Oil Change: 18 Months Or 15,000 Miles

Bulk oil here, got tired of adding countless oil contam’d bottles to the “recycle stream”.

 

My 2¢ worth on oil change intervals for PHEV vehicles: Since there is no way that I know of to get the Prius Prime to display the actual run time on the ICE on the car's instrument panel, it is necessary to get an OBDII scanner that can read PID codes. PID 7F (Mode 1) is supposed to be the total run time on the engine. I have not tested this yet since I don't have an OBD scanner dongle, but I have one on order. If your average driving speed is 50 mph, then it takes 20 hours to drive 1,000 miles. Now, Toyota states oil change interval for Prius and Prius Prime as 10,000 miles/1 year. I am not comfortable with this, for the following reason: Even the best oil filters only trap carbon and metal particles down to about 5 microns in size. The OEM Toyota 90915-YZZF2 filters probably aren't quite as good as the top-of-the-line K&N filters, and I'd guess they only catch particles >8 microns. So over time, the motor oil is accumulating an ever greater load of ultra-fine carbon particles that are too small for the filter to trap, and the high-speed moving parts of the engine, especially the piston rings and crankshaft bearings, are being continuously exposed to this ultra-fine grit. It is my gut feeling that if you intend to have your car for a long time and get 250,000 or more miles of life out of the engine, changing oil more frequently will help you achieve this.

Now, 10,000 miles would more-or-less equate to 200 hours of run time if all of the driving was on the freeway. But if you mostly drive in city traffic, you might accumulate 200 hours of run time in only 5,000 miles. In 10,000 miles in a Prius, you would have burned 180 gallons of gas. In a Prius Prime, that's harder to determine unless you keep track of actual gasoline purchases, which I do. So, if 10,000 miles takes 180 gallons of gas, then 5,000 miles takes 90 gallons, and that's how I do my oil changes in a Prius Prime: when I have burned 90~100 gallons of gasoline, I do an oil change, whether the oil looks dirty or not. In a newer Toyota, the oil probably won't look dirty yet at the "100 gallons driven" mark, but I change the oil anyway, to get rid of those tiny, <5 micron size, carbon particles and metal shavings that the filter isn't catching.

 

Just for your information, PP displays EV ratio for the life on Drive Monitor. If you never reset it, the number corresponding to ODO is for the lifetime. This is the % of the EV-driven portion. Note this is not EV Mode driven portion, meaning it includes both EV mode and EV portion of the HV Mode. Thus one can estimate what % of ODO miles are actually driven on the gas engine.

This was the photo of my 2017 PP on the last day before I traded it. ~40kmiles and 60% were on EV. Thus the engine run ~16kmiles. During this period ~2.5 years, I had 3 oil changes and was due for the 4th oil change if I kept the car. So the average engine miles for the oil change interval was ~5300miles. I think that's good enough for me. Especially for me, considering no car is going to last longer than 10 years in our climate without major rust-related issues. I have come to accept the fact that as long as I drive in winter, I have to replace my car before the engine failure.

 

Mobil 1 Advance 0w16 is only warranted for a 5 year shelf life, 10k mile or annual oil change required - there's also an OEM disclaimer. So it looks like we're required to do an annual oil change. Neither the official Valvoline or Castrol websites list details of 0W-16 oil - just hasn't been updated, since their oil is on the market. At least I couldn't find it.

Mobil 1™ limited warranty | Mobil™

I'm burning about 8 gallons a month, assuming 53 mpg on HV - my 10K mile ICE change interval would be 22.5 months. I was going to split the difference and do a 18 month change interval, which would put me around 7500 miles. If all the oil providers place this sort of disclaimer on their products; we're forced to do annual changes.

 

You’re not “forced” to do much, if anything. Still, it’s good to make informed decisions, set your own rules.

 

I stand by 75% of recommended mileage ( 7500 vs 10000 ) for oil change or 6 month which ever comes first...
That may change as I moving onto new vehicle with new recommended oil change interval...

