Do blends of the same viscosity flow as well as full synthetics at low temps?

[cheesepuffs2]

Say you have two oils, one blend and one full syn, both are 5W-30 SP gasoline engine oils.

The ambient temp is below 5 degrees F. Cold start in the morning. Both of these oils are within the temp range for their viscosity, but does the full synthetic circulate through the oil galleries and up into the heads quicker than the blend can upon startup? Even though the viscosity rating is the same, does the synthetic have any advantage here due to it's presumed lower wax content, or no?

 

[oldhp]

Just a guess but one is gunna have a pour point about 5° lower than the other, -48° F vs -43°F. So at your 5° F there would not much, if any flow difference with a positive displacement oil pump.

 

[Jetronic]

flow is not a concern with those temperatures: it's only the engine rpm that changes flow. The oil pump will deliver a fixed amount of oil per revolution. What could change is how much power is needed to turn the oil pump, but those are quite small numbers.

Only when you drop below the winter rating, or the oil gets old and contaminated and doesn't meet it's winter rating anymore, does the flow drop. But before that happens, you are likely to get a no start condition.

 

[kschachn]

And “flow” just isn’t what’s important. As long as the pump can pump the oil will flow. This is indicated by the winter rating.

At -5 any oil with a 5W winter rating will be pumped.

 

[cheesepuffs2]

And “flow” just isn’t what’s important. As long as the pump can pump the oil will flow. This is indicated by the winter rating.

At -5 any oil with a 5W winter rating will be pumped.

Can you explain the nuance between flow and pumpability?

 

[zray1]

Just a guess but one is gunna have a pour point about 5° lower than the other, -48° F vs -43°F. So at your 5° F there would not much, if any flow difference with a positive displacement oil pump.

^^^^^ this nails it. A positive displacement oil pump it going to move the same amount of oil with each revolution of its gears. As long as the oil is present at the pumps intake port, it will move the same amount of oil anywhere in the engine whether it’s a blend or fully synthetic or canola oil. The pump doesn’t know the difference. Viscosity may make a difference on the stress put on the pump, but that’s about it.

Many just choose to ignore what a positive displacement oil pump does, and focus on some mythical ability one oil has over another oil to reach some part of the engine “sooner”.

Z