My theory on why some Gen 2s consume more oil after 150k miles

I actually did say:

So, we are in a partial agreement. I say partial, as there was a PC member who fixed his oil thirsty prius engine and reported back that each piston has 8 oil holes, unlike the notorious oil burner early 1ZZ-FE engine that was fitted with only 4. Furthermore, the holes were not obviously plugged even though the pistons were dirty.





Credit: 2008 Prius - burning oil at 135,000 miles | Page 5 | PriusChat

 

I researched the issue a bit more and you deserve the credit on the non-ethanol gas angle. Now that I think about it, there were a few studies that did show more piston/rings deposits with E15 and E20. Not sure of E10. One of the best studies was the Australian government sponsored E20 study done by the Orbital Engine Company in 2003 (IIRC). I downloaded it many years ago, but it's not available online anymore. There is a reference to it here:

TR Register

Based on the study, Australia scrapped the E20 idea, as E20 produced a slew of problems after long term use, especially in older cars. Those problems would not surface at the short term use. However, maybe with long term use even E10 has similar effects.

Now, the point is mute as E0 is practically not available in USA anymore.

The best we can do to mitigate the piston deposits from ethanol use is to use best oils (Dexos standard has the best piston deposit protection), cut the official Toyota OCI (probably tested with E0), and maybe even start doing the old fashioned oil flushes with oil changes.

 

E85 is totally off topic, but since you mentioned, E85 is not that clear burning as some people paint it. Maybe this is why E85 use is considered severe service and short OCIs required? It can produce bad deposits:
NASIOC - View Single Post - E85 Injector Build-up / Gunk
NASIOC - View Single Post - E85 Injector Build-up / Gunk

As for the E10, we don't know. We do know that E15 and E20 produce more piston deposits. That have been studied and published.

And finely, let me make the point that oil consumption via rings is a multifactorial process. You have to have a number of factors for that to happen. They include oil viscosity/oil film thickness, oil oxidation resistance, OCI, piston temp, high RPMs, high vacuum on intake stroke, piston/oil ring deposits, ring and/or liner wear, ring construction/tension, etc.

 

Here's another possible theory as why some Prius engines could experience somewhat higher levels of carbon build up.

My other car is a 2005 Mazda 2 (I think they call it "Mazda Demio" in some countries). It has a similar sized engine to the Prius and a slightly larger (4L) oil capacity. I do my own oil changes in both, and I always take each for a short drive to warm the oil before changing.

One thing I've noticed is that, for the same short warm up drive (same route and speed), the Mazda oil gets way hotter than that of the Prius! TBH I estimate that I'd need to drive the Prius at least twice the distance (maybe more) to warm the oil to same degree as the Mazda does. (This is just a casual drive on local roads btw, I don't have a nearby freeway.)

IMHO this could be a definite factor for some people, especially people who do a lot of short distance or low speed trips.

 

By how badly it burns my bare skin when I unscrew the drain plug and some of the oil invariably drains across my hands and wrist. That and also by how many times I say "ouch" while unscrewing the oil filter. Yes seriously.

For this reason I actually try not to overly warm the oil, just enough really to get a good fast drain. However when I take the Mazda on the same route that works for the Prius it always comes back with the oil way hotter - and much more "burny" on my poor little hands.

 

Jadziasman,

I can't comment on an E-85 flex fuel vehicle that has been driven 367,356 miles only on a 2006 Toyota Prius that has been. And the data from Ema says E0 makes a HUGE difference in her oil consumption.

By the way she passed emissions this morning so I will be able to keep feeding her oil and note any further improvement or not over the next 40,000 - 50,000 miles I put on in a year.

Happy driving,
Chris

 

Double Post removed. PriusChat issue?

 

WOW, another bug-a-boo about ethanol: It makes your engine use more oil.

I'd like to hear more about that please.
I am highly skeptical.......like NO WAY.
I think there likely is a flaw in your method somewhere.

