oil simply means too much moisture in the oil and the engine never getting up to operating temperature long enough to burn it off. Have only heard of a couple examples of that happening so don't think it's an issue with the engine itself, just how it's being driven. Also keep in mind that oil takes longer to reach operating temperature than the coolant. Where I live, it rains practically every day it seems lately and I haven't had any issues with the oil.

 

Yes it would be better. If you're using HV mode for short trips, you're lucky to get only 30-35 mpg because the engine is cold. Save the HV mode for longer trips. The Prime manual even states it's best to use EV mode in the city and HV mode on the highway/freeway..

 

To be fair the part about highway and freeway also.has the caveat of "if you can't make the full trip on EV". So save EV range for city if the trip can't be done in full on EV. HEV is more efficient to force at highway speed than happen for city drive portion.

 

Of course sometimes that is out of the users control. For instance my commute is less then 5km. When it's below freezing as much as I'd like to make the short drive in EV mode, the car turns the engine on and it runs for less then 5 minutes. I wish I could force the car not to do that but it can't be overridden.

 

So what does the G5 do to warm up the engine faster? G2 had the thermos bottle, G3, 4 the exhaust heat exchanger, as everyone here knows.

 

I'm not sure. I do know that I've had it kick on and it won't turn off the engine before the temp is appropriate and it runs a minimum amount of time.

So if the defroster turns on in EV mode, starts the engine, and even if I turn off the HVAC and defroster, etc. The engine won't turn off unless I turn the car off, even with the EV button selected.

So it's possible there are situations where people just shut the car off too quick after it hits HEV mode. Or they force switch it back to EV by restarting the car? I don't know.

As for preheating - I'm not sure how much that helps the oil? Like, the engine will have condensation when it warms up and it was cold. The engine just sitting at a steady ambient temp won't really introduce much condensation at all, not to the point of milky oil I don't think.

The user manual isn't clear but it does say not to worry about warm ups, and engine on off related to warming up as it's designed to do that and that cold starts/warming up isn't a thing to bother with. This makes me think there must be some system for a base operating temp for the oil to be at an appropriate viscosity. But an appropriate viscosity and lubrication point is very different from hitting the necessary temp to boil off condensate that builds up. For that, the minimum run time the car seems to employ is probably the thing that deals with that.

It's the interruption of this minimum run time that's probably causing milky oil.

Maybe if the car put up a sort of notification on min run time for oil, it would help drivers be more aware? If someone happens to always cut that short due to a quirk of their daily commute - that's probably the cause. And it's probably why it's talked about but not so common as to have a Toyota response or other manufacturer response either. It might also help if the user manual explained "when the range is insufficient to complete your full commute it's not only more efficient to use HEV on the freeway, but it also ensures minimum engine run time in cold or humid environments allow condensation to evaporate from the engine which after repeated short, cold start runtimes, may result in oil contamination and a milky appearance" or something to that effect.

 

Actually it can be "overridden" but it's a timing issue. If for example, if you know when you would be driving, you could plug in the AC charger to time it to be fully charged before you're trip. Plus after it's fully charged, the battery heater would be periodically engaged to prepare it for use. Once a week, I drive into Portland and temps have been regularly below freezing. Since I charged the car overnight, the battery is fully prepared and I can take off in EV only mode. I engage HV mode when I leave the town I live in and on the highway.

 

@Rafsdhc6 , ask the mods to revise the title, to say "2023 Prius Prime - MIlky Oil"? Current title is bewildering.

 

I leave the car plugged in overnight to charge so it's 100% charged and when it's bellow freezing the engine will start after driving about a block.

 

Do you have the defroster on? That forces the engine on. So if it's cold enough that might be it?

Below freezing my engine doesn't come on unless it's using the front defroster or I crank the heat really high. If I have it set to 21c for example, the engine stays off even down to -10c

 

Nope, no front defrost on. I usually have the cabin heat set for 20c and just turn the heated seats on if I get cold.

 

That doesn't happen with mine but you can certainly hear the heat pump roaring when it's cold out. One thing I rarely do is engage the windshield defroster which may cause the engine to turn on. We'll see what happens on my weekly trip into Portland on early Wednesday morning this week. It's supposed to be below freezing.