High Oil Consumption

No, I realize mpg goes down during the winter and fall months. But it's pretty substantial and the previous year the mpg only went to like 48.

 

Sorry I'm not on this site 24/7. I do have a business and a life.

 

I have all of my fluids checked by the dealer every 5K. So unless they are lying to me that isn't the case.

 

I aprrecia

Thanks for the thorough helps. I do appreciate it. I'm almost thinking I need to get a second opinion from a reputable shop.

 

Last question first - yes - as this is my business, I have maintained my vehicle properly - Up until this problem at 155K - oil changes with synthetic 0W-20 every 10K and fluid check and tire rotations every 5K. I don't believe a compression test was done - they did a bore scope to check, and found some wear and tear. They suggested changed the weight to 5W-20. Not sure what to think at this point, since I'm definitely not a gear head.

 

BTW, it isn't smoking at all. I have been looking.

 

Make sure the air filter and piping has no leaks to dust out the engine. Replace the PCV valve,(cheap and easy) as crankcase pressure caused by a clogged or bad PCV valve can cause oil conbsumption. Last but not least, most oil CO's sell engine oil with additives formulated to reduce oil consumption on high mile engines. It's worth a try, the high mile oil reduced oil consumption by 50% on my old Dodge Caravan.

 

I brough that up because my wife owned a Satun over a decade ago and this happened to that car. Lucky for us there was a recall:

1992 through 1998 L24 Cylinder heads developed issues with cracks developing in the fifth camshaft journal, located closest to #4 cylinder. The hairline crack would develop between the oil feed port of that journal and the coolant passages in the cylinder head. Symptoms would range from overheating to low coolant, however, most cars affected by this issue exhibited oil migration into the cooling system. The resulting mixture of the two fluids would result in a thick brown "milkshake"-like mixture, visible in the coolant overflow tank.
Saturn released unadvertised policy which would cover this issue, extending the warranty on the cylinder head to 6 years or 100,000 miles (160,000 km).
Repair required the replacement of the cylinder head. and flushing of the coolant system. Badly affected cars would see coolant in the oil, as well as oil in the coolant, and would require the replacement of the complete engine assembly.

 

The other thing to try would be GM Top End cleaner (if you can still find it). Pull all the plugs & pull fuse to fuel pump. Pour a quantity of cleaner into each plug, cover w/ clean towel & allow to sit overnight. Next morning, have someone start vehicle while you hold towel over plug holes to pump out any lingering liquid. Reinstall plugs & fuse for fuel pump. Push vehicle outside and start. Allow to run until mosquito fog function finishes its cycle. Then, change oil.

Sometimes, this will free up stuck piston rings and reduce any consumption being caused by said sticking rings.

 

I do not know what a compression test or leak down test costs, but I do know it is a fairly simple procedure. I've done them on small block chevy V8 engines but that's been a long time ago and never on a Prius.

My experience is that even if consuming some oil, it's not really a major problem unless it becomes so bad that it fouls the spark plugs. Obviously that would start to affect engine performance. Maybe it would impact downstream sensors? (I don't know) You would notice a difference if/when it starts fouling spark plugs and it might throw a code. I have heard that so much oil can be in the combustion chamber that it reduces the effective octane of the gas and the engine starts knocking. However, I have never personally seen/experienced this. Any pre-ignition or engine knock would surely throw a code the first time it happened.

It would be a pain in the arse to add oil every time you filled up with fuel, but other than that you're not going to hurt it further by driving it. I like the idea of adding higher viscosity oil even though it reduces fuel mileage.

 

I'm just asking because I dropped from 52 to 40.....due to cold weather/winter tires.

 

I apologize if you thought this comment was posted toward you. It was actually for the original poster.

 

Excerpt from 2010 Prius manual attached. Toyota cites a 1.1 quarts in 600 miles as threshold for excessive oil consumption. And apparently this is for a new vehicle. So there's no case for a warranty claim.

That said, a sudden change in consumption is a cause for concern. I would:
-- examine spark plugs for a fouled one
-- examine the entire crankcase ventilation system
-- re-check for leaks onto the driveway

 

Let me ask you a question. Would you be perfectly happy if your new car burned 1.1qt oil in 600 miles?

 

No, but statements like this are fairly common for new car warranties.

 

... and just to be clear.... the car we are referring to in this thread has 185,000+ miles.

 

If you do a web search for "toyota excessive oil consumption" you'll get an alarming number of hits for Corolla, Camry and RAV4 and all problems seem to relate to piston ring issues -- wear or sticking. There's no talk about any other problem such as leaks or valve-seal failure. Could the Prius design be similar? And is the transition to synthetic oil a measure to prevent sticking rings? Did the OP accumulate a significant number of miles before synthetic was mandated?

 

The short block (engine below the head) of a Prius is pretty the much same as a Corolla, right down to part numbers.

Edit: The piston rings do have different part numbers though

 

Interesting information, yes, the Prius engine is an Atkinson cycle version of the 1.8 liter engine used in the Corolla.

BTW the 2010 owner's manual and maintenance manual make no mention of a synthetic oil requirement. The requirement is for 0W20 oil which is, at this time, available only as a synthetic (or maybe a semi-synthetic from Honda). I believe the requirement for 0W20 was to help eke out every last tenth of a mpg to make sure the company meets the CAFE standard. Toyota sells a lot of SUVs and Trucks which don't get very good mileage.

 

You are right, but only partially. The engines that are oil burners are 1998-2002 1ZZ-FE (Corolla) and 2002–2009 2AZ-FE (Camry/RAV4). 3rd gen Prius is based on 2ZR-FE and that is not know to be oil burner, except for early 2008 Corollas, that was fixed by firmware fix.

But you are right about sticking oil ring issue in those engine. I know it for a fact as I deal with oil consumption in my corolla made in 2002. This is why I mentioned in my post (somewhere above) that engine oil flushes and piston soaks are very helpful.