JET951

O is incorrect ( again ) , 45 deg F = 7.2 deg cel , Porsche printed in the owners manual that came with these last century cars that 20w-50 is quite OK to minus 10 deg cel ( 14 deg F ) , so please " O " ( whatever you actual name is ? ) you have to stop giving out incorrect information

As for a 0w-40 engine oil in a last century Porsche 944 / 951 / 944S2 / 968 engine , what happens when the oil temp reaches operating temp of 90 to 100 deg cel ? , I will tell you what happens , you will damage/ destroy No 2 con-rod bearing at high sustained RPM because the 944 engine will not have sufficient oil pressure to overcome the radially fed crankshaft & to overcome this oil pressure short fall the engine con-rod bearings require sufficient oil PRESSURE ( 20w-50 ) to protect from metal to metal contact & with oil temp of 90 deg cel to 100 deg cel a 0w-40 oil viscosity will not give sufficient oil pressure & made worse as the oil film strength is not up to the application as well

Remember "O" , normal oil temp at high RPM quickly reaches 100 deg cel ( very normal operating temp )

All very basic physics for a very uncomplicated engine

Manx500

0 weight is just 0 on a relative scale, it still has viscosity if measuring on centipose or centistokes via you favorite viscometer or rheometer. All base stocks will reduce viscosity as they heat up, the answer is to add viscosity modifyers. the best oil is one without viscosity modifyers a straight weight.

Stevieporsche

Otto Mechanic

No, it doesn't, but one thing Bruce mentions in the beginning of his post is that, over the course of decades, he's never observed unusual wear due to cold starts. His entire analysis is based on running the engines with low viscosity oils at normal operating temperatures (100C) and high RPMs? He attributes this to the design of these engines, particularly cam, timing chain, rod bearing and lifter wear specifically caused by low oil film strength at normal temperatures.

I have operated my 928 for decades using M1 10-40, for 7 years the car was domiciled in Teton County Wyoming, though I never operated it in winter since I have an aversion to driving high torque rear wheel drive cars on ice.

I think his point is that the relatively brief times the engines are "cold" and filled with a 20-50 oil don't do near the damage caused by running that same engine hot at high RPMs filled with 0-40 for long periods of time? That was the take away message for me anyway.

But hey, it's your engine and your car. For my own part, I'll be using 20w50.

Stevieporsche

screamin94Z

There's not a temperature at which the oil undergoes a step change and suddenly freezes, the viscosity changes with temperature. The concern is not over the initial starting of the engine, its the time immediately following that where the oil pump is trying to push a much more viscous fluid. Since the pump is turning, pressure is there, but you don't get the same flow that would normally be supplied when the oil temperature is higher. Its the reduction of oil flow that is more dangerous to your engine. The engine is designed to run at a certain temperature, and the oil properties are chosen to match the lubrication it needs at that temperature. If the ambient air is much lower temperature, your engine will run cooler in normal driving and could necessitate a change in oil. Refer to the recommendations from Porsche to cater to your applicable temperature range. If your temperatures are below -10C, then 20W-50 is not recommended.

Dan Martinic

That chart is very telling: though it's based on older API standards, it still reveals that a 10w-50--although labelled as capable of behaving like a "50"--actually behaves less so than a 15w-50. And what's with the straight grades behaving so different than the multi-grades?

Clearly, there's a lot of fake news on those oil bottle labels!

I'm just not sure how motor oil producers are allowed to label oils using a standard measure (ex. 10w) even if the oil actually doesn't flow as a 10w in cold temps (10w-60) or label 0w-40 when it can't actually perform like a "40" etc.

Imagine food labelling that was so "off"! Contains 10% sugar ... but actually 50% sorry lol

Peter1800

alordofchaos

No need to imagine, it already exists

Tic Tacs are 94.5% sugar but labelled "0 grams of sugar"
https://en.wikipedia.org/wiki/Tic_Tac
From the official Tic Tac USA site

MAGK944

Dan Martinic

It does have a disclaimer at least. Maybe they should put those on oil bottles too:

0w-50*

*May or may not behave as a 0w or 50 under certain circumstances