Rigid 15 000 Km oil changes makes no sense IMHO

No one can objectively and with overwhelming proof tell you that you are right or wrong. All you will get are opinions, some of them very strongly argued and/or held opinions. This even includes the opinions of Toyota and auto manufacturers and of course oil companies and sellers.
But if you want to avoid denial of warranty claims you pretty much have to do what they say whether necessary in fact or not. My own, unproven, opinion is that you will get to the design service life of the vehicle and engine even if you never change oil as long as you don’t let the oil get low. But I won’t bother arguing the matter. Good luck

 

Toyota also stipulates “yearly”?

 

in the US, a manufacture can refuse warranty claims if you did not follow recommended service intervals. no idea in Portugal.

 

Except that there’s no way Toyota can tell if you changed your oil or not Jumbo.
So the warranty thing is a fallacy you keep perpetuating

 

You could have the oil tested, but that might be an unnecessary expense .
However, testing it once might tell you everything you need to know

 

This is the way.
$40 well spent, though it kinda eats into the "save a few bucks by extending the OCI".

 

This is the way.
$40 well spent, though it kinda eats into the "save a few bucks by extending the OCI".

 

He's right. The oil keeps lubricating, but protective additives get used up over time. In time, the oil becomes acidic, and more metal to metal contact happens on start up and high loads. The oil change is to replace those additives.

Toyota is just sticking to what they call for with their non-plug-ins cause it is easy. In their defense, it would be hard to pick a mileage or time number that would be safe to cover to potential range of EV miles a car could see.

GM and Honda use a system that monitors temperatures and engine parameters to determine when to change the oil. A Volt could go two years between changes.

The simple solution to reduce oil use with PHEVs as ones with longer and longer EV ranges come out would be what other industries use; engine hour meters.

As for your question, you could safely go with longer intervals when out of warranty. Oil analysis can help with that.

It would only be a cost for a handful of times. Once the change point is pinned down, it is no longer needed for the car sticking to that use cycle.

 

Yeah, that's the quandry.

 

About the engine warranty...if you bring the car in with engine problems and the insides are full of black goo, no warranty repairs for you. If the insides are clean and oily, you'll probably get the repairs without problem.

Oil certainly does degrade with use. It oxidizes and turns to sludge, as well as the essential additives getting depleted...anti wear agents, anti foamants, anti oxidants, corrosion inhibitors, viscosity index improvers, pour point depressants, alkalinity improver, and others, about 10 to 30% of the finished oil by volume.

Used oil is collected for several uses. A certain percentage can be introduced into the crude oil stream in a refinery and refined along with the crude. Used oil can be re-refined into a good quality lube oil. It can be used as part of the oil to make asphalt pavement and other asphalt products. A limited amount can be mixed into heavy fuel oil as cutter stock to improve the viscosity and specific gravity. In any case, it is not wasted nor just dumped.

Back to the Prime oil drain interval...we probably use the engine perhaps 10 to 20% of the miles. No need to change that oil. Nor is there any good reason to have a 1 year interval. I've had diesel engines in intermittent use with the same engine oil for years, but we did quarterly oil analyses. Toyota picked a simple minded way to set the oil drain interval, and we're stuck with that unless you want to do periodic $35 analyses.

 

I wish Toyota would come up with a way to know just how many miles we've put on the ICE engine, especially in the Primes. I monitor my hybrids while driving and, sometimes, the engine doesn't seem to run but about 30% of the time...so if I drove 45 miles the ICE only ran for 13.5 miles. This would greatly extend my rule of changing out the oil every 5,000 miles. (So I'm, probably, changing more like every 3,000 miles of engine run time.)

 

I think you have to answer that.

 

No. Reduced use of the ice especially with stop start leads to increased fuel dilution that does not quickly evaporate off and causes increased carbon on upper engine parts experiencing thermal cycling many times per drive rather than once in a conventional drivetrain. You want the detergent additives to be at their most effective state.

On my 2022 Rav4 hybrid there is a percent of ev operation that can be displayed. Typically I see 44% plus or minus in a vehicle with 90% highway driving. However I would never extend oil change intervals even to 10k miles much less more.

 

Aside for some extreme use cycles, the additives will get depleted before the degradation leads to sludging.

It was a common practice back when Porsche made the comment. My father says he would just let the oil drain onto to gravel driveway back then. I suspect he wasn't unique for the time.

Today, drips and spills still happen when oil changes are done, and the recycling has a cost to it. While greatly reduced compared to the past, there is still an environmental cost to too frequent oil changes.

Toyota chose to simply use the interval they picked for their ICE models.

High EV ratio in a hybrid could mean the engine sees the equivalent of short trips, which lead to shorter oil life.

That may not be true for a PHEV. The EV miles can be from trips that the engine never turns on, and trips with engine use can be ones that adequately heat up the oil.

 

When I was a kid the gas station ‘cross the road routinely dumped used oil out back, down a small rock outcrop. It literally looked like hell.

the stations still there, though pretty much eclipsed by the corporate self-serves in town centre. The dump areas all overgrown, but guess it’s all still there.

 

The oil finds its way down to ground water or is washed off into streams and rivers. Not good either way.

 

That's true...the start/stop technology found in many vehicles these days does introduce new wear-and-tear. Many vehicles even have a button allowing the driver to turn the feature off. I'll just keep doing my 5,000 mile/6-month oil changes and see how many miles I can get my Prius...never had a vehicle hit 200,000 so keeping it for the long-term. (I'm averaging 15,000 miles a year so should hit it in 2034.)