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

Hmm, my wife and I both own since new a 2005 and a 2006 Prius. Each of us drive to work and back and live ordinary lives and have jobs we can't wait to retire from. We live in a state that has ethanol in the fuel. That said, we are not different them the average Prius driver. We put on about 15,000 miles a year on our cars and we always drain and refill the oil every 5000 miles and use Toyota filters. I know because I do all oil changes. I have used only synthetic since new on both cars. Her car burns no oil with higher miles. Mine well, it burns 1 quart every 1500 miles. Whats the difference? My wife drives like a 90 year old lady... she never stomps the go pedal and never revs the motor. Me... I'm an old SCCA racer so, I drove it like I stole it. It's been that way since day one. I have no tickets, neither does she, the difference is I deserve some I never got.
There is another factor in why some Prius burn oil and others don't. Driving style. I mash my foot to the floor at least 10 times in a daily commute. She never would even consider it. It's no wonder, given how I drive, that it doesn't burn more oil or throw a rod. The prius is still requires less work on it to drive, then any car I have ever driven. My other car is a 71 GTO judge I spent 12 years restoring. I also have a 3500 Cummins diesel to pull the stunning 455 posi equipped GTO in Hemi orange with a white vinyl top and white interior to car shows. I'm a mucle car guy through and through. My Prius has Hemi badges on it reading Hemi Prius and Hemi hybrid. The badges came off a 69 Plymoth GTX I crashed 20 years ago.

 

Particularly like this!

 

Good story. Now, what would happen if you traded the car with your wife for a month or so?

 

The wife would never agree to the hit in fuel economy.

 

What an interesting thread!

Particularly interested in your comment, jadziasman:

So, why do they use E10 in the US? Is it because the government passed some stupid law mandating it? If your figures are correct, and typical of other engines and vehicles, then adding 10% ethanol to perfectly good gasoline is actually wasting a whole lot of fuel. Does it make the fuel cleaner burning, in exchange for all the extra fuel wasted? Sounds like a huge false economy to me.

How so? Well, on E0, you were getting 55 mpg. On E10, you get 47 mpg. Let's consider 1,000 miles.

On E0, you would use 18.18 gallons. But on E10, you'll use 21.28 gallons. Since the E10 is still 90% pure gasoline, you'll have used 0.90 x 21.28 = 19.15 gallons of pure gas. In other words, the consumption of gasoline increased by slightly over 5%. And that doesn't even take into account the 10% Ethanol. Effectively, that's 100% wasted as well.

So, if the cost of ethanol and gasoline are the same, effectively, by adding 10% ethanol, you waste 15% more fuel. Even if the ethanol was completely zero-cost, it's wasting 5% of the fuel just to use it.

That's what I'd call typical Goverment Lunacy.

 

What do you call spurious conclusions based on a false premise ?

 

Which is - that jadziasman's figures are wrong? Or...? I did say "If..."

So, please explain.

 

He He, I like the addition of "spurious".

Now, explain!

 

You've already guessed it.

Self reported fuel economy losses with E10 vary widely. I suspect that it varies more or less directly with your political opinion of the ethanol industry, though the type of car and type of engine may also have a small impact.

I've seen people claim anywhere from +2% mileage to -30%. Most scientific studies however seem to indicate about a 2% to 4% loss of mileage with E10.

 

Here you go then:

A 2 second Google search and a bit of thought would have clarified for you that E0 has ~ 3.45% higher heat content than E10, both fuels are almost completely and equally combusted, and E10 does not cause knocking. Since you do not know of any mechanism that might explain a jump up to 17% (55/47) higher thermo efficiency, a reasonable person would be very skeptical of Jadziasman's claims and request extraordinary evidence to back up the extraordinary claim before going off on a rant about the boogey man.

While you are at it in Google, read why ethanol is used at all. Hint: it is not a conspiracy.

Soapbox: Government nonsense is fueled by citizen ignorance.

 

Before I first posted? I would suggest. Sometimes, people play the Devil's Advocate.

 

No, I was simply referring to your previous post which said:

That "which is" was the correct guess I was referring to.

