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

[OppositeLocK]

Turbo cars used to always require premium fuel in the past. Now some owners manual specifically state it's okay to run 87 (with some stating that performance will be reduced). Even my WRX's OM states that which really surprised me.

Isn't high compression with low octane a bad idea all around? I thought that was a big reason for the fuel dilution Honda was experiencing in their turbo engines.

How can an EcoBoost 2.7 possibly be spec'd out to run under all operating conditions constantly on 87 octane, with only a minor HP loss, yet not have it be detrimental to its lifespan?

 

[2EHA]

Knock control

 

[92saturnsl2]

Advanced knock control and in many cases, direct injection.

 

[gregk24]

I run premium in our current Jetta 1.4 TSI, and primarily ran premium in our previous Jetta 1.8 TSI. I can't say I notice any difference vs 87 octane but I don't flog our cars. I like the added protection.

 

[Rmay635703]

Direct injection cools the charge while it affects timing.

In theory direct injection would allow a diesel cycle in a gas engine via late injection and high pressure

 

[LotI]

Yes

 

[JT20]

I think the turbos DO run better on the 89 and then again on the 93 if the ECU controls spark timing. They have some sort of programming that will let them run on 87 just less power.

It's more fun on 93 if the engine can take advantage of it.

 

[oldhp]

I'm sure the fuel and timing maps allow both 87 and 93. If you want to try something for fun.............throw some 100 octane street legal unleaded fuel in it. I'll bet that turbo will love that!!! Sunoco SS 100 for instance.

 

[OppositeLocK]

Advanced knock control and in many cases, direct injection.

But doesn't knock have to occur first for it to be controlled?

 

[tcp71]

Considering ford eco boost twin turbos are their best sellers in the F150 and many are bought for fleet use and never get anything except 87, it’s a non issue.

 

[Trav]

It depends on the engine, the ECM and the programming, some can handle it many others cannot. With port injection and high pressure turbo its generally not the best idea. If the manufacturer specs only premium fuel then 93 it is, dont second guess.

 

[SwampDweller]

Had a 2016 Fusion with the 1.5T, ran it for 4.5 years on 87 octane as daily driver. Great mileage and power for DD. Oil would get black as tar in under 4000 mi, OCI never went above that. Never any fuel smell in the oil though.

Now have a new Mustang 2.3 Ecoboost as wife's DD. Have tried 87 and 93 Shell fuel, for normal run around driving, I can't tell any difference. Did a couple of hundred mile road trips and mileage seemed very close with both. Last couple tanks have been 93 Shell, we don't drive it that much to worry about cost(retired).

 

[Gimpy1]

I think the turbos DO run better on the 89 and then again on the 93 if the ECU controls spark timing. They have some sort of programming that will let them run on 87 just less power.

It's more fun on 93 if the engine can take advantage of

But doesn't knock have to occur first for it to be controlled?

Yes, but the multiple knock sensors detect knock in miliseconds and with the speed of computers timing is pulled very quickly. OEM's also account for this by building a safety margin into the tune itself that's one of the reasons why cars has so many sensors, plus the computer (s) are sampling data at increadibly fast rates. When you start increasing boost, compression, or modifing the tune outside of the OEM specs and you don't know what you are doing is when you get into trouble.You CAN run 87 but if you want the most power use 93 or higher, especially if you like stepping on the loud pedal.

 

[Trav]

That is if the ECM can pull enough timing. It is true there are safeguards built in to modern engines but on some even slightly older cars it was not so reliable. Some even had a knob under the hood for power and economy, without this being set and too low an octane fuel used there could be problems.

If someone has a car that has premium fuel only right on the fuel gauge or fuel tank door then it is best not to second guess this, this is not a recommendation but a requirement.

If you see this don't do it.

If you have wording like this its probably ok. The best thing to do IMO is read the owners manual and follow it.

 

[4WD]

Turbo cars used to always require premium fuel in the past. Now some owners manual specifically state it's okay to run 87 (with some stating that performance will be reduced). Even my WRX's OM states that which really surprised me.

