Thanks for the good information. I perform oil change just before the winter (Nov) then another change after winter (Apr). I believe winter months are most favorable for fuel dilution.

 

Thanks for the info and adding to the knowledge pool! I appreciate you noting that yours is an unusual scenario (where you start on a hill which causes your engine to kick in before fully warming up), but this is good info nonetheless. I’ll keep an eye out for similar fuel dilution issues going forward just to be extra safe.

Cheers!

 

Thanks for sharing. I've always done 5k or 1 year intervals. Hopefully that's good enough to avoid problems.

 

Nice analysis. I don't do many short trips, but I do stick to 5k intervals on mine. I may have to do a UOA and report back as well just for giggles and grins. Thanks for sharing.

 

Thank you. It is nice to get some real data rather than opinions.

 

If you get a future oil analysis done you should inform them that you have a A25A-FXS engine, not a 2AR-FXE as that can skew their data set that they use to provide real world comparison results to other engine owners.

The findings show that fuel dilution can be a problem for some, but I caution others not to make a blanket statement that every A25A-FXS has that problem. Most of my gas engine running is at highway speed for hours (except in extreme cold winter times there are shorter colder trips). So in my case, the fuel will burn off from the oil regularly. Yes if you have lots of very short trips any engine will have more fuel dilution than normal.

For a test next time you get an oil analysis done, go for a 30-60 minute highway drive in HV mode prior to changing the oil and see if that's enough to take care of the dilution issue.

How often do you drive on the highway in HV mode for at least an hour?

 

For a test next time you get an oil analysis done, go for a 30-60 minute highway drive in HV mode prior to changing the oil and see if that's enough to take care of the dilution issue.

That would not reflect the reality of the actual condition. That engine is dealing with fuel dilution issue because of driving conditions.

 

And people laugh at using 0w-20 or running intervals less that 10k miles in this engine…

 

Who is laughing at you? Tell him/her that Cousin Vinny is not laughing.

 

I live on top of a very steep hill. I can't leave the house without ICE kicking in if the battery has anywhere near a full charge. To effectively use this car as an EV it almost always runs its warmup cycle every time I depart, but the engine is seldom used otherwise unless I'm on a trip beyond EV range. This creates a large # of short cycles on my engine.

Is your commute that short that the ICE is unable to fully warm up?

 

Depends on definition of "fully." It runs it's warmup cycle for about 2 min (which kicks off just over 100F per the ScanGuage). Then it shuts off and I'm in EV until the battery is depleted. When this happens 50-100x per month it's like accumulating many many short trips on an ICE car. And other ICE's with direct injection would definitely dilute (I know my Honda does).

Several times a week we're beyond EV range and I'd consider those trips "fully" warmed up- anything from a 30 minute trip to long distance (hours). But it doesn't seem to boil off all of the dilution from the short cycles.

I think it comes down to the ratio of engine time in a cold state vs a warm state. It just so happens in my use case the engine is cold a lot. I wish there was a "don't run the damn engine until I tell you to" button I could push. That would solve it

 

Thanks for this information.
I’ve seen lots of people saying breaking in isn’t necessary anymore and going to the 10k oil change is just fine. Seems like flushing that iron and copper would be good.
Was this you’re first oil change? I’ve been very curious about the brake in period for these phev’s. Most of these engines are used so differently from normal ice engines. My commute is hopefully ideal for braking in the engine. I have 25 miles of country roads. Some stop signs and traffic lights, but mostly 45-60mph roads. I run in hybrid mode to work and charge the battery and drive home in ev. That way the engine warms fully and runs for a healthy period of time to properly set the oil rings. I will do an oil change at 5k, 10k, etc.
I’m very curious about people trying too hard to save gas and eventually shooting themselves in the foot no caring for the gas engine.
Thanks for the data!

 

The more I think about this, the more I think something is very strange going on. At the risk of starting an argument (and WW III), I offer my thoughts:

1. There is a known issue with moisture (water) in the oil, enough so to have T-SB on it: New TSB Regarding Milky Oil, Low Pressure Warning and... ( https://www.rav4world.com/attachmen...com/attachments/t-sb-0104-21-low-oil-pressure-milky-appearance-dtcs-pdf.175215/) The cause of this is short drives which don't allow the ICE to fully warm up, thus any condensate gets trapped in the oil, causing a milky or foamy oil. The solution is more frequent oil changes. This occurs mostly with hybrids and Primes since their ICE is used even less than an ICE only vehicle. Oil can accommodate some moisture, but when it gets excessive, in below freezing conditions, the moisture will freeze and block the oil circulation. Yet, the OP oil analysis shows zero water in the sample. Strange that the analysis shows so much fuel, which has a much lower evaporating temperature, and no water, which has a much higher evaporating temperature.

