Higher Octane to Lower Combustion Temperatures?

i don't think anyone will know the answer, but you'll doubtless get opinions of every color and stripe.

you should add your car info, btw

 

I think it will not burn completely and leave more build up over time.

 

I agree with bisco. There is no way of knowing for sure without scientific proof and I certainly don't have it.

 

The only thing I could find is this:
"In the combustion of aromatic hydrocarbons, the engine combustion-chamber temperature is substantially higher than that with isoparaffins. Of the aromatics that were studied, benzene gives the highest combustion temperature and m-xylene the lowest. "

In reformulated gasoline areas, aromatics level is set fairly low (eg; ~40%) by EPA, and is similar for all fuel grades; so we would probably not expect much differernce of octane rating.

In Missouri, you could be in reformulated gasoine area in St. Louie, or conventional blends outside of St. Louie. We might expect the conventional blends to have a little more aromatic content than RFG, and thus burn a little hotter. The conventional Premium could be even higher aromatics.

In summary, the best thing would be reformulated gasoline or conventional regular. However, this is very much speculation. I do not think we have any hope to have data that shows that fuel grade impacts Prius repair frequency.

https://www.afpm.org/uploadedFiles/Content/Our_Members/What_We_Make/Fuels/US-Gasoline-Requirements-Map%20Jan2018.pdf

 

I would think using an ethanol blend gasoline, generally 10%, would give you slightly lower combustion temperatures. This would also cause a slight, maybe 5%, lower gas mileage but also a cheaper price per gallon which balances out. Another possible benefit is that ethanol is an oxygenated fuel so maybe less carbon buildup in the EGR cooler.