It so happens that my wife took our 2019 Rav4 hybrid on a trip this weekend so I checked the fluids before she left and noticed that the oil level was above the higher mark which surprised me since we had our last oil change about 7,000 miles ago. I didn't check it after the last change, so I don't know if it went up. We've had all oil changes done at the dealer.

I will get an oil change soon, then monitor closely. How did you go about getting the oil analysis? Theoretical question: What if I had mine tested and got the same result? Our vehicle runs perfectly. Just continue to monitor?

I am also a past Prius owner. My 2010 Prius eventually began to use oil, never had the level go up.

 

I will get an oil change soon, then monitor closely. How did you go about getting the oil analysis? Theoretical question: What if I had mine tested and got the same result? Our vehicle runs perfectly. Just continue to monitor?

I would recommend running shorter oil change intervals if you have a fuel dilution issue. Over 5% is pretty significant.
What is Fuel Dilution (and Why is it Bad)? – AMSOIL Blog (attached image if from this link)

If I had a vehicle that had more than 3% fuel dilution I would buy the cheapest 0w-16 or 0w-20 synthetic oil I can get and run shorter oil change intervals. How short? Depends on how bad the fuel dilution is, no more than 5k with fuel dilution over 2.5 or 3% (for me). Mobil always has promotions where you can get a 5qt jug of mobil 1 for $15 or less after rebate.
There are multiple labs, I'm not up to date on which is best and such. (blackstone, polaris, wearcheck, caterpillar, etc) Just make sure whoever you choose, or the test package you choose includes fuel dilution.
oil analyzers inc

https://www.oaitesting.com/services.aspx

 

I love it. A thread on oil & oil filter changing intervals that prima facia demonstrates the potential issues for putting 10,000 miles on the lubrication system of an ICE that sports an oil filter the size of a sewing thimble.

 

I'm not about to get an analysis. I figure it is unlikely to be an isolated issue. It will either show up commonly or it won't. I will get an oil change, monitor and go from there.

 

My current plan is to change the oil and filter at a 2500 mile range and have it tested at the same time just to see where it is. Since it‘s used for mostly short trips during the week, I may have to change oil and filter at the 2500 mile range going forward. Whenever I took it to the dealer to do the oil changes, they always overfilled it by putting in 5 quarts of their oil and it always read over the full mark on the dipstick. I would usually just go ahead and change oil and filter at the 5000 mile range to get it back to right on the full mark. I always hated overfilling with oil as that isn’t good either. Wife will tell when the engine is starting to get slightly louder and that is a good indication of needing the oil changed. This oil change above where it was tested had a little over 4900 miles. Since it’s a hybrid and there are probably some people who only are doing short trips, they may have the same issue and not know it. After I get the oil analyzed the second time, it will be a visit with the Toyota dealer and service manager to get this on record. Increased wear of the engine and a shorter engine life are not what I had hoped for with this vehicle. Thanks for all the reply’s.

 

Fuel dilution has become a common problem with many of the newer engines with direct injection and auto start/stop. It was a very rare problem in the past so it's an unintended consequence of federally mandated CAFE standards. What good is saving a few mpg if people are changing their oil twice as often?

 

I have not noted a rising oil level on mine but I’m planning on doing a UOA on mine just in case.


I found another A25A-FXS engine owner with fuel dilution issues.

M1 AFE 0W16, 5178 mi OCI, 2021 Toyota Sienna Hybrid A25A-FXS

Hi Everyone, Got a report back from my very first UOA. Had heard of Blackstone services a long time ago and now finally have a reason to use them. Obviously the crankcase dilution is concerning but after doing a lot of reading on this forum and elsewhere on the internet it appears a long...

bobistheoilguy.com

 

All that high moly 0w-16 does no good with fuel just wash it off. Do you take a lot of short trips? Yet another reason I’ll continue 5k intervals.

 

Interesting item I’ve found about fuel dilution.

Solving Gasoline Direct Injection Issues: The facts and fictions of GDI - Engine Builder Magazine

Learn about the challenges and solutions related to Gasoline Direct Injection (GDI) in engines. Issues, design flaws, and potential fixes.

www.enginebuildermag.com

 

Toyotas engine also has port injection in addition to direct injection. It’ll switch between the two depending on driving conditions. Mazdas don’t seem to have much issue either with fuel dilution and being only direct injection. I’ve never had oil consumption or oil level rise on my ‘13 CX-. The issue here is short trips as the OP has guessed : (

 

It's a problem with Mazda's as well as it's a common problem across all GDI engines. Short trips will result in fuel dilution with GDI engines.

Mazda's official stance on the matter: https://static.nhtsa.gov/odi/tsbs/2018/MC-10142533-9999.pdf

"If a vehicle is driven on extremely short trips most of the time (where the engine never reaches normal operating temperature), the engine oil may become diluted with fuel and the engine oil level will increase. Engine oil dilution with fuel occurring under this specific driving condition is normal with direct injection engines."

 

When I had a 2020 Rav4 hybrid here in Australia I too also noticed oil dilution. The oil level did go up a little bit at the 5000km mark so I changed the oil anyway. So yes I think there is a oil dilution issue with shorts trips maybe?

 

One reason for coming here and posting the oil analysis was I was hoping to at least show some who may not be watching their oil level, doing short trips and having fuel dilution with putting 10k miles on the oil and filter. Results could bad later on!

 

Thanks for posting your analysis. It backs up the whole “stick to 5K intervals, oil changes are cheap” mentality that so many of us have adopted.

 

Thanks for postping over on bobisgtheoil guy. Brings light to-fuel dilution with these engines.