2. So that begs the question: where is all that fuel coming from? As the OP states, the oil level shows 1/2 quart high. That is two cups of fuel! That is a lot of fuel! The OP speculates that it is coming from the direct injection, which would mean a lot of incomplete burning, which is getting past the piston rings into the oil (and not going out the exhaust to be combusted by the catalytic converters). If the ICE is not even running, due to the downhill nature of the commute, there can be no fuel used; so if no fuel is used how can there be any incomplete burning, and getting past the piston rings into the oil? Very strange.

3. Is there another path for fuel to get into the oil? Perhaps through the EVAP system? (The engine crank case and the gas tank are connected together by the EVAP system). Is there a malfunction in the EVAP or fuel system that would allow fuel to get into the oil via some route other than the fuel injectors? Can the fuel injectors, either the port injectors or direct injectors, "leak" when the car is off, allowing raw fuel to get into the combustion chamber and thus the oil?

Any thoughts by the more technically minded?

 

The more I think about this, the more I think something is very strange going on. At the risk of starting an argument (and WW III), I offer my thoughts:

1. There is a known issue with moisture (water) in the oil, enough so to have T-SB on it: New TSB Regarding Milky Oil, Low Pressure Warning and... ( https://www.rav4world.com/attachmen...com/attachments/t-sb-0104-21-low-oil-pressure-milky-appearance-dtcs-pdf.175215/) The cause of this is short drives which don't allow the ICE to fully warm up, thus any condensate gets trapped in the oil, causing a milky or foamy oil. The solution is more frequent oil changes. This occurs mostly with hybrids and Primes since their ICE is used even less than an ICE only vehicle. Oil can accommodate some moisture, but when it gets excessive, in below freezing conditions, the moisture will freeze and block the oil circulation. Yet, the OP oil analysis shows zero water in the sample. Strange that the analysis shows so much fuel, which has a much lower evaporating temperature, and no water, which has a much higher evaporating temperature.

2. So that begs the question: where is all that fuel coming from? As the OP states, the oil level shows 1/2 quart high. That is two cups of fuel! That is a lot of fuel! The OP speculates that it is coming from the direct injection, which would mean a lot of incomplete burning, which is getting past the piston rings into the oil (and not going out the exhaust to be combusted by the catalytic converters). If the ICE is not even running, due to the downhill nature of the commute, there can be no fuel used; so if no fuel is used how can there be any incomplete burning, and getting past the piston rings into the oil? Very strange.

3. Is there another path for fuel to get into the oil? Perhaps through the EVAP system? (The engine crank case and the gas tank are connected together by the EVAP system). Is there a malfunction in the EVAP or fuel system that would allow fuel to get into the oil via some route other than the fuel injectors? Can the fuel injectors, either the port injectors or direct injectors, "leak" when the car is off, allowing raw fuel to get into the combustion chamber and thus the oil?

Any thoughts by the more technically minded?

The oil analysis shows 2.5% fuel. That equates to Full oil at 5qts=160 fl oz. 1/2 quart is a pint or 16 fl. oz. that would equal 10% of full oil. The real answer is 4 fl. oz. or 2.5% Unless I'm missing something, the oil analysis suggests a reading of < 2.0% is within a reasonable range, given no fuel in the oil at all would be preferable.

 

Gonna be real interesting. I think all the PHEV vehicles that use the ICE "sometimes" could be at risk for this. The O.P commute (Chuckles70) is really not a commute! He's got the worst scenario, and honestly, one that could affect even a pure ICE or Hybrid vehicle.

Something to bear in mind: ICE engines actively control the coolant (antifreeze) temperature. But for the most part, the engine oil is on its own. Now, it reaches a steady state, somewhere in the 300 - 400 degree range, depending on season. At that steady state, it loses heat out the crankcase, and more importantly, to the actively cooled (water jacket) parts of the engine.

At 300- 400 degrees, the water and fuel are evaporated off in short order. But takes a LOT longer for the oil to get hot than it does for the engine coolant to get to its 220 F or so (pressurized systems often run OVER the boiling point, for better heat transfer and besides, the ethylene glycol, in correct ratio raises the boiling point). The engines thermostat isolates the coolant in the water jacket from the radiator until its up to temp, so its a pretty rapid process for the coolant. But the oil take a lot longer.

Why do I know/care so much about this? Well I have a couple antique vehicles that I run once in a while. Among the old car enthusiast community, its considered kind of gospel to never start a vehicle unless you intend to fully warm it up and run it for a while.

Seems to me that for folks like the OP, you are going to need to purposely put it in whatever mode causes the ICE to run the most and warm it up good and proper once in a while. Another poster described their process for this. I don't have my Prime yet to have any personal experience.

