Why Recommend High Octane Gas In GDI (non - turbo) Engine ?

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741
Location
Miami Beach
I have never used high octane gas in any vehicle. None in the Caddies,Caprice,Impala,Town Car or Crown Vic. All V8's. Put between 200-300K miles on all of them. All ran perfectly fine on 87 Octane. I still get good gas mileage on my DI 5.3 Tahoe at 100K miles and my other half has a 2015 6.2 DI Escalade with 95K miles and is running just fine on 87 Octane.

For most people all they get is the Placebo Effect using high octane gas. But the oil companies will love you as you as flush out your wallet.

Now if I had a Corvette or a Maserati I would consider high octane gas.
 
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2,622
Location
MN
In the article they should have tested the F-150 5.0. My 2019 5.0 pings a little since it has a 12:1 compression ratio. They bumped it up when the went to the Port/Direct injection combo. Premium helps, but it is more expensive.
 
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11,691
Location
Illinois

This is a good read.
I would have liked to see the actual test temperatures. The closest we get to this info is, "We performed acceleration runs, 200-mile fuel-economy loops at 75 mph, and dynamometer pulls, running each vehicle on two different fuels and completely draining the tanks in between. The differences likely would have been exaggerated by extreme summer heat, which exacerbates engine knock, but we sniffed out differences even with the engines huffing cool midwestern spring air."
 
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5,762
Location
Da Swamp
I ran 93 in the BMW 3 Series, because the manual required at least 91. The Mercedes sedans I drove from '97 to '07 all required premium -- though at Denver's altitude, mid-grade worked fine and did not ping. Otherwise, always 87 in my cars. At one point I tried premium in the Park Avenue with the old-school 3.8L; the gas mileage went *down*. And while I saw a little more peppiness in the 2.4L Regal on premium, that and the tiny bump in gas mileage were not enough to convince me to switch.

The 3.6L in the LaCrosse has only 11.5:1 compression, about the same as the Regal did. Not enough to make me switch there, either.
 
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2,393
Location
Paradise of Florida
Its hard to justify spending $30k on a watch that tells the time. But, some do!
I usually don't use cost analysis for my decisions concerning fuel or maintenance intervals. I use what feels best.

Its a Hyundai. If you are happy with the performance on 87, then do so.
I am not happy about the summer performance on the 2.4GDI with the A/C on when its 80+F outside and there are a few carpoolers in the vehicle. Pulling away from a redlights/stopsigns with 87 required a heavy foot, and not so much of a dog with 91-93.

Problem with posted dyno testing article is none included a 2.4GDI Hyundai/Kia product.

Since some high compression engines use fuel/timing to address issues with knocking, no one has long term studied octane vs performance vs fuel dilution vs engine longevity. I'll wager that premium might be beneficial in the long run. But, most dispose of vehicles often so why bother?

And, consistency in dyno testing needs to be addressed. Things that I would want mentioned.... oil temperature, coolant temperature, transmission temperature, maybe even tire/diff temps.... I'd wager that there might just be 'more' to premium in 'some' engines. Also, were the vehicles left on the dyno for the fuel octane changes(different tank sources), or driven empty and refilled? Never can restrap on a dyno for any source of consistency.

On that Turbo Honda mentioned in the article, the one with 18.5psi boost into what compression ratio????? How much fuel do you think it needs to control detonation? Definitely no issues with fuel diluting the oil with that engine family!

I do miss old low rpm low power per size V8... never did worry about octane. My 1.4T VW has the same ~150hp as my 5.0 CrownVic. Guess which one runs on premium always and which one ran on regular always? Not even worth mentioning engines not even close to what is sold now.
 
Messages
286
Location
North Dakota
Both of my vehicles (one port and one direct injected) recommend premium. I run ethanol-free 91 (highest available here) in both 100% of the time. Why do I pay more for a couple extra ponies? Mostly because I consume barely over one tank of gas per vehicle per month, so it's really not a budget breaker. Additionally, if you own a vehicle that calls for premium and you struggle to pay for premium, you probably are living above your means by buying said car in the first place.
 
Messages
1,628
Location
Texas, USA
There was a TSB for my GMC (3.6 V6) a few years ago, basically to update the shift logic on the transmission to eliminate "chugging". It was shifting into 6th gear prematurely, and not downshifting when RPMs were appropriate to do so. It produced a constant, very audible pinging with steady throttle, on level ground, sounding as if the fuel wasn't of sufficient octane. You could eliminate it by manually downshifting to 5th, or stabbing it enough to make it downshift, but it would go right back to 6th afterward. I started running 93 octane in it, and the pinging stopped.

After I got the TSB done, I went back to 87 and the pinging has not returned. 93 made no other appreciable difference in the way it runs, or the gas mileage.
 
Messages
833
Location
GA
Wow.

Go one size higher on the jets and back off the timing 1/8 turn of the distributor.

Oh, wait... this car was made after 1977? :rolleyes:
 
Messages
15,981
Location
NE,Ohio
Various forum members state to use high (92) octane gas in a GDI in even a non - turbo engine . I have a Hyundai 2.4L non turbo GDI engine and have tried several tanks of high octane (92) gas in it : While the engine naturally has greater pep with the higher octane gas - my gas mileage is better with the 87 octane gas . Please explain the added benefit of using high octane gas in a GDI engine (i.e. less intake valve deposits , extended spark plug life , etc. ) ? Thanks in advance !

Can we get examples of this? Havent seen it here.
 
Messages
1,628
Location
Texas, USA
I ran a few tanks of '93 through my Forte Koup SX, and as much as I wanted to feel a difference, I didn't. It never knocked or pinged on '87, so I didn't bother with the added expense after that.
 

Ws6

Messages
3,905
Location
South Central US
All else being equal except the octane, it won’t any difference to deposits, spark plug life, or anything else. That being said, Top Tier>non-top tier, and some retailers do advertise their premium as having more detergents in their premium grade.

From the manual I saw online, they say “87 octane or higher” which hints at it being able to take advantage of the higher octane fuel. Will you notice a real world difference? Unlikely.
I tested my CX5, and 20-80mph pulls resulted in a difference of 0.2 seconds between 87 and 93 octane, FWIW. Also, one magazine tested the CX5 on regular 87 and premium 93, and noted that their instrumented testing of it showed no appreciable difference.

Something to consider is environment. If you heat soak the car in traffic in 110*F Texas, then that 93 octane may well give you half a second to 60 better. However, if you're at 2000ft DA, in 50*F weather, 87 may max out the timing, or near enough it doesn't matter.
 
Messages
2,502
Location
NJ
With the arrival of the 2.4L DIT in the Subaru Ascent and then in the Legacy and Outback, Subaru does not require 91 octane like it did in the 2.0L DIT and other engines. It does state "87 octane or higher".

When they were working on the Accessport reflash for the Ascent, Cobb Tuning stated:

"During development, we discovered that Subaru truly calibrated the ECU to use an 87 octane fuel and testing with higher octane fuel on the factory calibration did not impact the overall power of the engine, though it did clean up occasional minor knock events".

The owner's manual does state that some knock is normal. But with Costco's 93 octane costing the same for me as most brands 87, I run 93 when I fill up at Costco because I would like to clean up those minor knock events! :) I've owned turbocharged Subaru's for 18 years so it's a bit of a habit.
 
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