Question about temperature and oil viscosity

That's why you have COOLANT. It doesn't boil off like water. And why engines have
a "212" switch. That's usually when the fans come one, give or take.
Thicker oil doesn't prevents oil burning. It just makes the engine work harder.

Because tolerences are much much tighter in engines now you can use thinner oil.
Which provides less resistance, thus more mpg.
Everyone has a gimmick to get people to buy their product. The valvoline restore and protect
is a good example. I've been usinging it for 6 or 7 oil changes and I'm still using the same
amount of oil before I started using it. So it hasn't worked for me. I was hoping that MAYBE
it would clean up the clogging around the rings, but it hasn't.

 

A gen3 burning oil is caused by stuck piston rings and is made permanent through increased cylinder wear. Thicker oil (higher viscosity) and various oil treatments like B12 won’t help. If you catch it quick and change the pistons and rings with revised parts, the excessive oil consumption will stop. For most, the repair is a replacement engine, usually JDM or rebuilt.

A 50/50 blend of antifreeze boils at 223f; a 60/40 blend has a higher boiling point. A 15 psi pressure cap in an engine without a pressure leak (head gasket fail) adds another 45f to the boiling point of 50/50 antifreeze.

The best thing for the engine is to change the oil religiously at 5k miles and drain and fill the coolant at 30k-50k miles. I do 30k miles.

 

G3 head gasket failures are due to an OEM design fault (EGR cooler) exacerbated by a small engine sump, overly long OCI, and customer maintenance.

Doubt me?
RTFM.
Oil and fluid checks are called for at 30 day/1000 mile intervals.
IN NEARLY EVERY CASE regular fluid checks would cause the customer to detect and mitigate the EGR problem before a loss of coolant leads to the "Prius Death Rattle" and causes a bottom-end failure.

SO...
How often do YOU raise YOUR hood?

@ Heat.
If this was really a 'thing' engines would not need thermostats.
They would have big, fugly radiators with always-on fans (which would match those BF grills!!!)
AS IT IS......if the engine temp is 210 then the oil temp is pretty much the same.

@ Oh Dubbaya 16-12-8....etc
easy.
CAFE and Warranties.

PHEVS are warrantied for X miles and X YEARS.
If you have people jumping through their butts to keep the engine from turning over for weeks and months on end with a PHEV - then HOW GOOD does the ICE have to BE???

After all - at some point it's just a 'range extender' - right?
If you can squeeze another mpg or two by thinning down the oil - what DO YOU think they're gonna do???


OEMS care deeply about the bottom line.
PERIOD.
Full Stop.
Chock the tires!

 

How many miles?

The head gaskets fail due to heat cycles? 2nd and 4th Gen just got lucky?

I’d recommend full EGR system clean, including intake manifold, at least every 50k miles.

 

Water does not have to be 210f or higher to turn to vapor. Water will evaporate at 70f or 150f or 195f. Boiling just does it faster.

Concerning water or fuel in the oil, sure we don’t want it but fuel dilution is way more of an issue - in fact it is an important factor causing stuck low tension rings as that area is ground zero for fuel / oil mixing and resulting dilution. Changing the oil on a problem engine is therefore much more important.

 

Extreme low viscosities like 0w8 are more about mpg than clearances. Don’t get too carried away with increasing viscosity as too high viscosity can damage your variable valve timing.

 

It's YOUR engine. Do with it as you please.