Can a forced induction engine actually run safely on 87 octane?

[Cujet]

I run 87 in both the 3.5 and the 2.7 Ecoboost engines. They perform quite well on 87. There is no question they make more power on 93, and get a touch better MPG too, but the near $1 per gallon premium stations are now charging makes it economically silly. The direct injection event is timed to prevent detonation, and it's rare that I hear any form of knock.

On another note, the EB engines get the best MPG when using non ethanol fuel, by considerably more that the energy content of the fuel would indicate.

 

[Pew]

I run 87 in both the 3.5 and the 2.7 Ecoboost engines. They perform quite well on 87. There is no question they make more power on 93, and get a touch better MPG too, but the near $1 per gallon premium stations are now charging makes it economically silly. The direct injection event is timed to prevent detonation, and it's rare that I hear any form of knock.

I've come to the same conclusion as my 1.0L ecoboost too. It runs perfectly fine on 87 but I use 91/93 when I'm driving up/down mountains because of the long ascents where you can feel the car knock and pull a lot of timing.

 

[circuitsmith]

Why not just buy mid grade?

Because there is a big price jump from regular to mid, and small diff from mid to premium.
It's cheaper to do the mix.
Also, we typically get such a heat wave once or twice a year and it's convenient to fill with prem. from a half tank in advance.
Pre-COVID a tank of gas would last a month (don't drive to work), now it takes 2 months to burn half a tank.

 

[wtd]

The manual for the Focus ST says 87 is ok, but recommends premium for best performance. According to numbers, it loses 11hp using 87. I run 93, as I like to minimize knock sensor intervention. 93 octane, SN+ oil, and keeping rpms at 2500 or above during acceleration is my engine longevity plan.

The manual for my 2014 Mustang GT says something similar. I always use premium just to have all of the HP available but have had to use 87 occasionally on longer trips where the gas station didn't offer premium. I couldn't really tell the difference in power.

 

[tcp71]

I’m sitting in a campground 200miles from home through the Rockies typing this. I towed 7500lbs here on 87 octane in my ford 3.5 direct injection twin turbo. It ran like a scalded cat up those hills. Unless it’s required and the engine can’t adjust for it, 87 works fine.

 

[SZR48207]

I’m sitting in a campground 200miles from home through the Rockies typing this. I towed 7500lbs here on 87 octane in my ford 3.5 direct injection twin turbo. It ran like a scalded cat up those hills. Unless it’s required and the engine can’t adjust for it, 87 works fine.

But 87 octane used at higher elevations would be considered a "higher" octane since regular gas in those areas is 85 or 86 octane...

 

[MCompact]

This is akin to asking, "Can I run Mastercraft tires on my McLaren 720S?"
My answer would be the same: "Possibly, but why would you want to?"

 

[hardcore302]

I have a 138 hp Trax. I use 93 because I need all the hp I can get.

 

[wemay]

In 200k+ miles the Santa Fe Sport has only had a handful of 93 octane fills. The Passat 2.0T strictly gets 87 except for one time when I wanted to see if there was a difference. I've never noticed a difference. The current price gap:

Chevron, Shell, Marathon and Mobil
87= $2.09
93= $2.89

Wawa ethanol free 89 is $2.69

At 18 gallons in the Passat, that's a significant $14 difference for the 10% ethanol fuel. (It holds 18.5 gallons)

 

[TiGeo]

In 200k+ miles the Santa Fe Sport has only had a handful of 93 octane fills. The Passat 2.0T strictly gets 87 except for one time when I wanted to see if there was a difference. I've never noticed a difference. The current price gap:

Chevron, Shell, Marathon and Mobil
87= $2.09
93= $2.89

Wawa ethanol free 89 is $2.69

At 18 gallons in the Passat, that's a significant $14 difference for the 10% ethanol fuel. (It holds 18.5 gallons)

I noted premium last night was $1 more than regular at a particular Shell station here in the Richmond, VA area. It's not chump change if you don't need the extra octane. Costco has a much lower difference between them....only about $0.30/gal.

 

[berniedd]

But 87 octane used at higher elevations would be considered a "higher" octane since regular gas in those areas is 85 or 86 octane...

Pls note that tcp71's engine has twin turbos. Normally aspirated engines will work well with lower octane gas at high elevations. The thinner air in effect lowers the compression ratio, allowing the use of gas with less antiknock properties. This "advantage" disappears if the engine has a turbo- or supercharger, which forces more air into the combustion chambers (higher compression ratio, now needs high octane gas). Yet, he says he uses 87 octane gas with no problems.

 

[DGXR]

The manual for the Focus ST says 87 is ok, but recommends premium for best performance. According to numbers, it loses 11hp using 87. I run 93, as I like to minimize knock sensor intervention. 93 octane, SN+ oil, and keeping rpms at 2500 or above during acceleration is my engine longevity plan.

Someone correct me if I'm wrong here. It is my understanding that the knock sensors are working all the time regardless of the octane. The ECM is constantly pushing timing to the edge of detonation, and then the knock sensors tell it to pull back slightly. The difference is that high octane fuel allows the timing to be pushed further before detonation occurs, providing better performance.

 

[Dohc98vteC]

I only stick to top tier 93 in my turbo, the difference is night and day. The ecu will constantly pull timing if not.

 

[TiGeo]

Someone correct me if I'm wrong here. It is my understanding that the knock sensors are working all the time regardless of the octane. The ECM is constantly pushing timing to the edge of detonation, and then the knock sensors tell it to pull back slightly. The difference is that high octane fuel allows the timing to be pushed further before detonation occurs, providing better performance.

Bingo - getting some activity on your knock sensors and pulling some timing is v. normal - if folks logged their cars all the time they would be shocked. It's fine and the whole point of the modern ECU - it allows for optimization of things like fuel.

 

[TiGeo]

I only stick to top tier 93 in my turbo, the difference is night and day. The ecu will constantly pull timing if not.

You will likely get some timing pull even with 93.