Finally, I tend to agree with a number of comments here and in other threads: there ought to be a setting where the ICE just plain was blocked from kicking on, or at least would throw nasty warnings that whatever you are asking the vehicle to do will soon result in ICE starting.....

 

Gonna be real interesting. I think all the PHEV vehicles that use the ICE "sometimes" could be at risk for this. The O.P commute (Chuckles70) is really not a commute! He's got the worst scenario, and honestly, one that could affect even a pure ICE or Hybrid vehicle.

Something to bear in mind: ICE engines actively control the coolant (antifreeze) temperature. But for the most part, the engine oil is on its own. Now, it reaches a steady state, somewhere in the 300 - 400 degree range, depending on season. At that steady state, it loses heat out the crankcase, and more importantly, to the actively cooled (water jacket) parts of the engine.

At 300- 400 degrees, the water and fuel are evaporated off in short order. But takes a LOT longer for the oil to get hot than it does for the engine coolant to get to its 220 F or so (pressurized systems often run OVER the boiling point, for better heat transfer and besides, the ethylene glycol, in correct ratio raises the boiling point). The engines thermostat isolates the coolant in the water jacket from the radiator until its up to temp, so its a pretty rapid process for the coolant. But the oil take a lot longer.

Why do I know/care so much about this? Well I have a couple antique vehicles that I run once in a while. Among the old car enthusiast community, its considered kind of gospel to never start a vehicle unless you intend to fully warm it up and run it for a while.

Seems to me that for folks like the OP, you are going to need to purposely put it in whatever mode causes the ICE to run the most and warm it up good and proper once in a while. Another poster described their process for this. I don't have my Prime yet to have any personal experience.

Finally, I tend to agree with a number of comments here and in other threads: there ought to be a setting where the ICE just plain was blocked from kicking on, or at least would throw nasty warnings that whatever you are asking the vehicle to do will soon result in ICE starting.....

Oil doesn't get to that temp. It usually heats up a hair after the coolant (5-10 minutes more in most cars, I've found), and hovers at 190-220(very spirited driving, almost a track event, if you have a properly engineered system and aren't in 100*f ambients is what it takes to break 220. I did it once or twice on the street in my 370Z, which has a known weak cooling system, and never even came close unless I was on the track in a Z06. Mine hovered 210 at the hottest on the street in 100*F weather when I was trying to have fun but not go to prison).

 

Not fulling charging, then sticking it in charge mode would keep the HV running for a while (and under load for more heat).

 

People love to freak out over fuel dilution...why?
Look at the wear data. It's fine.
Is it desirable? No. But neither is heating and cooling an engine. But you must, to operate it!
Look at the wear data, and use variation in fuel dilution to track problems (stuck injector, etc.). But to freak out over it for the simple sake of it existing does not seem rooted in real-world results, but rather, book-knowledge. Sometimes what's in the book must be set aside when the real world says "I do not care, this is the way it will actually be, regardless of what you "know" it to be."

 

People love to freak out over fuel dilution...why?

But to freak out over it for the simple sake of it existing does not seem rooted in real-world results, but rather, book-knowledge.

Increase in oil level can damage an engine. Decrease in viscosity isn't good either. MFG's spec these values and I want my vehicle in spec. Period. It's a concern but I don't see "freak out" here.

I'm not trying to bring book knowledge. I have well over 100 Blackstone reports for engines I work with over the last few years (mostly piston aircraft). I've seen multiple clean reports when there was visible metal in the oil filter / sump. I've seen spikes in wear metals in the analysis with no physical evidence. Oil analysis is a tool - ONE tool - in a toolbox to assess engine function. But it has given me something actionable here.

All I was bringing is a data point: My Prime that's mostly EV but short cycles ICE (for whatever reason) has diluted the oil to the threshold of viscosity and fuel % in 7k miles blended EV and ICE. In spite of extensive road trips that didn't boil a lot of it off. It's for other owners to decide if that data point, their observations, and their usage patterns warrant a more conservative oil change strategy. I've made my choice.

I completely agree with you that oil temp in cars doesn't range 300-400- Pure internet conjecture.

 

Regarding Oil temp. On my 2000 ford 350 diesel, I have both analog temps for oil and coolant. They are almost in lock step. The oil will get a few degrees higher under a heavy load, but not by much. 300* is not anywhere near real. My scangauge, on my RAV, has a digital read of coolant temp, and it usually is between 200 and 210 *F. Oil dilution is a problem for sure. The suggestions to run the ICE up to temp is the answer. Keep an eye on the oil level and adjust accordingly. FWIW

 

Is an oil temperature readout an option on the scangauge? Or just oil pressure?

