Gasoline Experiences?

[North of 49°]

I have noticed that when I use premium gas in the truck with the 3.5 Ecoboost, the engine does run smoother and I do get better gas mileage. The jury is still out whether the increased mileage is worth the extra 16% price I'm paying for the premium gas. The owner's manual (yes, I do RTFM (Read The Freakin' Manual)) says that under extreme conditions, which includes towing, that using premium gas may yield better performance and mileage. I haven't done enough testing yet; for just day-to-day driving, I put in the cheap stuff from a top-tier gas station.

But the main problem I have is that around the city, every station has 87, 89 and 91 octane, with the 91 being 0% ethanol and is considered premium. No problem, but once we get out in the boonies I can find only 87 at the Mom and Pop roadside stations. And when you need gas, you need gas -- I consider needing gas is when the gauge reads about half. Any less than that and I start panicking, unless we're close to home. So I have no choice but to get the cheap stuff from these questionable sources. I do feel better if the station has a logo from a recognizable gasoline company. But forget about getting premium!

[Hohenwald48]

Is octane rating related to ethanol content?

[RogerR]

Octane is basically a measure of how hot ( usually caused by high compression) that a fuel will ignite. If you have a high compression engine low octane fuel may pre-ignite before the spark plug fires. This causes lower mileage and loss of power.

Note that there have been a lot of stations caught selling regular as mid or high octane. Some have even had below octane regular.

I recently visited Denver where "regular" is only 85 octane. Most cars don't do well on it.

[Flapper]

Originally Posted by Hohenwald48

Is octane rating related to ethanol content?

Ethanol has an octane rating of 114, so adding it to gas can boost the overall octane number. Higher octanes are used to prevent pinging only, they don't have inherently more power/efficiency. Most modern cars can detect pinging, and then retard the timing a bit to compensate.
That noted, when towing, there is a lot more demand put on the engine, it runs hotter, and can be more prone to pinging. So running higher octane can reduce the change in timing, giving better fuel milage than with lower octane. But if the car/truck is already running at optimum timing, then higher octane is of no benefit.

On my Ecoboost, I can see a 5-10% milage improvement when towing, but nothing when not. Since the price difference is usually more than 10% higher, I only get premium to get me 5-10% greater range before having to fill again.

[RPreeb]

Originally Posted by RogerR

Octane is basically a measure of how hot ( usually caused by high compression) that a fuel will ignite. If you have a high compression engine low octane fuel may pre-ignite before the spark plug fires. This causes lower mileage and loss of power.

Note that there have been a lot of stations caught selling regular as mid or high octane. Some have even had below octane regular.

I recently visited Denver where "regular" is only 85 octane. Most cars don't do well on it.

This comment makes no sense. The octane is kept lower because of the altitude. I've been living in Colorado for 44 years and my vehicles have always run just fine on 85 octane. The only issue cars have in Denver is surviving the traffic congestion, which seems to indicate that the octane rating of the gasoline is no issue at all.

Back when I first moved here, most engines were still fed by carburetor rather than injected, and many needed high altitude jets to run properly. Most generators still recommend modifications for anything above 8000 feet. I don't know when they started using lower octane, or if they always have, but if it wasn't needed, they wouldn't make a special mix just for us.

It certainly doesn't have any effect on how well our cars run.

[robert9999]

I have used anything I can get pump into my 5.0 flex fuel Ford without any noticeable difference. It is wise to buy quality fuel though as some of the off brand names don't have the same detergent qualities that well known brands have ie: Shell, Mobile, etc. which will keep your engine running cleaner & better in the long haul.

[bansai]

I use 'regular' 85 octane here in Denver in all of my late model fords with zero problems.

I used to use premium in everything, but then watched this video - and did more of my own research.

https://www.youtube.com/watch?v=FPPkPAbzwbU

Now I run 'regular' 100% of the time when I'm in daily driving mode and use premium only when towing our camper.

[M&A]

Originally Posted by bansai

I use 'regular' 85 octane here in Denver in all of my late model fords with zero problems.

I used to use premium in everything, but then watched this video - and did more of my own research.

Now I run 'regular' 100% of the time when I'm in daily driving mode and use premium only when towing our camper.

Fun video. I run 13% dirty gas.