PCV and Oil Consumption

Yes, jadziasman, I'll give you that 60% may be unrealistic. I think we do need to account for coasting and P&G in this example. If I speed up for the first .X mile then notice the light ahead is red, I let off the gas and begin to coast. The ICE shuts off and I'm using no traction battery (on the contrary, I'm charging the traction battery). I glide to the stop sign for the next .X miles. The light changes and I speed up to 35-40 mph and hold. Every time I let of the accelerator (either because of a downgrade, someone tapping their brakes ahead of me, the ICE shuts of (without using traction battery). While maintaining 35-40mph, the HSD cycles the traction battery as you state above. I am clueless as to percentage of ICE usage this would net but def less than 100%.

Yes, I agree so the 60% is probably too generous but the main point is that the ICE isn't running all the time and therefore should receive less wear than an ICE on a standard car. We can always dig deeper in the weeds on any issue and find evidence to refute or validate a claim but that's not what I'm trying to do here.

I probably should have just made a general statement that the Prius ICE doesn't run 100% of the time since that was the point I was trying to make. I didn't foresee the firestorm ahead. Sorry!

 

Another point here is that when the Prius engine is running it is often running at a lower rpm than a conventional car. This must also be a factor in engine ware and subsequent oil consumption.

John (Britprius)

 

Yeah, I mentioned the lower ICE rpm in a post yesterday or the day before. I'm sure that's a factor.

The "excessive" oil consumption concern with some Gen II's with >150K miles is puzzling.

I believe my 05 consumes oil because the prior owner had been provided with poor quality dino oil changes at the stealership. I would imagine the stealership is SUPPOSED to use the Toyota brand motor oil but I'm not sure they were actually doing so since you usually can't see the mechanic working on your vehicle at the stealership. And I doubt the previous owner, who is female, ever checked the oil level on the dipstick.

Anyway, she had oil changes every 3000 miles (the maintenance history shows she paid for them anyway). And she apparently isn't frugal (like me) because she had paid about $4000 in maintenance during the 5.5 years and 134K miles of ownership. She had the 30K 60K 90K and 120K mile services performed, which are quite expensive (and totally unnecessary for the first two IMHO). She also had both HID bulbs replaced for $700 - ouch! Anything they could charge her for they did and she apparently had no problem forking over the dough.

I suspected there was an issue with the engine oil when I test drove the car. I saw oil varnish inside the cylinder head after removing the oil fill cap after the test drive. The varnish wasn't dark brown or thick but I still don't like to see any oil varnish in there at all (both of my Honda Civics had no oil varnish in the head after 200K miles). I decided to buy the car anyway because it was a good deal, it drove and sounded fine, and it was in immaculate condition otherwise.

My theory for the oil varnish that has accumulated inside the cylinder head is that the oil the stealership had been pouring in was of poor quality. The oil did not hold up well to the temperatures in the head and degraded between changes. It's my belief that the cylinder head temperature for many Toyota models is excessive even though the head is liquid cooled - the coolant flow rate is not sufficient to keep the entire head at a uniform temperature (there are hot spots).

And, I think that the oil drain back holes may not be large enough diameter or there aren't enough of them. It was amazing how quickly I could pour oil in the Civics - they would take it as quickly as I could pour it out of the wide mouth liter containers through a large funnel. I can't do that with the Prius. So, the oil flowing through the head is possibly at a higher temperature than it should be.

The oil consumption issue may be related to the oil varnish in the cylinder head and its effect on temps in the head. I would guess that the cylinder head temperatures had been too high for quite some time which degraded the valve stem seals more quickly than they normally would. The car has 190K miles and it is using about 1 qt every 4000 miles which is not excessive but is annoying nevertheless. That's my theory.

And no, I'm not going to search for the precise root cause for the oil consumption on this car and I'm definitely not going to try to remove the varnish deposits with Seafoam, AutoRx, or specialty additives - I'll just continue to top off the oil as needed. I'll change it every 5000 miles with Mobil 1 and just keep driving it until the wheels fall off. This also gives me a regular opportunity to check under the bonnet to keep an eye on the other fluid levels as well. I typically check after every other fill up with petrol.

 

The oil should drain back quicker in the Prius as it has a timing chain giving a direct route to the sump from the top of the engine. I agree with your cheap oil theory as my own engine is still spotless at 90,000 miles using only Toyota or Mobil 1 0w20 oil from it's first oil change, and no oil use (measurable) between oil changes at 10,000 mile intervals, the recommended interval in the UK.

John (Britprius)

 

Hi jadz. I'm thinking that if the previous owner only did 13k in 5.5 years, then those 3000 mile services could have been up to 18 months apart. This also implies lots of short trips. Combine all those factors (cheap oil, 12 to 18 month OCIs, and lots of short trips) and your pretty much asking for sludge formation.

Yes you're doing the right thing. Using 1L per 4000 miles is definitely only minor oil consumption. The best thing to do is just feed it the oil it wants, when it wants, and keep on running it.

 

That's a typo - she had 134K miles on it when she traded it in. I tend to revise what I write several times and missed that.

 

As recently as three decades ago, vehicle owners were impressed if their car's engine would last 100K miles without needing major work. For example, I recall my 1985 Jaguar XJ6 Vandenplas needed the cylinder head removed and rebuilt at 70K miles. (Of course, Jaguar has never been known as a brand that offered world-class drivetrain quality.)

Now, your car uses 1 quart of oil in 4K miles after logging 190K miles and you are annoyed by that. That is progress.

 

I had breakfast with some fellow automotive enthusiasts yesterday. We all had our automotive formative years in the late 1950s early 1960s and we were discussing the good old days. We came to the conclusion that anyone who thinks of the 50s and 60s car as pinnacles of anything either weren't there, are looking through a rose colored rear view mirror or have dementia.

 

IMO, people who collect 50s and 60s vehicles do that as a way to stay in touch with their high school years. I agree that generally those vehicles are sad, compared to newer models.

One positive attribute is that you don't need much model-specific information or fancy tools to perform basic services. The flip-side is that those models typically need service much more frequently.

 

While I agree 50's 60's cars rusted away to quickly needed constant greasing and servicing and by to days standards were poor performers, there is still something eye pleasing in there design. I have four vehicles 3 of which have been in the family since new, and all still run. They are:-

A 1954 A40 somerset. Was my farther's first new car.
An Austin Healey 3000 (1960) bought new.
An MGBGT 1966 pre production car bought from the factory. (Not considered new as it was first registered by MG)
An series 1 roadster E type Jaguar bought new.

These cars are not for sale and are being passed down the family. They are however used in the summer but being unmodified fuel is difficult to come by in true leaded form.

John (Britprius)

 

Nice collection...

To focus on just one of those, pls tell us how many miles the E-Type logged over the past 50 years and what major repairs have been performed to it.

 

The E type has only done 120,000 miles. No major engine work (heads never been off), gearbox not been touched. All universal joints replaced and shocks. Some minor paint bodywork and new hood. All the cars now only go out in dry weather and are stored wheels of he ground (suspension hanging) Engines are run monthly.

John (Britprius)

 

Thank you for preserving those cars in operating condition.

 

Wow, nice there collection John.

 

Back to the issue of oil consumption. It's interesting to calculate just how little oil is lost per piston (up/down) cycle to consume 1L per 4000 miles. Here's an estimate.

2000 rpm * 1.25 min/mile * 4 cylinders * 4000 miles = 40 million piston cycles.

This works out at 25 nL (nano-liters) per piston cycle.