Isn't high compression with low octane a bad idea all around? I thought that was a big reason for the fuel dilution Honda was experiencing in their turbo engines.

How can an EcoBoost 2.7 possibly be spec'd out to run under all operating conditions constantly on 87 octane, with only a minor HP loss, yet not have it be detrimental to its lifespan?

I found some turbo engines liked mid grade ... and figure it’s both cheaper and fresher than premium

 

[TiGeo]

Sure, if the car says 87 is the min octane rating then you can run 87 safely all day. Maybe a better question is - what specifically do you think will fail pre-maturely doing this? Modern ECMs are so good...they just pull the timing back a little if needed. My Sportwagen ran happily on 87 before I tuned it; it runs on 93 now as that is what the tune is designed for but even then....it's not going to blow up if I ran a tank of 87 and drove it easy. APR produces an 87 octane tune for the VW MQB turbo 4 cars and they run safely/no issues I've read about. You lose out on a little top-end power is all and if you logged it, you would see the timing correction is the source.

 

[mightymousetech]

BMW turbo engines (well all engines) test the fuel every time you fill up, and will run a fuel/ignition map for the octane in the tank. The higher the octane, the more power and better FE you get. Fun fact, when we connect our factory scan tool, we can see exactly how many tanks of each octane has been used since new. Comes in very handy when people complain of rough running and lack of power.

“Sorry sir, you have used 32 tanks of low grade fuel, and only 1 tank of premium, and 0 premium+”

 

[WylieCoyote]

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.

 

[TiGeo]

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.

Exactly - if you don't want it to pull timing under hard acceleration/high engine load situations, run premium. If you are sitting on the highway for an hour a day with the CC on, why waste the money....I know here premium is a lot more per gal than reg. I still will always argue that the worry about timing correction with the turbo crowd is WAY over-thought and if people actually logged their cars regularly to watch things, they'd see that even with 93 they may get some timing correction from time to time...it's nothing to worry about and has no impact on the engine's longevity. I look at it this way, you can make the timing table for the ECM very conservative so you never see any correction, or, you can make it broader to allow for more advance and then you can gain more power when you run premium or ethanol blends. Final comment, I think people would be shocked at how much variability you get with fuel quality from tank to tank or station to station and if modern engines were that sensitive w/r to octane rating, people would be having all sorts of issues all the time but they don't....you never head about it b/c it doesn't happen. The ECMs have been designed well and there is plenty of room in them for fuel octane variability.

 

[MNgopher]

I have a 2016 F150 with the 2.7L Ecoboost. I run mainly 87 octane, but use premium when towing and when I am curious about differences in performance and what the engine perceives from the octane. Currently at 65,000 miles with zero issues. The owners manual calls out 87 as the required fuel, with premium recommended for maximum performance and towing.

In practice, one can monitor the Octane adjustment Ratio (OAR) to guage how the truck is reacting to the fuel it is being fed. It ranges from a 1 (Bad) to -1(Good) in Torque. In practice, I find that 87 octane typically puts me between .15 and -.2. In other words, right around the center of the expected range. The highest I've gotten was -0.93 running a Shell Premium 91 octane. Most 91 octane fuels (and even the 93 octane I've tried) ends up running around -0.7 to -0.8. (I will note I have a 36 gallon tank, so there is virtually always a residual of 4-7 gallons of fuel in the tank when I typically fill up)

What does all that mean? Note that the OAR has never been -1.0. The engine is always monitoring and adjusting timing in response to (gasp) knock, among other things... Even on premium. I chuckle when I read that I feed it premium to minimize knock - the engine management will keep trying to find that point and if the OAR isn't at -1.0, it is behaving just like it does on 87 octane - just with different timing, etc... that allows for more power. That's it.

So can an forced induction engine safely run on 87 octane? Emphatically yes - if it is designed to do so. The Ecoboosts in the F150 have been proving it for a long time in an enormous number of vehicles.