Posted via the PriusChat mobile app.

 

I changed the oil in the Chevy Volt that I used to own 3 times in the 70,000 miles that I drove it. The Volt's computer tracked engine use and based the oil change interval on that rather than a hard limit based on total vehicle miles driven. I believe the car would demand an oil change after around 7500 miles of ICE driving or 2 years.

One of the questions I asked the salesman when I bought my Prime was about the oil change interval, I was surprised to hear that it did not function like the Volt. So far I am around 85% EV with 8500 miles, I plan to change the oil every 10k miles as recommended by Toyota but I would not hesitate to wait longer based on my driving if I weren't concerned about maintenance logs affecting resale value or potential warranty work in the future. If I had a conventional Prius then I would get the oil changed every 5k miles, but the engine in my Prime sees so little use that even doing it every 10k feels like a waste. It seems like an attempt to compromise without developing complex software to track the engine use for the maintenance reminder like the Volt had.

 

2010 Priuses burning oil is due to an engine piston ring design flaw, holes too small, along with the EGR cooler getting clogged.

 

I'm following TCCN advice and doing them more frequently! As close to 5k as I can (drive probably 25k/year, down ftom 60k a few years ago!) With his videos I've started doing my own maintenance, so 15 min and $25 I'm g2g.

 

I haven't seen many UOA results posted throughout the site or on Boboilguy to confirm the original poster's inquiry/plan of attack. Saw a couple of posts from very early life oil analysis on break-in. Curious what it tends to look like at higher mileage, as I also have quite low ICE mileage/year and am tempted to stretch to 18 months.

 

what are you driving? i see a 2009

 

Oops - profile updated - thanks for reminder. 2020 Prime in the stable now w/ ~150k miles on the clock so the warranty is not my concern. 09 gone but not forgotten - preventative maintenance only and never skipped a beat, still got ~48-49 mpg in 2023 w/ ~125k mi, down from 49-50 years prior . Mr Prius showed it as a healthy 15 year old battery.

I want to treat the car well so it lasts as long as possible while not wanting to spill any more oil on myself than necessary to do so. I am going to check my EV% when home, but avg ~110+ 'mpg' according to monthly chart if memory serves. Sometimes go weeks without the ICE coming on, occasional long trip that bring down my avg. Love this car.

I assume the 10k/1yr recommended is playing it safe as Toyota doesn't know (or bother calculating) any of the many variables into any given driver's patterns. EV%, climate, air quality, etc. Oil manufacturers aren't going to warranty anything longer than they need to. I drive much less than original owner... if I'm realistically only operating the ICE for 1-2k miles a year it seems a bit over the top to me to be changing out the oil at the same rate as a typical ICE or to lesser extent hybrid... but I'd like to see some science to tell me I'm not being pound foolish before I go experimenting.

 

Someone posted their oil results on reddit yesterday, and since I only just had my 1st oil change on my (newish to me) 150k miler, it had me searching the priuschat forums again for any analysis results. Poster on reddit had very low insolubles and high TBN, but they only had 6300 miles on oil and 25k on car.


Interesting and related from Blackstone Labs (humorous) FAQs re: oil time vs mileage question:

I took a sample three months ago and forgot to send it in. It’s been on a shelf in my garage ever since. Can I still send it in? Will the results still be good?
Should be fine.

Okay but the oil was in the engine for more than a year. Is that a problem? Will it affect the analysis?
No. Oil doesn’t wear out by just sitting there. It only breaks down as it’s used and accumulates metals/contaminants. In Ye Olden Days, engines weren’t sealed up tight. They had open breathers that allowed moisture and other contaminants to enter the engine when it loafed around, unused. That’s not the case these days. If you don’t have an open breather, your oil can sit pretty much indefinitely without going bad.

Are you sure?
Yes. We know things.

 

i don't have any useful info. i used to change my plug in oil once a year, because i was concerned about condensation.
but i always felt like it was a waste of resources