Trails and Tribulations - Oil consumption and catching oil

Been a forum user for almost a decade now(mostly reader). I always found answers I was looking for here.

Our 2006 Toyota Prius crossed 120k without much trouble. But I started observing some oil consumption I would say after 100k. Not too much, basically, my guess is 1/2 quart to 3/4 quarts between oil changes (5k OCI).

I always fill 1/4" inch below Top line of dipstick, and worst I ever observed - Oil was about 3/8" inch above low mark. So whatever quantity it takes to fill from 3/8" low mark to 1/4" below high mark is what is consumed between oil changes (5k OCI, about 5months to 6months between changes).

Little Bit of History:
I have been pampering or may be I should say took care of it well all these years. First 3 years(30k miles), its the dealer maintenance. After that I started going to independent who use Semi-Synth oil. After losing confidence in shops(at times I see, school kids looking to find drain plug, or battery etc).

So, at around 50k I took over maintenance my self and only used Synthetic, started Penzzoil Ultra 5-30 until it was available, later switched to their Platinum, then finally to Mobile 1 for last 30k or so. Usual change of Air Filters, Cabin Filters, in between Water pump/Extended Warranty, Coolant pump/recall, belts etc.

At 60k, I did replace PCV valve despite looked dry and working good, changed transmission fluid. At 110k as maintenance calls it, I replaced with Denso Iridium plugs. Old Plugs were really looking good.

But the oil consumption has been bothering me, when I looked at PCV valve, it is little wet with oil. So, I changed oil to Mobile 1 5-30 High mileage oil with assumption that HM oils are less prone get burned. Ran thru 6 cans of Chevron Fuel system cleaner as someone suggested that it fixed problem for them.

After changing oil to HM, after few thousand miles I checked intake manifold, I see oil in the intake manifold. Not sure if this is because this HM oil is not getting burned. Also observed PCV valve is pretty wet with oil though it is not coked or anything like that. So, I took plugs out and see oil film on the new plugs.

Next oil change, I did ran Lubegard Synthetic engine flush 95030

as this is supposed to be gentle synthetic formula compared to their cheaper/regular formula. Oil was tiny bit darker and less viscous, but not drastic difference like some of those dirty engine oil changes. Looks like engine is pretty clean. I only ran for 15min in Idle.

Replaced oil (Mobile 1 HM)and filter, replaced PCV valve and started observing . After 200 miles, not much change in oil level, but I still see oil in the manifold, plugs coated with oil. Also what I observed is when I take out the Oil fill cap, I see air coming out with pumping kind of action with slight pressure(not enough to move the cap though). When I compared to my only other ICE vehicle, 2015 Honda Odyssey, Honda does not have gases/pulsing in the oil fill hole. Ofcourse it only has 16k+ miles vs 120k miles, but I was not expecting that kind of blowby(I am not certain it is blowby either) on well cared Toyota Prius.

So, I was searching forums, and I see some suggested that oil consumption may be because of oil control ring coking and suggested piston soak. I removed plugs and inspected first with boroscope camera and Pistons are surprisingly clean. Other than slight brown stain spots on the side, no carbon, no coking, nothing. Nevertheless I soaked the pistons overnight with seefoam and sucked out excess remainder seefoam next morning. (see pictures).

Since some seefoam seeped into oil anyways, I ran the engine on idle for 10 mins and replaced with new Mobil 1HM oil and new filter. This time I added Motor Silk additive which I have been thinking for a while. This is a lubricity enhancer+good cleaner.

Put everything back, but this time, I added Air compressor oil/water separator between PCV valve and intake. In 200 miles, I see about may be 15-20ml (probably around half-an ounce) in the the Oil separator. Now, I see intake manifold is completely dry. This further confirms oil is coming from PCV and making it into combustion chamber. But not enough to cause/trip any DTC, or any smoke at the tail pipe. But I felt (not certain) that oil in the separator (think of oil catch can) smelled some gasoline in it.

BTW, I also did brake work at this time, replace front pads and rotors and caliper on the front driver side as I saw inner brake pad only on last 2mm. I have been checking outside and that is more like 4-5mm. But it seems inner pad is wearing more(heard its pretty common). May be because grease dried out for pads guides and caliper guide/slide pins. Did usual brake fluid flush.

Overall after this work, I did see 7-8% improvement in fuel economy in this round. Not sure if this is purely attributed to Motor silk or not. Nevertheless it felt engine starting is little smoother, and car felt tiny bit peppier. But again, it is not driven by me on regular basis as its my wife's car and she does not know anything about car or what I did to the car. Only thing she may notice is, if the steering wheel is missing. . I am not kidding, she does not even look at dash indicators, but I keep checking things on the car once or twice a month to make sure. So mileage gain (despite weather getting colder, usually when mileage drops) is for sure, and I think some credit goes to Motor silk I think.

Anyways, my concern is not mileage. Since I am seeing oil in the catch can, I removed plugs and checked, and this time plugs are dry and looking good. So finally I installed Toyota Techstream and connected to car. No codes on any modules other than TPMS( battery dead 3 censors).

