85 vs 87 ethanol in Denver (Not E-85 but regular 85)

Been using 85 with no problems. Local Toyota service tech saw no concerns with 85. I've wondered what would happen if I went from Colorado east to Kansas and still had 85 in the tank at that lower elevation, fortunately I haven't had to drive to Kansas.

 

The car has no clue what U.S. state you are in, only the car's approximate elevation above sea level. Much of Wyoming, Montana, Utah, and New Mexico should handle 85 with no problem whatsoever.

 

Lucky you. Engine self-destructs at state line. In case if it doesn't you will not survive: fall asleep and die in horrible crash while looking for Wizard of Oz museum.

 

I had a recent trip from Denver to Omaha. I didn't think twice about the (85 octane) gas, and I had absolutely no problems.

 

..that's what I was thinking all along too

 

I drove to Colorado a few months ago - I swear the car got better mileage with 85 - but it was probably all the hills filling up the battery that got me such good mileage while I was there. I fueled up when I departed, and drove through Kansas. I didn't have any knocking issues with that tank.

 

That could be quite true if you are comparing to Philly/Lansdale where you are probably in the EPA Reformulated Gasoline region. RFG is basically lower energy content gasoline, so you could easily be getting better MPG outside of home. Here is map. Also octane is not a direct measure of energy content, so you could easily have a 85 octane with good energy content, especially in a non-RFG area.

Gasoline and Diesel Fuel Update

 

do what now? if I read between the lines correctly we are to use 87 or is it referring to E-87 and not plain everyday 87 in the C?

 

High altitude areas use 85 octane for physics reasons which escape me at the moment, octane requirements go down at higher altitude.

 

I live in SE Texas my elevation is about 325 ft. should I be using 87?

 

Yes 87 octane of course Denver is mile high 5280-ft so they get to use 85. You do not have a choice as there is only 87 in the TX pumps.

 

oh yeah 87 is the base octane for me. ok I'm going back to sleep now.

 

That is one factor. Another is local air density. 85 is sold only areas of low air density (i.e. high elevation), which produces less MPG-robbing air drag.

With traditional gasoline engines, the lower air pressure also reduces 'pumping loss', boosting MPG even more. But the Prius has already improved that through other means, so has less to gain at high elevation.

 

I should have added that according to a relative who was blending gasoline at a refinery several decades ago (before RFG), the lower octane grades often had a slightly higher energy content. Thus, as long as the engine was happy, the lowest octane would produce highest MPG.

But due to various other factors that generally remain unknown to consumers, such as other blending requirements, resource availability at the refineries, and different fuel batches being produced by different refineries at different times, this wasn't always true. And with more factors thrown in the mix today, results may be less predictable now.

 

Just a reminder, don't confuse Octane numbers with E- numbers. E85 means 85% Ethanol, which you must not use in regular engines not set up for it. Leave it for the FlexFuel rigs, which doesn't include any Prius to date. Most consumer gasoline is now E10 (10% Ethanol, 90% gasoline) or E0 (pure gas).

As Wjtracy mentioned, you won't find 85 Octane at fuel pumps in Texas. I usually see it in Montana, Wyoming, and Colorado. It is just fine while driving there, but don't take home any spare cans of it.

 

The manual for my 2015 Prius C states do not use Octane less than 87; the manual states up to E-15 is acceptable and do not use any gas higher than E15 and the gas cap actually has a picture of E85 with a red circle and line thru it means no E85

 

...fyi this thread is discussing the special case high altitudes where 85 octane Regular is used (equivalent to 87 at low altitude).

 

I had same experience. Denver was great city for the Prius C (better than Minneapolis). I chalked it up to the hills.

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