Better gas mileage with different octane?

But is it noticeable enough to justify the higher cost of premium?

 

You still fail to acknowledge that the ecu ALSO knows what octane level its using and has set parameters to run that fuel at the correct timing that the software engineers already tested at when designing the truck.

At low elevation it cannot safely run less than 87 without risk of detonation because it cannot retard the timing any less. It is at the bottom of the curve. Because the barometric pressure is significantly lower when you’re up higher (less air to breathe, and you need air+fuel for combustion), it is perfectly happy to use 85 octane with a similar timing that sea level trucks will use for 87. If you put in 87 at high elevation, it will still run fine because it will advance the timing similarly to how it would for you if you put 89 in. It will be down on power either way, but that’s what you get for having less air in the cylinder.

The octane and engine timing balances out with lower pressure, which is literally what us elevation guys have been saying this whole time.

 

All this bickering about gas and octanes.
As long as you have corn juice in the gas ALL calculations are off the window. Want LEADed pure gas? All Pipers and Cessna use leaded gas (aviation fuel) since with the (commercial) gas would not take off...

 

I love these threads where posters think they are smarter than the guys who designed the vehicle....

 

So the article from the Denver post that you linked is wrong that the logic once used for older cars no longer applies to modern engines?

 

AVGAS does not really work correctly in old cars that require Leaded Fuels because the Vapor Pressure is different.

 

I'll fill up on premium before a snowstorm, figure it gets me a little more driving before i have to fill up, little less chance of getting stranded without gas. Pretty scientific, huh?