I think I've figured out why there's oil burning in Prius

Yes, this exactly. No matter what speed the engine starts at, the ICE load is not necessarily large. It can be large however if the battery SOC is low and you require significant power (hill climbing or acceleration) before the engine warms up. You can sometimes hear it fairly clearly at start up when you're accelerating and the engine revs suddenly jump from very low speed to quite a high speed because it doesn't have the electrical grunt to provide the power you're demanding.

My best advice is to keep the power demand as low as possible for the first minute or two. And if you do need even moderately high power demand in the first minute then just let the engine idle to warm up for about 40 to 60 seconds before you drive. Ideally you want to get it to the point where it's warm enough to allow the engine to cut in and out before you demand any significant power.

Yep, I do this too and it definitely helps. I've been advising anyone who'll listen to do this for some time now.

 

My 2005 with 231,700 Miles hardly burns any oil. Maybe half a court every 3500 miles. The same amount as my sisters prius with 162,000 miles

 

Depends on the day. Mostly I drive away as soon as I power up. But my gravel drive way is almost half a mile long, so it basically idles all that way, most the time not even charging the battery.

 

With my 3 mile commute I don't get much time to replenish the ev battery. I find I get more consistent mpgs on this short trip by letting it warm up and go into ev, which takes less than a minute. I use cruise every chance I can to prevent myself from forcing ev. Half my trip is 35mph and the other half 45mpg with a few stops. I only force ev (stealth) when coasting for an eventual stop. My theory is that if I drive right away I will most likely only have half the ev battery available and this initial usage, by not warming up first, will deplete the ev charge until ev mode is not available. The rest of the trip is spent trying to replenish the ev battery, which really drags down the mpgs.

* When referencing ev I don't mean the button, I mean when the vehicles goes into ev mode.

 

How much oil are we talking about? One quart per 5000 miles, or more?

My Prius engine seems to run at fairly low rpm most of the time unless I pin the throttle. Even then, I can't imagine it's going above 5krpm.

I once owned a Honda with a KZ320A motor that redlined at 8600 rpm. It was common for that engine to burn about a quart every 2000-3000 miles, especially if you drove it in a spirited fashion regularly.

 

I drove the piss out of my 04 Acccord K24 Manual. I would burn a full quart every 5k oil change. Bought it in 07 with 108k. Don't know if the oil consumption was age, driving style or common for that engine...or all of the above.

 

The Gen2 redlines at 5k and the Gen3 at 5.2k (only number I found).

 

I just realized I mistyped the engine designation. It should have been K20Z3. In any case, Honda makes some real screamers. That engine generated about 100 HP per liter - normally aspirated from the factory. I had it bumped up to about 260 HP out of a 2 liter - NA.

I think that kind of oil consumption is not considered unusual for those engines.

 

honda makes some serious engines.

 

Im not sure of the cause since the gas engine runs much less then a normal engine the oil consumption should be much less....
Lets say you burn a quart in 1000 miles its really burning a quart in about 600 miles and that's not normal for any motor..
I saw some people posting that their cars have under 150,000 miles showing so the motor might have 90,000 miles on it and burning a quart..
I was looking around on other Toyota web boards and cars with the same 1.5 motor do not have a failure rate like this.
In my case my 04 lost one and a half quarts on its last 3000 mile oil change, Im guessing the motor ran for under 2000 miles of the 3000..
very disappointing but still cheaper to run then my work van

 

Most of these people do a lot of freeway/highway miles, so the the engine would probably be turning a lot more than the 60% that you estimate, probably more like 95% of the miles for many people.

BTW. The engine is always turning at any time you're going more than 42 MPH, regardless of what the display may appear to indicate.

 

There are always those odd ball engines that consume more oil than its peers. My guess is the random variation in the machining process of the cylinders, piston rings and valve stem seals. You may consider trying a thicker oil weight like 0w-40 where you have good protection at cold start but thicker at operating temp. Your gas mileage may decrease though.

 

If oil consumption is caused by piston ring and/or cylinder bores and/or blocked oil return holes thicker oil may actually increase oil consumption.

So if your engine didn’t use (a lot) of oil when it was new and now it does I would start by cleaning cylinders: Oil Consumption | Page 4 | PriusChat change oil after that. If that didn’t help then maybe problem is with valve stem seals. Bad valve stem seals normally make engine smoke at first startup but with Prius starting system that may not show.

 

The engine isn't dry, it's merely not burning fuel. The MG1 and MG2 spin the ICE at all times. The oil pump is operational from the moment the motors start to spin.

 

Just adding something to the thread, there was a member here that (IIRC) rebuilt their high-mileage Prius engine themselves. I cant remember the exact mileage, but 150,000+ comes to mind when they tore into the engine, they said everything looked - and micro-metered out well - except for the piston ring drain holes, which were plugged with carbon, thus leading to oil consumption.

 

One more reason to test cleaning with solvent. You can even just use diesel for this. I have seen it work on older Toyota engines. And it has worked for Prius as well Oil Consumption | Page 4 | PriusChat

 

My experience was with the onset of sudden oil consumption in a 2010 Prius. IIRC, 2010 was the year that Toyota shifted to synthetic oil and extended the oil change period to 10K miles. I had free oil changes with the dealer for the first two years. At no time during the scheduled oil changes was the oil down significantly during the recommended 10K period. However something drastic happened between 70K and 80K. I had checked the oil about half way through and it appeared fine, but at the 80K change the dealer informed me that I was down more than a quart. I was worried, and so I checked the oil at each gas stop on a 1700 mile trip that followed. Over the course of the trip, I had to add 1.5 quarts of oil. When I arrived at our destination, I took the car to the local dealer. The dealer said I had a small oil leak but not enough to account for that much oil loss. I was a little upset that my own dealer had missed the leak. I suspected the big oil loss was the result of rings that had gone bad. The dealer told me that I would have to guarantee $2000 in dis-assembly charges to check the rings. Not only was I within the 5 year engine train warranty, I also have a 125K, 7 year extended warranty from Toyota (cost $2000 at closing). The warranty did repair the oil leak, and I only paid the deductible for what would have been an $1800 bill. But the dealer said that Toyota would not open the engine to check the rings under warranty unless they ran an oil consumption test. For that test, they topped off the oil and I would drive for 1200 miles. If the engine did not use 1.2 quarts of oil, it was considered to be within factory specs. That's an average of 1 qt of oil per 1000 miles.Who in their right mind would buy a car in which that was considered to be within factory specs? When I got home. I had the dealership run the oil consumption test. The result was about 0.9 quarts of oil over 1200 miles. Toyota said that was within specs, and the car could not be serviced under my extended warranty. Since then, I've added about a quart of oil every 1500 to 1800 miles. My gas mileage dropped from about 47 miles per gallon to about 37 miles per gallon. My theory is that Toyota used rings designed for 5000 mile standard oil, but then switched to 10000 mile synthetic in order to increase gas mileage. (See lawsuits over other Toyota models for massive losses of oil that Toyota refused to fix -- until recently. Prius is not included in that 2015 "goodwill gesture" for other Toyota models). I still have time left on my extended warranty and so I've kept the car in the hopes that Toyota will repent of its usual tactics when something is found wrong with a car. I have hopes that Prius will be included in a class action which I will gladly join. As for myself, I recently bought another hybrid, a CMax from Ford. I never considered another Prius during my search for a car. Is the CMax better designed and more reliable? I don't know, but so far I like it better than the Prius. In any case, I don't plan to ever buy another Toyota product, and I will recommend against it to anyone who will listen.