 

Well, my old (1993) Toyota Corolla DX Wagon started burning oil at about 150k miles, and when I asked my friend Erik (from Estonia) about it, his first question was "So, how fast do you drive?" to which I replied "…usually around 85 or so…", "…well, says Erik "…try keeping the speed down, and go easy on the right-foot!" …so, I followed his good advice - no oil burned between changes (~4000 miles, oil & filter change, ever since the car was new), and 142k miles later I traded it in for a 2009 Gen II Prius, (reason I had to get rid of the Corolla was rotten sills (buggeration!) (see threads passim). BTW, after I learned to lighten my right hoof, I switched to Castrol GTX High-Mileage and never looked back! (…so can't say I ever really noticed the blue smoke! )

 

ROFL, really? Here is the method ... I measure the oil with the dipstick after an oil change and see that it is up to the upper dimple. I set the "Engine Oil" miles under Info in the Maintenance Screen, very useful for other things as well by the way, for 1,500 miles. I check my oil every couple of fillups or when the screen says my 1,500 miles have be driven. I pour 1 quart of oil into the engine to bring the oil back up to the upper dimple after said 1,500 miles.

As a mechancial engineer with 20 years experience in field service please let me know what I am doing wrong here, lol.

Happy driving,
Chris

 

Jadziasman,

Sorry to hear that there aren't any E0 stations in your area. I'm really surprised how many there are in NC and TN. Although my runs to KY and OH have caused me to use E10 a few times. Most of the E0 stations I find I have to take my license in to have them turn the pump on, then pump then go pay. A few have pay at the pump but not many.

I use an app called Pure Gas to find E0 stations from my iPhone. The website I think is www.pure-gas.org but I think there are other websites and apps out there. I looked for District 6 stations but your right there aren't any near you.

Happy driving,
Chris

 

Interestingly, my 2004 prius with 250000 miles at the time was using 1qt./1500 miles until I did several 2000 mile trips at high speed (75-80). Which caused a reduction of oil consumption to 1qt/3000 miles. After those trips the oil consumption has gradulely gone back to 1qt./1500 miles as I have reached 310,000 miles. My theory is that the high rpm over a long period of time wore off the shelack that had built up on the cyclinder walls over time. Notice also that my normal day is a 92 mile comute up and down lite hills (between 2 to 3000ft alt.). At 250,000 miles I also started using better quality gas from Shell, Chevron instead of discount stores. So forget that theory. Also I use full synthetic and change every 10000 miles (since it was new) until recently, usually around 13Km between oil fillups.

 

Interesting. My experience with corolla (with deficient piston oil holes) was the opposite. No consumption until I did a high speed hwy run (>80 mph) in very hot weather with AC and increased load. After that event, the consumption stayed for a while (1qt/2000 miles) until I did some piston soaks.

Not sure what you mean about forget about better gas theory. You had consumption with cheap gas prior to 250,000 and then you started using brand gas. How do know it wasn't gas?

BTW, there is no such a thing as "shelack on the cyclinder walls." There are piston deposits though. The carbon deposits on piston domes get better with hot pistons, but the ring deposits get worse.

 

I agree with this, especially with respect to European vehicles. My Volvo 850 used about a qt every 3500 miles when new and uses about the same amount at 260,000K miles? The Volvo's piston design isn't anything special -- just a generic Mahle design from the era. My Audi A6 was such a leaker that I could never get a trend on actual oil usage.

The Prius, actually most Toyotas, are different in that they use virtually no oil when new and may or may not see increased oil usage when older. Zero oil use may be what customers expect and perhaps Toyota designs accordingly? The only issue is that owners may get accustomed to zero oil use and may fail to check oil frequently enough to detect increased usage.

 

For pity sake. (Cleaned up for public consumption.)

As a Mechanical Engineer, you should KNOW that is NOT the part of your methodology that I am questioning.

What I am questioning is how exactly you were able to objectively keep all of the other possible factors the same during your test interval so that it is impossible or highly unlikely that some other factor accounted for the difference in oil usage instead of or in addition to the ethanol.

Or to put it more simply, how did you KNOW with scientific certainty that the ethanol was the determining factor.

Since seemingly nobody else in the whole world has come up with similar results, I remain highly skeptical of your conclusion.