Regular or Premium

I am a new Explorer ST owner and wanted to know if using 87 vs. 91 octane degrades performance noticeably.

If you run your vehicle hard or tow, 91 is the way to go. If not, 87 is fine. It won't give you as much HP, but is isn't that big of a loss. Maybe a 10-15 HP loss.

Is somebody checked loses with dyno stand? I thought that car will adopt to fuel and has almost the same HP

Why get a ST and not use premium? I f you want to use regular grade fuel, purchase a model with a lesser engine that is rated for it.

No, it would adopt to it, but won't make as much. Don't know if there is a dyno specifically for the ST, but other vehicles have shown different results.
Because some of us want to save money and not wast it. The ST is shown it is able to take 87.

You right, Ford seviceman says to me that boost of engine lowered when using 87 against 91. Also he says, that 93 is get max boost and did not significantly increase mpg

It really doesn't help unless yout towing or extracting tenths of a second off quarter-mile time.

I agree. Where I'm at it's 90 cents a gallon more for premium 91 octane versus 87 octane. 93 octane is near impossible to find here.

Couldn’t you go middle of the road with 89?

We don't have that. Closest is E15/Unleaded 88 octane. Not sure how I feel about it and I haven't seen any reports from anyone using it.

Here, 93 on interstate trips, 87 on the eight-mile, twenty minute commute. Fuel-cost-per-mile is a bit better on 87. It got 26.4 on the interstate in July (avg 24.2). The commute is averaging a bit over 20.

93 all the time. Here it is about 50 cents a gallon difference. Normal fill up is about 10 gallons so about $5 difference. I won't go large on that drive thru next time and put it in the tank.

There are at least three other threads that address this, but for the most part you're arguing apples/oranges. The key thing to understand is that an open throttle high-load application is very different than a part throttle low-load operation. Here are my thoughts on the matter.

https://www.explorerst.org/threads/premium-gasoline.1512/post-54146

For those not willing to follow the link, unless the 87 blend has a lower BTU content, at PART-THROTTLE loads, there is no reason 93 will give you better fuel mileage.

No argument from me. Just stating why I use 87 Octane.
What are your thoughts on using E15/Unleaded 88 octane ?

I think it's all a bit of a crap shoot based on the variety of gasoline/ethanol content fuels, and their variability. For myself, if I were taking a long trip on an unmodified vehicle, I wouldn't worry about it. An 88/15 model would probably not give the best mileage. On the other hand, if you're looking to make the best times, then I'd probably go with a 93/10 fuel. If you're modified with a tune, I'd follow the advice of your tuner. There are just so many variables in fuel quality, learning adaptations, etc, it's very hard to give specific advice.

However, the days (if they ever existed) of perfect octane ratios at the pump are gone- as are the days of half-assed knock control. You're just not going to find your engine with overlapped rod bearings or piston holes unless something goes majorly wrong with the sensors.

We're back to a $0.20 difference at Costco. Last summer it was $0.50. Still, 87 is more than adequate for my commute. We were going on a road-trip to Pensacola to visit the NAS Pensacola Air Museum, but apparently the base is closed to taxpayers for a while. Even that journey would only use a tank of gas. Maybe the Plains Car Show in April?

I am a new owner as well and use 87 octane and dont notice any significant difference.

I realize this is an older thread, but I really have to wonder how many of those commenting here have real world experience with the Explorer ST on a daily basis. I see so many comments here stating that there's no difference in the fuel that you use unless you're towing and to just use 87 octane. As someone who has owned a 2020 Ford Explorer ST and put almost 100,000 mi on it, I can tell you there is a massive difference in the way the car will run depending on the fuel that you put in. When I purchased my Explorer it had only 11,000 miles. For the first couple weeks I used premium fuel whether 91 or 93 octane. Because there is a $1 per gallon difference between 87 octane and 91 or 93 octane I decided that I wanted to save a few dollars and started pumping 87 octane fuel. It did not matter if I got my fuel from Shell, Sunoco, Amoco, Exxon Mobil or murphy's- I found that using regular 87 octane fuel caused my ST to run very poorly. I am not just talking about less horsepower or less acceleration- I am talking about the car knocking and the engine hesitating substantially. In addition to the poor operating, I also found that my fuel mileage went down substantially- I lost approximately 2.5 MPG when I used regular fuel instead of premium fuel. I used regular fuel in my vehicle for approximately 3 weeks. You need to know and understand that I travel extensively for work and I drive my car approximately 1,500 to 2,000 mi every week. I use amsoil premium oil and change my oil every 5,000 miles. After 3 weeks of using regular fuel I switched back to premium fuel and within One tank of premium fuel My car was running notably smoother and by the end of my second fill up my fuel mileage had increased over 2 MPG. I am not a car guy and I am not a mechanic, but what I can give you is real experience after driving the same vehicle with regular fuel and premium fuel over a long duration with a vehicle that is in top mechanical condition. The fuel that I have used has either been regular 87 octane or premium fuel, I have never used mid-grade fuel so I can't comment on mid-grade fuel performance. Performance. I also do not use any kind of fuel additives and my vehicle is completely stock. This vehicle is my daily driver- I am not a performance fanatic and not looking for any special thrill, I just happened to find this vehicle at an incredible price when I was car shopping + because of my past experiences of owning a 2016 Ford Explorer Police Interceptor Utility and a 2017 Explorer Platinum I couldn't pass up on this ST.