 

I am not sure about oil pressure, but the temp is definitely there. There is a ton of info on the SG, some of it is way over my head.

 

My previous Subaru with a 2.0 twin turbo had an oil temp display, I also used a ScanGauge that had a water coolant temp readout. Typically the oil was no more than 15 degrees F hotter than the 190 degree engine coolant temp. I now have the upgraded software ScanGauge in my Prime. I usually display coolant temp, but have not been aware of an oil temp readout. What is the label for oil temp? When I tow my boat this summer, I would like to access this reading. I used a ScanGauge with a V-10 Ford that could display transmission temp, also a good thing to know when towing.
When I first installed my ScanGauge in the Prime I had a manifold air pressure (MAP) readout. That reading stopped displaying a number a few weeks ago, making me wonder if a sensor has gone bad.
I usually display RPM, Coolant temp, instantaneous fuel mileage, and either state of charge or trip fuel mileage. Occasionally I will check amount of fuel remaining (GAL), since it seems to be more informative than the gas gauge. It is surprising how quickly the engine temp drops when it is in EV and not running, at least in the cold weather since I got the Prime. And how quiet the engine is when not working hard and rpm's are below 2000.

 

Please disregard my statement (removed).

 

I take it you're not a chemical engineer LOL what a a statement!! Thanks for the laugh.

Is this not correct?

 

For sinbad. I didn't write it clearly. The temp I was referring to is coolant temp. I haven't seen an oil pressure or temp anywhere. Sorry for the confusion.

 

We do have transmission oil temp as an XGuage though. Thats about as close as we get. That’s the one I’d worry about, it cools the MG’s. Could be handy in towing.

 

Can't remember what the MAP was, but since there is no turbo, it will rarely be over 0, Mostly negative. It's a suvker, not a blower. 🍼

 

IIRC, it's Manifold Air Pressure, while a MAF will be Mass Air Flow.

 

Interesting data point. Singular. Without anything to compare it to, it really doesn’t mean anything. If a non-hybrid ICE shows .5 percent fuel in the oil it may mean something. Where does the less than 2 percent come from? Just a guess? Data showing that it causes damage? A half percent is not significant in my opinion. Could be measurement error. The statement “…likely thinned down the viscosity” is almost laughable. Do the test!

I find it interesting that there was no water. I would suspect that if the oil wasn’t getting hot enough to flash off the fuel then water would not flash off.

Even if all hybrids have a higher percentage of fuel than others it is not necessarily a bad thing. Certainly not a show stopper. It is just an artifact of the process. It does point to an area for improvement of fuel consumption.

To really understand if the dilution causes extra wear, the contents of the oil filter needs to be examined. But then comes the issue of comparison.

What did it mean: “Check back on fuel.” In the oil report?

 

Dont have my Prime Yet, but dont understand this discussion at all. What is ICE??

 

ICE = Internal Combustion Engine

 

Delete

 

So you are saying that using the engine for short stints like warming up the car in winter will cause problems in the fuel or in the oil ??? Why does one have to do with the other, they are separated systems.

 

they are not separate inside the combustion chamber. that is where oil and gas meet.

the issue is with some modes of operation and direct injection droplets of gasoline can get past the oil ring
on the pistons and down into the oil. this is the issue with direct injection

Toyota knows there will be some fuel dilution in any direct injection implementation and
they have thought ahead and the engine has advanced resin coated bearings among other
changes not seen in a port injection engine which essentially means do not worry about
it, this engine can handle a bit more percentage of gas in the oil with zero harm. 5% in
0-16 is about the limit where it's getting too much dilution. 5% and lower is not an issue,
it's been designed to handle it. proof are the many thousands of high mileage taxi hybrids that
do not need, and have never had, the engine torn apart to fix anything.

 

Thanks Noelin, so if I am going to warm up the car ensure at least 8-10 minutes of use prior to switching! Makes sense. If just going to the corner store then bundle up and forget about ICE LOL>

 

Sure, for all SHORT trips like that, EV all the way. Almost always for our local use we have no problem getting to destination and back on EV so that's what we do. If, for example, we have a use which will exceed EV range, we will switch to HV about 8 or 10 minutes out from home. With a starting ambient temp of say 38F, I've clocked how long it takes for COOLANT to reach maximum temp, and it's about 6 minutes, so will give it another couple minutes to help vaporize moisture further. This is different in summertime here so the warm up time is much less. For our use, it's rare to have to use HV mode for day use trips. In this scenario we make a point of using HV every 10d or so just to use up fuel. Also, when super cold out we will use HV mode and get the benefit of the warm ICE to help with keeping the cabin warm. We fill to about 1/3 full and use it up not longer than 2-3 months tops. On trips, it's a non issue as it's HV all the way.

 

Much thanks for the practical advice.