Here are results from some very crude relative viscosity tests of several engine oils at four different temperatures: 108F (heated), 68F (room temp), 41F (refrigerator temp), and -1F (freezer temp).
Comparative oil flow was observed and is listed in the order of greatest flow (lowest viscosity) to least flow (highest viscosity).
Not all oils were tested at each temperature.
I can make no guarantee as to the accuracy of my observations, but for what ever they’re worth, here they are.
Relative Flow at approx 108F (+ or – 8F):
Quaker State 5w-30 > (flow is greater than)...
Quaker State 10w-30 >
Mixture (90% Havoline 5w-20(SM/GF-4) + 10% Synpower Oil Treatment) >=
Mobil 1 0w-40 =
Quaker State 10w-40
Relative Flow at approx 68F (+ or – 5F):
Honda 0w-20 >=
Amsoil XL7500 5w-20 =
Exxon 5w-20 =
Havoline 5w-20(SM/GF-4) >
Mobil 1 0w-40 >=
Quaker State 5w-30 >=
Quaker State 10w-30 =
Mixture (90% Havoline 5w-20(SM/GF-4) + 10% Synpower Oil Treatment) >
Quaker State 10w-40 >
Syntec 5w-50 >
Synpower 20w-50
(Note: Syntec 5w-50 at 68F > Quaker State 5w-30 at 41F).
Relative Flow at approx 41F (+ or – 5F):
Honda 0w-20 >=
Amsoil XL7500 5w-20 >
Exxon 5w-20 >
Mobil 1 0w-40 >=
Chevron 5w-30(SM/GF-4) >=
Quaker State 5w-30(SM) =
Quaker State 5w-30 >
Quaker State 10w-30 =
Mixture (90% Havoline 5w-20(SM/GF-4) + 10% Synpower Oil Treatment) >=
Quaker State 10w-40 >
Syntec 5w-50 >=
Mobil 1 SS 15w-50 >=
Mobil 1 EP 15w-50 >
Synpower 20w-50
(Note: Synpower 20w-50 at 41F > Honda 0w-20 at -1F).
Relative Flow at approx -1F (+ or – 5F):
Honda 0w-20 >=
Amsoil XL7500 5w-20 >
Exxon 5w-20 >
Mobil 1 0w-40 >
Havoline 5w-20(SM/GF-4) >
Mixture (90% Havoline 5w-20(SM/GF-4) + 10% Synpower Oil Treatment) >=
Chevron 5w-30(SM/GF-4) >=
Quaker State 5w-30(SM) >
Syntec 5w-50 >=
Mobil 1 SS 15w-50 >=
Mobil 1 EP 15w-50 >
Synpower 20w-50 >
Quaker State 10w-40 >
Quaker State 5w-30* >=
Quaker State 10w-30*
*Note: Quaker State API SL 5w-30 and 10w-30 became very viscous (more viscous than the 10w-40) and somewhat gelatinous when left at -1F for several hours. This was unexpected.
Most oils tested were the previously rated API service SL or ILSAC GF-3. The newer conventional API SM and/or ILSAC GF-4 rated oils are noted as such.
Test Method:
Using a small syringe 2.0 cc of each oil was dispensed into a stoppered glass test tube. Oil was coated on the entire inner wall of each test tube before standing test tubes vertically and allowing oil to settle to bottom (about 5/8" deep) for several minutes at room temperature (approx 68F).
Samples were cooled in vertical position for one or more hours in freezer (-1F) or refrigerator (41F).
Samples were heated while standing near vertical in a small metal can. Heat was applied with a 100 watt light bulb for about 20 minutes until thermocouple placed in with the test tubes read a temp of about 115F.
Upon removal from low or high temp condition, samples were immediately compared to each other by quickly tilting the test tubes, in unison, from vertical to horizontal on a flat surface, side by side, to observe how fast and how far the oil spread out along the length of the test tube. The length of the oil puddles were compared over a period of roughly three to ten seconds.
A faster spreading (longer) puddle was considered to be the greater flowing (lower viscosity) of the oils being compared during each test.
Up to four samples were compared to each other during some tests. Usually just two samples were compared to each other per test.