So, I loaned a compression test kit from local Autozone, and ran compression test using Toyota Techstream. This kit was lousy kit where you twist the hose in the spark plug hole, and connect the gauge. The gauge check valve itself is leaking, and not holding air well. Nevertheless I ran the test so that atleast I would know relative values.
Surprisingly all gave 110psi, except cylinder 4 gave 112psi. So I consider that all are pretty much same. I ran wet test on just one cylinder because all are showing same values, and wet test put it at 130psi. Obviously some wear is expected here, but not sure raise of 20psi between wet and dry test is normal or not. What do you folks think? Is it normal for wet test to raise 20psi?

Yes, as per Toyota spec that much consumption is normal (basically Half-a-quart for 5k miles approx), but it bothers me that it is coating plugs and going into intake. I am pretty sure it also causes intake valve getting all the crud in the longterm in addition to reducing efficiency because of two factors. Ofcourse oil catch can(I mean water/oil separator) I put in between doing pretty good job, but this is of pretty small capacity( I had to close drain valve as in this case we have vacuum unlike compressor air).
So, I got a cheap Oil catch can from amazon, made good mount and connected it. But it turns out these so called oil catch cans they sell are useless. It literally did nothing other than can became little bit wet. This also introduced oil in the manifold again.

So, I reverted back to Air compressor oil/water separator again. But this I need to check/drain every time gas is filled as this can't really take more than an ounce of oil and I do not drive this car. This is a messy affair too.

But I want to address the root cause if possible. Any suggestions, alternatives to address the root cause?

BTW, I do not want to use "Engine Restorer" or something like that. That is a last resort...if nothing else improve things.

 

Hi Bisco,

Thanks for encouraging words! Any words of wisdom?

Thanks

 

I didn't realize that is 1.5 quart between marks because I never did fill-up between oil changes. I am very cautious about overfilling, and making sure oil is always above low mark. Even during oil changes, I always fill new filter with oil to the brim and install it so that there would not be any dry starts. That's why it is feels painful to have oil consumption like this.

Yes, tried overnight piston soak with See-foam. Didn't see any difference. Piston are not loaded with carbon or anything like that, but don't know how the rings condition. I am kind of cautious to run the engine with any strong solvents.

May be next I will do little short OCI and use BG 109 Engine flush during the oil change. Read good things about it.

BTW, I started Star Tron Ring clean+ additive to gas in the last tank. Only need 1- 1 1/2 ounces for each tank, so I will probably run next 8-10 fill up with that and see if this makes any difference.

 

Sorry for not providing further updates in a while.

I ran BG EPR (hybrid version) which I got from local distributor before the oil change. It did seems to clean up rings somewhat. As the distributor recommended, (hotter the engine better the cleaning) I poured BG EPR in hot engine, ran for about 30 mins before draining the oil.

Now, after 5000 miles, there is some oil consumption, may be half quart. Haven't seen any misfires. Also, I removed the Oil Separator as it is not taking the heat well in the engine compartment and hot gases. Its disintegrating. So have been running without it since last oil change.

I initially checked intake manifold for any oil, it was dry. But now after 5000 miles, I do see some oil in the intake manifold. I am going to do one more run of BG EPR again for this oil change and observe how much further improvement is there. There is definitely improvement first time, but I am hoping for even better results. It seems to point to carbon on the rings. Though engine has only 130k, has been maintained very well, most of the driving is short runs, local driving. There are few long drives with full loads and high throttle, but those are far and few.

So, that might be one contributing factor for ring land carbon.

Also, want to update on Hybrid Battery. I got usual red triangle error and I can see even after few resets it is coming back. I saw that Hybrid is battery is discharging very fast. I observed the Battery modules charge level using OBD Bluetooth Dongle as well as TechStream and I found the problematic cell.

Later got couple of used good cells from ebay for $60 buck, I replaced the bad cell with one of the cells which was closest match in that pair of module. Its been 4k miles ago, and has been working well without any issues. Hopefully it works until we retire this car.

Finger crossed on both of these accounts.

 

I was not the owner for the first 30k miles, but first owner has all records of all changes at dealer and done at every 5k. I know it did not use any oil even at 90k at all. So it was not a problem with oil changes as it was changed frequent enough. So, I don't think issue is anything with oil quality or the frequency. I think main issue might be our driving cycle.

Of course many are oblivious to the fact that engine is consuming oil. I did not need to add oil between the oil changes, but that does not mean oil is not landing in the intake. Recent consumption is, my oil level went from 2/3rd to 1/3 on the dipstick between high and low levels. There are no errors or anything like that. You might have seen above pictures, the pistons are pretty clean.

Many cold starts and short drive cycles does impact the deposits. (Probably my 130k equivalent to 200k+ regular/highway driving cycles).

There is no mileage drop, no errors, but I do check and care about the vehicle to keep it in the best shape possible.

Yes, I do pamper the vehicle, even brakes, I replaced front rotors instead of resurfacing, even replaced caliper set instead of simply replace pads and be done with like many do(including flushing brake fluid). Even Tire rotations I do myself, Torque with Torque wrench as I have seen incorrectly torqued lug nuts.