Regular Unleaded or Premium Unleaded?

[Pyrenees]

I use 87 or mix 87/89 at fill-ups in the cooler months. In the summer (which is May-October in NC) I run straight 93 since I tow a utility trailer to the dump and stuff.

 

[dstewart3ss]

Seems like there are opinions that support both sides of the coin here. But what about flip flopping fuels? Like this thread, I’m not sure what’s best for my truck yet (just got it). Any reason I should avoid switching back and forth between 87 and 91 or 93?

 

[Pskhaat]

...the percent of fuel evaporated generally increases in proportion to the amount of ethanol added to the base fuel
Science.

Wait, wait. Which side are you arguing? The quote above supports the decrease in boil temp with ethanol.

 

[gatormark91]

I'm the only one on this forum with a fuel temperature gauge and an ethanol percentage gauge. Pump gas 85 octane boils around 110F at 6000 ft MSL. 30% ethanol mix doesn't boil even at 125F and 10,000ft MSL. Sure I guess I could copy paste someone else's work but I'll leave that up to you I'm going to go wheel in the mountains instead.

That because the vapor pressure drops off BELOW gas at that high an ethanol percentage. Vapor pressures act totally differently at E10 level.

Wait, wait. Which side are you arguing? The quote above supports the decrease in boil temp with ethanol.

Yes, more ethanol = lower boiling temp, depending on concentration, until the ethanol percentage goes above about E40. Then the line for the boil temp of E0 and ethanol gas cross on the graph. At E10 level, the boil temp is lower than E0 gasoline.

 

[ramangain]

That because the vapor pressure drops off BELOW gas at that high an ethanol percentage. Vapor pressures act totally differently at E10 level.

Yes, more ethanol = lower boiling temp, depending on concentration, until the ethanol percentage goes above about E40. Then the line for the boil temp of E0 and ethanol gas cross on the graph. At E10 level, the boil temp is lower than E0 gasoline.
View attachment 2366566

As they say, cite the graph unless it is your own math (data)

 

[gatormark91]

As they say, cite the graph unless it is your own math (data)

Mea culpa, mea culpa.

Summertime, When the Living’s Easy | Article | EESI

www.eesi.org