2.5 Quarts low after 8300 miles, ok to drive?

As on practically any other engine, yes, anywhere between the dots is ok. Below the lower dot is "technically" not acceptable. Manufacturers likely allow some safety margin below that, but not a huge one.

According to the owner's manual, the distance between the dots corresponds to about 1.6 quarts [1.5 liters], not one quart.

 

Technically acceptable is probably true, but running it below full simply allows it to go below the add mark before you notice it, especially in your case where it appears to have been using oil for several years. The quantity in the system is designed to keep the engine properly lubricated though all operating conditions, including cornering and steep inclines where it tends to gravitate to the front, back or sides of the oil pan. The system is designed to keep a constant flow, so any reduction could lead to problems, especially in an engine that is using oil. Had this happened to you on one of Montana's steep hills, you might be looking for a new engine instead of just wondering if any damage was done.

And yes, I've always filled to the full mark, the way I was taught way back in 1962 when I worked at the service station after school and on weekends. But no, I wouldn't add half a quart, I'd just advise the customer to have it checked again with the next fill-up. Since most folks here seem to think the Prius only needs 4.4 quarts during an oil change, I guess the service center could just put in 4 quarts to get them to the mid point and hope the customer doesn't notice. IMHO, there's a full mark for a reason, so I use it.

 

Then it's worse that I thought, should have checked the manual to be more precise. But being acceptable when checked is not the same as only filling it part way to begin with. Maybe that's why some service centers do such a shoddy job, they're just following the manual? My point was that starting with only 4.2 quarts in an engine that uses oil is not very smart in my book, acceptable or not. Like I said, if it stays at that level, you're okay, but in this case, I think it's asking for trouble. Self-service stations are a far cry from the days when you told the attendant to fill it up and check the oil. I don't care either way, it's not my car, just offering my opinion.

 

There's no undoing this now. Maintain your oil quantity regularly and change it (with filter) more often...until you decide to replace it. Lesson learned.

 

It might be a good idea to use 5W-30 full syn during the cold months and 10w-30 full syn during the warm ones. Most "Treatments" are snake oil.

 

Toyota is definitely having issues with oil consumption in the 2010s. My short block was replaced (right before the 100K warranty expired), because I was burning a crapload of oil. 1 every 500 miles. I think the benchmark was 1 every 600 in the user manual. Adjuster said it was what a previous poster said, oil essentially going out the tailpipe. No clouds our anything, but leaving that way regardless.

 

Thanks for the data point. Unfortunately, the only thing unusual about your story is that you got the short block replaced under warranty. What kind of oil was used in the car before that, and how often was the oil changed? How's it doing now?

 

To the OP?
If the engine is starting, and working?
Sure it's OK to drive.

But as already stated, what is done is done.
It is very possible a varying degree of premature wear and damage was done by running the engine for an unknown extended time with nearly 0 oil.
How this impacts the future of the engine and vehicle is nearly impossible to quantify. You're now charged with having to change your protocol and attention level to the oil and the engine.

But at this point about all you can do is fill it, and drive it, and monitor it.

Personally? I like my oil filled to just a small fraction below the top dot. This makes the oil "Full" leaving a larger room for the use and loss of oil with operation, but simultaneously, not overfilled. Probably to maximize universal use and distribution of the part, Toyota's oil dip stick doesn't say FULL or EMPTY-LOW, instead just giving us two holes, but obviously I operate that closer to Top hole, is closer to full, and anything approaching the bottom hole is approaching empty or "low". I personally want to always keep my oil level at about 3/4ths full in between oil changes. So far my Prius isn't burning an excessive amount of oil and these parameters mean I don't have to add oil in between oil changes, but I strive to check it at least every 2 weeks anyway.

Retrospective admonishment for NOT checking your oil, or catching it sooner, really doesn't do you any good.
Check it now and going forward.

 

It's only been 3000 miles since the replacement, and it's going in next week for a checkup. Standard dealer oil changes with whatever 0W20 (or whatever is supposed to go in there) done regularly, typically every 4-6 mos. It didn't start getting low below the 8-10K changes until around 60,000, and then I started bringing it to the dealer to change more frequently. Right before 100,000, it finally got to the threshold where Toyota Care did something about it.

 

What speed were you driving on a 500 mile trip?

 

Well, honestly officer, the speedometer was plugged to the limit.

I suspect an oil change or two were skipped it no residue is apparent on the drain plug, quietly trade the sucker in and warn friends not to buy it.

 

I'm a little bit lost on the "how fast" and 500 mile joke here, to be honest. Or if that was directed at the OP and not me.

No oil changes were skipped by me. If you want to check my original thread, it's here on PriusChat. I was just chiming in because what happened to the OP happened to me. I had printouts of all my oil changes, done at Toyota Dealers. ToyotaCare scrutinized everything, including the consumption, and approved the short block replacement for me.

As far as my timelines, the short block was replaced ~ 3500 miles ago, at the beginning of February. So, we're looking at ~875 miles a month (I carpool), in Atlanta traffic, doing anything from stop and go to 70-80 on the Interstate. (They drive like maniacs around here.)

 

So after 15k miles on the amsoil looks like this. 64k miles on her.

First trip: 2600 miles. Avg speed 65 mph. No consumption.
Second trip: 2000 miles. Avg speed 68. No consumption.
Third trip 2600 miles and passed 15k on the same oil. Avg speed 75 mph. Seems like 1/8 is down on the dipstick.

Rest of the miles were city driving. Did not notice any oil usage. It looks like the faster you drive, it is more likely to burn oil. I will send this oil for analysis for a clear results.

 

Weird. Maybe a mess up at the last oil change? Why would oil consumption virtually go away? You can't count on anything, lol!

 

When I was in high school working part-time at a service station, my boss forgot to put oil in a new Thunderbird during its first oil change. Fortunately, back then filters were only replaced with every other oil change and the oil light never came on when he took the car back, less than a mile. I don't remember how he discovered his error, but he immediately drove to the house and put oil in. Then he drove it back to the station and changed the oil again. AFAIK, they never had any trouble with the car.