 

Finally got around to getting another sample done. This time we had used the Rav4 for a couple of longer trips. This sample was taken at 3100 miles. Still shows fuel dilution, yet not as severe as it was at 5000 miles. I’m figuring when the temps get colder, there will be more dilution as it will not be driven much except for short trips.

 

Interesting this is happening to some Hybrids too. Ugh. Note that Oil Analyzers tests for fuel dilution using "GC" which stands for gas chromatography. Its better, especially in very light oils (like ours). Blackstone does not.

I am contemplating switching to 0w-20 and keeping 5000k miles OCI and forgetting about it. Its cheaper than sending $30 oil samples. Probably will only change the filter every 2nd or 3rd oil change, as you can see the oil is PRISTINE except for the gasoline in it....

 

in 2032 10 years after my 2022 I'll do a compression test and show you that it is fine
someone just wake me up

ignoring all this fear of fuel dilution.

spend money just to have oil analysis done, and returned to me so I can do exactly what with that information again ?
I don't build industrial motors or race motors. I drive a rav4 with a warranty and operate and maintain it according
to the manuals....if it blows up, jams up, dies unexpectedly Toyota will fix it. thing is, Toyota hybrids are not croaking
left and right due to fuel dilution. but those oil analysis documents boy oh boy they put the fear into you. not me

 

I have seen plenty of "fuel delusion" issues on the forum (people believing MPG is what the car says at any given time) but no dilution issues yet.

 

Im doing the first oil change today at 5k and some change. Sending sample to blackstone tomorrow, so curious as to how ours is holding up.

 

Please post your results if you can. If you use it for short trips, it will probably show some fuel dilution. Hope yours is ok!

 

Just read through this entire thread and it seems that the underlying common theme is "short trips". HOW short? And is it only with the Direct Injection vehicles?

I have never noticed increasing oil levels (a symptom of dilution), but who is to say that the engine uses just a bit of oil and dilution is keeping the level good, leading me to believe I have no problem?

Regarding "short trips", my wife (the RAV driver in the family) does about 7 miles of suburban driving to get to work. Hers is an older RAV ('02) with port injection only. A couple times a month, she might go to our son's house (1/2 hour drive) or her sister's house (50-minute drive). My commute (in an '18 Sienna with port and direct injection) is about 10 miles, which includes about 4 miles of freeway driving. My job has me driving to locations to service equipment several times a week. Those trips range from about 3 miles to about an hour away. My van is our go-to weekend vehicle, so it sees more trips of the longer variety. Does either of these scenarios qualify for the "short trip"?

.

 

I consider everything below 30 miles as short.

 

really ...what damage from fuel dilution ? please, some hard facts

d4s uses resin coated bearings which are super low friction, and easily accommodates
0-16 with whatever fuel dilution. these bearings are not your normal engine bearings.
does your oil lab test for resin particles which is what really determines wear on critical
bearings ?

 

Short trips are those that don’t allow the engine to reach and run at an operating temperature sufficient to burn off gasoline that is finding its way into the oil. There is no set mileage as it involves a number of factors. How long is the engine idling? How cold is it outside? Did you start the car, go a couple of miles, and then stop it before the engine really warmed up?

 

Bottom line, the engine oil needs to get up to a temperature high enough and long enough to vaporize any fuel that gets into the oil so it can vent through the PCV valve and get burned off. No matter how hard you try, the metal rings of a piston can only seal off so well. Direct injection can increase the passage of fuel and if you have a turbo to the mix with direct injection, that just adds additional pressure in the cylinder. Thankfully, we have both port and direct injection but no turbo pressure.

Yes, outside temperature can effect the time frame since the oil in located in a metal tub exposed to the elements. The shrouding under the vehicle can reduce direct snow and ice contact but metal outside will get and remain cold a long time.

 

I too have the oil dilution problem. It is ridiculous to expect owners to take long highway drives to address a design problem with the engine. I can accept the 5K OCI, but the rest is ridiculous. The car is here to serve our needs and not the other way around. I'm sure engineers at Toyota never have the final say. Some guy in the marketing team and PM group are making all these wrong engine design decisions.

 

If the engine is controlled by the EU "computer" according to programming not by the driver directly
wouldn't the design take the hybrid function itself into account.

First time driving a hybrid, was quite surprised after finding out I was unable to start the engine directly nor had any control over when it did or when it shut down except for shutting down / turning the vehicle off

 

If the engine is controlled by the EU "computer" according to programming not by the driver directly
wouldn't the design take the hybrid function itself into account.

First time driving a hybrid, was quite surprised after finding out I was unable to start the engine directly nor had any control over when it did or when it shut down except for shutting down / turning the vehicle off

The ECU controls everything from valve timing to injector pulse timing and length and which injector to use. If I could examine the ECU code and the number of sensor inputs and outputs, I'd quickly realize I am not smart enough or quick enough to react as well or as quickly. Compute air density, gas octane, combustion byproducts, accelerator position at least 10 times a second and output control settings to at least a dozen pieces of hardware. Been this way for at least 20 years on all makes. Not just Toyota and not just hybrids.

 

FYI. This is my 2nd rav4 hybrid. This current my23 model too shows oil or fuel dilution issue. Ohh well more regular oil changes I guess.
I've been doing a lot of shorter trips and in colder weather which would probably increase it.

 

FYI. This is my 2nd rav4 hybrid. This current my23 model too shows oil or fuel dilution issue. Ohh well more regular oil changes I guess.
I've been doing a lot of shorter trips and in colder weather which would probably increase it.

You have it! Toyota has a problem with these engines and has not acknowledged it yet. It will come to light and they will have to pony up at some point. Hyundai and Kia did.