Temperature of the cooled or heated oil was assumed to change too much to be meaningful if test samples were allowed to remain at room temp any longer than about 15 or 20 seconds.
The "greater than or equal to" (>=) symbol was used if the difference in spread towards the stopper end of the test tube was noticeable and usually repeatable but less than about 1/16” or 3/32" by eye.
Several of the close tests were repeated more than once to confirm observations.
Heated, room, refrigerator, and freezer air temperatures were measured with a thermocouple and digital display.
General Observations:
1. At low temperature, synthetic oils seemed to flow better than comparable rated viscosity API SL conventional oils. For example at -1F Synpower 20w-50 > (had greater flow than) QS 10w-40.
2. At moderate and elevated temperatures (~40F to 108F) synthetic and conventional oils of comparable viscosity ratings seemed to have roughly comparable flow.
Unexpected Results:
1. Mobil 1 0w-40 flowed better than conventional Havoline 5w-20(SM/GF-4) oil at -1F.
1. Mobil 1 0w-40 flowed better than conventional 5w-30 oils at -1F, 41F, and 68F.
2. The gelling of conventional API service SL Quaker State 5W-30 and 10w-30 at -1F was unexpected.
3. The newer API SM rated Quaker State 5w-30 flowed much better at low temperature (-1F) than the previous SL rated 5w-30 Quaker State oil.
4. The thickest oil (20w-50) flowed better at 41F than the thinnest oil (0w-20) at -1F.
5. The (90%/10%) mixture of Havoline 5w-20(SM) / Synpower Oil Treatment seemed to posses desirable properties since it flowed slightly better than conventional 5w-30(SM) oil at -1F, and yet exhibited a viscosity between 10w-30 and 10w-40 at approx 108F.
Final note:
These tests began with freezer comparison testing more than a year ago. I was curios if Syntec 5w-50 had been flowing well enough during some cold (5 degree F) startup conditions I had subjected my car to. I wanted to see if the manufacturers suggested oils (conventional 5w-30 and 10w-30) would flow any better at 5 degrees F.
I was also considering switching from Syntec 5w-50 to Mobil 1 15w-50 and wanted to compare their viscosities at low temperature as well.
Things grew from there as I conducted a few tests from time to time over the past year and a half or so.
Comparative oil flow was observed and is listed in the order of greatest flow (lowest viscosity) to least flow (highest viscosity).
Not all oils were tested at each temperature.
I can make no guarantee as to the accuracy of my observations, but for what ever they’re worth, here they are.
Relative Flow at approx 108F (+ or – 8F):
Quaker State 5w-30 > (flow is greater than)...
Quaker State 10w-30 >
Mixture (90% Havoline 5w-20(SM/GF-4) + 10% Synpower Oil Treatment) >=
Mobil 1 0w-40 =
Quaker State 10w-40
Relative Flow at approx 68F (+ or – 5F):
Honda 0w-20 >=
Amsoil XL7500 5w-20 =
Exxon 5w-20 =
Havoline 5w-20(SM/GF-4) >
Mobil 1 0w-40 >=
Quaker State 5w-30 >=
Quaker State 10w-30 =
Mixture (90% Havoline 5w-20(SM/GF-4) + 10% Synpower Oil Treatment) >
Quaker State 10w-40 >
Syntec 5w-50 >
Synpower 20w-50
(Note: Syntec 5w-50 at 68F > Quaker State 5w-30 at 41F).
Relative Flow at approx 41F (+ or – 5F):
Honda 0w-20 >=
Amsoil XL7500 5w-20 >
Exxon 5w-20 >
Mobil 1 0w-40 >=
Chevron 5w-30(SM/GF-4) >=
Quaker State 5w-30(SM) =
Quaker State 5w-30 >
Quaker State 10w-30 =
Mixture (90% Havoline 5w-20(SM/GF-4) + 10% Synpower Oil Treatment) >=
Quaker State 10w-40 >
Syntec 5w-50 >=
Mobil 1 SS 15w-50 >=
Mobil 1 EP 15w-50 >
Synpower 20w-50
(Note: Synpower 20w-50 at 41F > Honda 0w-20 at -1F).
