Low oil pressure every 6 weeks or so but no apparent leaks

Just editorial, should that be 0.5 quarts, AKA: one pint, or 2 cups?

There is no oil level detector, just low oil pressure. But the two kinda go hand-in-hand. Except that by the time the car reports low oil pressure it's virtually dry.

Roughly how many miles would you put on in that 6 week interval?

The 2012's have the lower tension piston rings, and that's been a common contributor to oil consumption, when the rings, and oil passages in the pistons, gum up with carbon.This in turn allows oil to get past the rings, into the combustion chamber, and carbons up the rings/pistons even faster. It often starts somewhere between 100K and 150K.


How many miles on it?

How often are you changing the oil, per the US miles spec (10K)?

Maybe cast a vote here:

3rd gen model year and oil consumption | PriusChat

 

The 2010-2014 Prius engines have a flawed piston and piston ring design that often causes "excessive" oil consumption. Toyota would replace the parts if oil consumption was "excessive" while the vehicle was still covered by the 60,000 mile 5 year powertrain warranty. A Toyota tsb was specific about the issue for those years. "Excessive" is defined by Toyota as one quart every 1200 miles. So its pretty easy to burn almost all the oil in 5,000 miles.

The catalytic converter, egr and pcv system combine to consume the "burned" oil so you don't see it.

The downsides from excessive oil consumption can be a) engine oil starvation and wear throughout the engine b) clogged catalytic converters c) an overwhelmed pcv system that collects oil in the intake and d) excessive oil flow through the egr system clogging it as well. A combination of these symptoms can result in head gasket failure. Many focus on cleaning up the egr, pcv and head gasket. Unfortunately it is often a fruitless attempt without repairing the root cause, eg the piston rings and scored cylinders.

Many believe Toyota was additionally complicit by recommending 10k mile oil changes reinforced by two free changes in the first 25k miles. 5k oil changes may have saved many of these engines but it is too late after excessive oil consumption has already scored the cylinders.

In a more logical time, most would trade or junk a 200k Prius with these issues. Certainly one can check and top off the oil every 1000 miles or every three fillups and hope for the best. In fact statistics show just 3% are still on the road with high miles. So all the miracles we hear about are the exception to the rule OR have replacement/rebuilt engines.

Often engine replacement/rebuild is a good strategy if you want another three to five reliable years. Pricing varies from $3k-$7k depending on location and availability of experienced independents. Some are even fitting gen4 redesign engines, usually with gen3 manifolds and egrs.

I would only go that route if the car already had a new brake booster (a $2.5k failure not covered over 150k miles). A decent high voltage battery new in the last three years would also be a prerequisite for me.

In the end the dealer may be right when they suggest its worn out. So some will trade, some will frequently top off the oil and hope for the best, while some will replace or rebuild the engine.

 

Yeah, you can't keep letting it get to that point. The "oil" indicator in nearly all cars (especially older, domestic ones) is an "oil pressure lost" indication. Any kind of oil "level" sensor is a rare and upscale feature. (I have never owned or even touched a car that had one.)

When the oil pressure light comes on, the oil level has dropped below the oil pump intake, no oil is being pumped, and the engine is being actively destroyed with every additional foot that you drive.

Once that has happened a few times, it will be happening sooner and faster after that.

It is best to check the oil level regularly, using the dipstick, and never let it get more than a quart or so low.

 

Diy is not a great idea for a rebuild. First you buy a low mile replacement engine and then have it rebuilt using the services of a first class engine shop. If you do the installation, maybe $2k-$3k with two days of downtime for swapping the engine with experienced help.

 

No they don't.....unless it is followed by the word "pressure".
If there IS an oil level alarm, it is an unusual and unique model.
That has NEVER been common.

Most any vehicle with 200K miles will use some oil, due to worn piston rings and valve guide seals without "leaking" any out.
Some more than others. Apparently yours is more.

P.S. Every time that low oil pressure light comes on, you are doing additional damage to the engine if you continue to drive it more than a mile or so. One day, probably soon, adding oil won't fix the problem anymore.

 

Older Chevy trucks(99-02) had a add oil light that came on. May have been an option I’m not sure. They had a sensor that was up high on the oil pan once the sensor was out of the oil the light would come on. Basically two court low. Ironically the newer trucks do not have it. Just the red oil pressure light. Side not the newer Chevy trucks typically burn more oil then the old ones. LOL

 

Sure there are probably a few other exceptions too.
If you go back far enough, before idiot lights, there was an actual oil pressure gauge.
I don't think there ever was an "oil level gauge".

 

Yeah, worth heeding: "low oil pressure" warning means just that, oil is not getting where it needs to get.

 

Many cars do measure oil level including Lexus, just not a Prius.

 

Real.life as today in SE USA Durham NC bought 1 8 ltr and cvt w mg1 and 2 delivered to my door 1,248 cash looks brand new 2 pieces strapped to pallet it goes in Friday ready Saturday. 650 to install plus oil coolant cvt oil etc so I'm at 2K don't know condition of HV battery was fine been sitting 8 months. Here we go again. He he 13 persona with mileage conflict. Dash says 202K tech stream says 270K I want to kill off oil probs.