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

sounds like as good a theory as any. i have no idea, but i wonder if synthetic will reduce this in gen III?

 

JC91006,

It's a good theory and may apply to some instances of "The Burn" but there are so many different things that can be causing excess oil usage to attribute them all to one thing doesn't hold water, IMO. Ema for one seems to debunk this theory because I almost never drive before the engine starts because I am programming in customers to the GPS or moving crap around or something.

Ema seems to support "striae" wearing down and not holding oil as well. This was mentioned by Rude person's mentioned in the "Low Oil Horror Story" thread you have replied in. I guess this is actually engine wear so supports your theory but isn't necessarily from cold starts.

There is an interesting article in the ASME magazine this month called "Cold Start ... Dead Sensor" talking about how oil acts as a dielectric on cold starts and can take out sensitive engine components. The article is talking about jet engines I think, haven't had a chance to read it yet just skim, but it is also something to look at.

Anyway my $0.02 is finding a primary root cause for oil burning will be engine specific and no single cause would be found. Sometimes rings, sometimes valves, sometimes wear, sometimes overfill, carbon buildup, etc... etc...

Happy driving,
Chris

PS - I ordered some Liqui Moly and am going to give it a shot, LOL.

 

If hv-battery has enough charge and your gentle with gas pedal ICE doesn’t get any more wear than if you waited.

 

[/QUOTE]
Did you buy your car new and always waited til the engine kicked in before driving? My theory is for engines that started burning quite early in their life. I'm trying to figure out why some people (my 2010 with 65k miles) started burning oil at such a young age.[/QUOTE]

Yes, I bought Ema new in March 2006 and have almost always waited for the ICE to start before driving. As documented in other threads my oil burning has improved dramatically with the switch to pure E0 gas. It also never really got any worse after I started limiting her to 4,000 RPM and under by watching the scangauge.

Chris

 

I never let my engine start when I drive from home. Living near the top of a hill I drive "or roll" down in EV mode regening and when I get to the flatter section of road the engine starts when I reach 31 mph. The car uses no measurable oil between 10k mile changes, and is now at close to 110k miles.
The car has only had 0w/20 synthetic oil since the first oil change. The first 50k miles were mostly fast motorway miles the rest mostly rural driving in the 50 to 60 mph range.
I believe the engine warms quicker under load, and perhaps the lighter oil circulates more readily.

John (Britprius)

 

I have a 3 mile commute and have found that I get better mpgs on both legs if I let the car warm up and go into ev (about 45 seconds) before proceeding. I have started doing the same for long trips also. I am in Florida so the warm ups are usually on 45 seconds.

 

I get about 3/4 of a mile free energy recovery from my downhill run. Some of this of course is used to assist the engine on the flat as it warms up. If I let the engine start and warm up before moving off the battery gets full before I reach the bottom of the hill, and is unable to accept the extra charge so wasting energy.
Our temperatures in the UK are well bellow yours, but we also do not have the dreaded thermos tank so less coolant to warm up from a true cold start.

John (Britprius)

 

I am in Central Florida coast so the biggest "hill" is crossing the railroad tracks.

 

This is another oil thread where people are going to disagree heavily as always, but here is my two cents. Fact - All motors need to have good oil pressure and initial warm up for expansion before you put a "load" on them. When researching whether or not to buy a Prius, I read the many "tricks" owners did to get the very best mpg...including driving right off after power up or achieving "Ready" mode. Statements condemning regular car drivers for wasting gas idling for any period of time after start-up were and still are common. My "opinion" is at minimum let the engine go through it's first warm up cycle and shut off before driving and don't just punch it right away to get on the freeway or what ever . My "opinion" also includes changing with suitable oil and filter sooner than the "minimum" recommended by any mfg and checking the level at every fill up to be aware of changes. My Prius now has over 75,000 mile and does not burn any measurable volume of oil and this has worked on all other vehicles I have owned. Discussing any other variables or arguments people wish to explore is fine, but this works for me...and I make a living as a mechanic. YMMV

 

I am also starting (at this late date) to warm up our Prius for a minute before driving. But my wife will never agree to this sort of thing, so its of questionable merit.

In any case, I don't think our Gen2 ever gets up to 25 MPH before the ICE comes on. If Gen3 does, then maybe that could be a reason for Gen3's to have more wear. Seems like your comments JC are related to your Gen3 oil losses.

I do not know what causes it (oil losses) but believe some have blamed crud/varnish build-up on the pistons/rings (whatever we got in there) so I assume not letting the used oil get too crappy may help, as well as a new oil filter. But I go about 7000k miles on synthetic oil before changing.

 

Your assumption of no oil circulating at startup is wrong. Engine is spinned by MG at 1000 rpm for a little while every time BEFORE any gas is injected in it. So everything is well-lubricated when the load on the engine starts.

- Alex

 

That was confirmed 14 years ago. We were told directly by Toyota itself how startup worked.

The smaller of the two motor/generators is used to spin the engine up to idle speed and is kept there until oil-pressure is established.... then fuel & spark.

That's dramatically less stressful on an engine than the usual spark & pray method, where it's spun to just a fraction of that speed for only a brief moment.

 

It does, if you listen carefully.

I've heard it in parking lots, where you have to look around because you don't initially see the HSD vehicle but know it's somewhere near by.

The sound is subtle and the hood area insulated. But it is distinct, not like the rough noise all of us grew up with.