5w/20 oil OK to use?

[prpmmp]

Originally Posted by Allanw

I think the guy who came up with the "system" should be shot! there are far easier ways, that would be easier to "get".

MOST people (inc mechanics and piles of people on here) still don't understand it (even if they think they do )

Oil thickens when cold, 5-20 thickens less than 5-30 but at 212 degrees both have the same flow. Did you ever drain your oil when hot? Flows like water and is protecting your engine in that state! http://ferrarichat.com/forum/faq.php?faq=haas_articles Read the whole article, there is a piece about older engines and oil thickness. Pete

[Allanw]

Originally Posted by prpmmp

Oil thickens when cold, 5-20 thickens less than 5-30 but at 212 degrees both have the same flow. Did you ever drain your oil when hot? Flows like water and is protecting your engine in that state! http://ferrarichat.com/forum/faq.php?faq=haas_articles Read the whole article, there is a piece about older engines and oil thickness. Pete

Yes, Oil DOES thicken when cold, but the 5W-x part suggests the two oils are similar viscosity when cold - a 0W-x thickens even less, a 10W-x thickens more, a 20W-x even more again as they cool.

As the oils heat to operating temperature, the flow differential narrows, so the xW-20 and xW-30 will have similar flows.

The problems come along when the oil cools - example: 5W-30 and SAE 30 are the same at operating temps, but if it's cooler (like a cold start), the SAE 30 thickens a LOT more, and provides less protection, as oil pressure increases, and flow decreases - it can't flow to where it's needed.

The second number tells the hot viscosity measurement. The 20 part says it thins more than a xW-30 which in turns more than xW-50 when hot.

The W is for "winter" and this first number ONLY specifies viscosity range at 40C (cold).

The second number ONLY specifies the viscosity range at 100C (hot).

The two numbers are unrelated to each other.

If SAE 30 is what Henry specified for your climate etc, then the ultimate oil to reduce wear is 0W-30, as it's the closest you'll get to a contsant viscosity, which is GOOD for the engine!

Ideally, you'd have an oil that has the same viscosity cold and hot, but all oils thicken somewhat on cooling.

Remember that multi-vis was NOT invented until the Model A was well over 20 years old, so Henry didn't specify it (actually, he couldn't!)

People say a certain oil is too thin, but thin is GOOD, to a point - too thick reduces flow and it can squeeze out of bearings before it is replaced sufficiently. That oil like water is what is protecting your engine - as it cools and gets thicker, it's protecting less and less (which is why so much wear happens on cold starts - thick oil!).

HIGH oil pressure can also be bad, as it means there is a restriction after the pressure measurement point, and the oil pressure gauge does NOT measure the pressure at the bearings, it measures it at the pump, BEFORE the restriction that stops it flowing to the bearings.

It's the Film strength that protects the bearings, not the pressure.

Ideally, the engine will run with an oil temp of close to 100C (212F), and that is the temperature that the oils are at "operating temperature".

Those people who "feel" an oil, and it's thickness out of the bottle, are forgetting an engine isn't in a happy place at room temperature, and neither is the oil - their ideal environment is WAY hotter than any room temperature a Human would be happy in!

Instead of using the SAE ratings as they are now, they'd used the viscosity range measurements (cSt - centistokes), the numbers would be easier to understand, and more meaningful:

The ratings would convert something like:
SAE avg cSt range "(cold)W-(hot)"

SAE 30 = 100W-12 (!)
20W-30 = 55W-12
10W-30 = 25W-12
5W-30 = 18W-12
0W-30 = 14W-12 <<< most consistant viscosity

And the 12cSt is "ideal" for an engine "designed" for SAE30 originally, which also has is viscosity of 12 at operating temp, shown on the top line, along with all the other oils with a SAE30 "hot" rating.

Other examples:
20W-40 = 55W-15
15W-50 = 40W-19
SAE40 = 150W-15 (!)

Rating it this way would give people a much better understanding of which oils are thicker cold or hot etc, and if explained with the principles of engine operating conditions would let people be much better informed about oil, and avoid all the confusion!

[Jacksonlll]

Use it, that A engine does not care what you use as long as it is slippery and clean.

[prpmmp]

Originally Posted by Allanw

Yes, Oil DOES thicken when cold, but the 5W-x part suggests the two oils are similar viscosity when cold - a 0W-x thickens even less, a 10W-x thickens more, a 20W-x even more again as they cool.

As the oils heat to operating temperature, the flow differential narrows, so the xW-20 and xW-30 will have similar flows.

The problems come along when the oil cools - example: 5W-30 and SAE 30 are the same at operating temps, but if it's cooler (like a cold start), the SAE 30 thickens a LOT more, and provides less protection, as oil pressure increases, and flow decreases - it can't flow to where it's needed.

The second number tells the hot viscosity measurement. The 20 part says it thins more than a xW-30 which in turns more than xW-50 when hot.

The W is for "winter" and this first number ONLY specifies viscosity range at 40C (cold).

The second number ONLY specifies the viscosity range at 100C (hot).

The two numbers are unrelated to each other.

If SAE 30 is what Henry specified for your climate etc, then the ultimate oil to reduce wear is 0W-30, as it's the closest you'll get to a contsant viscosity, which is GOOD for the engine!

Ideally, you'd have an oil that has the same viscosity cold and hot, but all oils thicken somewhat on cooling.

Remember that multi-vis was NOT invented until the Model A was well over 20 years old, so Henry didn't specify it (actually, he couldn't!)

People say a certain oil is too thin, but thin is GOOD, to a point - too thick reduces flow and it can squeeze out of bearings before it is replaced sufficiently. That oil like water is what is protecting your engine - as it cools and gets thicker, it's protecting less and less (which is why so much wear happens on cold starts - thick oil!).

HIGH oil pressure can also be bad, as it means there is a restriction after the pressure measurement point, and the oil pressure gauge does NOT measure the pressure at the bearings, it measures it at the pump, BEFORE the restriction that stops it flowing to the bearings.

It's the Film strength that protects the bearings, not the pressure.

Ideally, the engine will run with an oil temp of close to 100C (212F), and that is the temperature that the oils are at "operating temperature".

Those people who "feel" an oil, and it's thickness out of the bottle, are forgetting an engine isn't in a happy place at room temperature, and neither is the oil - their ideal environment is WAY hotter than any room temperature a Human would be happy in!

Instead of using the SAE ratings as they are now, they'd used the viscosity range measurements (cSt - centistokes), the numbers would be easier to understand, and more meaningful:

The ratings would convert something like:
SAE avg cSt range "(cold)W-(hot)"

SAE 30 = 100W-12 (!)
20W-30 = 55W-12
10W-30 = 25W-12
5W-30 = 18W-12
0W-30 = 14W-12 <<< most consistant viscosity

And the 12cSt is "ideal" for an engine "designed" for SAE30 originally, which also has is viscosity of 12 at operating temp, shown on the top line, along with all the other oils with a SAE30 "hot" rating.

Other examples:
20W-40 = 55W-15
15W-50 = 40W-19
SAE40 = 150W-15 (!)

Rating it this way would give people a much better understanding of which oils are thicker cold or hot etc, and if explained with the principles of engine operating conditions would let people be much better informed about oil, and avoid all the confusion!

Thank you Allan! Thats what I thought! You explain it very well!! Pete

[prpmmp]

Originally Posted by Jacksonlll

Use it, that A engine does not care what you use as long as it is slippery and clean.

X2 Pete