 

Yep, although I for one do not fit that description. I have very little good to say about the Ethanol industry (or the wider corn subsidy) in the US, but I cannot help but laugh a little at the folks who go out of their way to spend 5%+ (and sometimes quite a bit more) for E0 compared to E10.

 

Well, it was midnight my time when I last posted, and I was starting to have trouble reading so I hit the hay...

But I do want to set the record straight here.

First, SageBrush, my friend: you jumped to completely the wrong conclusion when you wrote most of what you said in response to my post. You first accused me of jumping to a spurious conclusion (as quoted above).

Then, you seem to have implied that I didn't think about this at all:

Then, you plainly imply that I am not a reasonable person, next accusing me of "going off on a rant", before finally implying that I'm a conspiracy theorist.

I have to say I was disappointed...

But then, you Americans a not good at subtlety, which is why I rarely watch US movies or TV series.

I guess the other problem is that I speak English and you guys speak American. Not sure about American, but in English, would is a conditional verb. There's usually an if lurking close by. For example: "I would love an icecream (if you're buying)."

So when I said:

I meant: "That's what I would call typical Goverment Lunacy (if it was true... [and I don't think it is])"

I'm afraid you missed that, but hey, I tried. I guess I still didn't give enough warning, even when I said:

I worded it this way because I wanted to leave the question open for people to respond with more information. I was being provocative so I guess I got what I asked for, but I didn't expect to be belittled quite so aggressively.


Anyway, I completely agree with you on this:

I'd go one step further, and say:

"Democracy" is a complete failure!

uart: Do ya reckon I was guessing?

 

For the record, EPA uses E0 for MPG testing and the 2008 EPA change has nothing to do with E10: Explained: 2008 EPA Fuel Economy Ratings

BTW, let's go back to the original topic.

 

The eia FAQ webpage on E10 contains some rather blatant untruths, but never mind.

Ok!

I remember what a mechanic friend told me when I was a teenager, first learning about engines etc.

He told me, "When you pull the head off an engine and see carbon build-up on the top of the piston(s), never clean (scrape??) that carbon off. If you do, the engine will start burning a lot of oil."

I don't know if this was an old mechanics's tale, or whether it's true. Nor, if it's true, do I know what the mechanism would be, but my guess would be that it would be unavoidable that pieces of carbon would fall down the gap between the bore and the piston, and would probably get caught in the ring groove in the piston. If that happened, I guess it would prevent the ring from moving properly, maybe causing decreased sealing and maybe altered wear patterns. Or maybe the carbon simply acts like an abrasive to the bore?

Anyone else heard of this?

My hypothesis is that if this is true, then this may have something to do with Prius engines that start to burn more oil in older age. I'm of the view that the oil burning phenomenon has everything to do with the engine's "lifestyle". As the engine is designed for maximum economy in city driving, I'm guessing that the engine is not at all designed for running for extended periods at high RPM. Instead, they are designed for repetitive, stop-start running at lower RPM. Driving in traffic. Maybe the occasional burst of high power, high RPM, but not continuously.

Having seen the photos of some very dirty, varnished-looking pistons somewhere here, I figure that taking an engine that has carbon build on the piston crown, and subjecting it to sudden hard work at high RPM is going to blast a lot of the carbon buildup off. Some of that must end up in the ring grooves...

My thought is that if you need a car to run at high speed for extended periods, get a different car for that job. The benefits of regen etc in that application will be minimal, and due to all the regen-related overheads, continuous high speed running in a Prius will be less efficient than in an ordinary, modern, economical car.

 

"My thought is that if you need a car to run at high speed for extended periods, get a different car for that job."

I live in an area where the freeway speed limit is 75 mph, and my indicated mpg per the MFD is usually in the low 50's. I believe that this is a lot better than I would achieve in an ordinary economical car.

 

Yes, that sounds amazing! Is that your accumulated mpg, or instantaneous while driving at 75mph? How much time do you spend running at 75 mph (%age-wise), and what do you attribute this great economy to? (Or, do you travel your 75mph freeway in peak traffic averaging 35mph? Surely, at 75mph, the Traction Battery will soon be "exhausted" leaving the ICE to do all the work, so how much do you think having regen really helps? Is it all attributed to being an Atkinson cycle engine?