Relative Flow at approx -1F (+ or – 5F):
Honda 0w-20 >=
Amsoil XL7500 5w-20 >
Exxon 5w-20 >
Mobil 1 0w-40 >
Havoline 5w-20(SM/GF-4) >
Mixture (90% Havoline 5w-20(SM/GF-4) + 10% Synpower Oil Treatment) >=
Chevron 5w-30(SM/GF-4) >=
Quaker State 5w-30(SM) >
Syntec 5w-50 >=
Mobil 1 SS 15w-50 >=
Mobil 1 EP 15w-50 >
Synpower 20w-50 >
Quaker State 10w-40 >
Quaker State 5w-30* >=
Quaker State 10w-30*
*Note: Quaker State API SL 5w-30 and 10w-30 became very viscous (more viscous than the 10w-40) and somewhat gelatinous when left at -1F for several hours. This was unexpected.
Most oils tested were the previously rated API service SL or ILSAC GF-3. The newer conventional API SM and/or ILSAC GF-4 rated oils are noted as such.
Test Method:
Using a small syringe 2.0 cc of each oil was dispensed into a stoppered glass test tube. Oil was coated on the entire inner wall of each test tube before standing test tubes vertically and allowing oil to settle to bottom (about 5/8" deep) for several minutes at room temperature (approx 68F).
Samples were cooled in vertical position for one or more hours in freezer (-1F) or refrigerator (41F).
Samples were heated while standing near vertical in a small metal can. Heat was applied with a 100 watt light bulb for about 20 minutes until thermocouple placed in with the test tubes read a temp of about 115F.
Upon removal from low or high temp condition, samples were immediately compared to each other by quickly tilting the test tubes, in unison, from vertical to horizontal on a flat surface, side by side, to observe how fast and how far the oil spread out along the length of the test tube. The length of the oil puddles were compared over a period of roughly three to ten seconds.
A faster spreading (longer) puddle was considered to be the greater flowing (lower viscosity) of the oils being compared during each test.
Up to four samples were compared to each other during some tests. Usually just two samples were compared to each other per test.
Temperature of the cooled or heated oil was assumed to change too much to be meaningful if test samples were allowed to remain at room temp any longer than about 15 or 20 seconds.
The "greater than or equal to" (>=) symbol was used if the difference in spread towards the stopper end of the test tube was noticeable and usually repeatable but less than about 1/16” or 3/32" by eye.
Several of the close tests were repeated more than once to confirm observations.
Heated, room, refrigerator, and freezer air temperatures were measured with a thermocouple and digital display.
General Observations:
1. At low temperature, synthetic oils seemed to flow better than comparable rated viscosity API SL conventional oils. For example at -1F Synpower 20w-50 > (had greater flow than) QS 10w-40.
2. At moderate and elevated temperatures (~40F to 108F) synthetic and conventional oils of comparable viscosity ratings seemed to have roughly comparable flow.
Unexpected Results:
1. Mobil 1 0w-40 flowed better than conventional Havoline 5w-20(SM/GF-4) oil at -1F.
1. Mobil 1 0w-40 flowed better than conventional 5w-30 oils at -1F, 41F, and 68F.
2. The gelling of conventional API service SL Quaker State 5W-30 and 10w-30 at -1F was unexpected.
3. The newer API SM rated Quaker State 5w-30 flowed much better at low temperature (-1F) than the previous SL rated 5w-30 Quaker State oil.
4. The thickest oil (20w-50) flowed better at 41F than the thinnest oil (0w-20) at -1F.
5. The (90%/10%) mixture of Havoline 5w-20(SM) / Synpower Oil Treatment seemed to posses desirable properties since it flowed slightly better than conventional 5w-30(SM) oil at -1F, and yet exhibited a viscosity between 10w-30 and 10w-40 at approx 108F.
Final note:
These tests began with freezer comparison testing more than a year ago. I was curios if Syntec 5w-50 had been flowing well enough during some cold (5 degree F) startup conditions I had subjected my car to. I wanted to see if the manufacturers suggested oils (conventional 5w-30 and 10w-30) would flow any better at 5 degrees F.
I was also considering switching from Syntec 5w-50 to Mobil 1 15w-50 and wanted to compare their viscosities at low temperature as well.
Things grew from there as I conducted a few tests from time to time over the past year and a half or so.