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Turns out 'recommended' Premium gas doesn't do much

VegasStinger

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#1
Interesting article. This may even apply to the Kia Stinger since it's only recommended to use Premium. You'll give up a little bit of performance but for commuters this maybe something to think about.
http://money.cnn.com/2017/12/12/autos/aaa-premium-gas-study/index.html

On average, the vehicles got 2.7% better fuel economy when running Premium gas. But that's just an average. The results varied from a 7.1% improvement in the big Escalade SUV to a 1% decrease in fuel economy in the small Audi A3.

That means fuel savings are not enough to offset the cost difference between Regular and Premium gas.


AAA also looked at horsepower output. On average, vehicles produced 1.4% more horsepower using Premium. It made the biggest difference in the V8-powered Mustang GT, which generated 3.2% more power using Premium. But the Jeep Renegade actually produced slightly less power when running on Premium.
 
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#2
Another reason I like the Stinger. Premium is recommended in both the 2.0T and 3.3TT. You can use regular :)
 

TurboTx

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#3
I personally wouldn't skip premium in a turbo. My current car, which thankfully goes bye-bye this Saturday, is tuned for both but loses SO much power on regular it could get smoked by a civic. I think the deficit is like 10-13%.

I doubt the stinger GT will be seriously affected by using regular, even if it's a 10% drop you're still putting down over 300 hp, but a drop that big in the base Stinger would put you in the low 200s. That's a lot of weight for 200+ hp to pull around.
 

KiaFan

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#4
I agree with [MENTION=48]TurboTx[/MENTION], to me the gas savings is not worth the power loss even if it's minimal. Would be interesting if someone did some dyno pulls with both gas.
 

Stingin' Away

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I have only noticed a significant difference when it comes to cold starts. 87 causes choppy idle (not the good kind) and its rough. 91 is the highest we have in Rapid and it makes a noticeable difference on startup. My "butt" dyno can't tell the difference WOT and I think there is a slight increase in MPG. It's worth the extra 30 cents or so for premium. I like peace-of-mind.
 
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#6
My recollection is that most modern engines can detect the octane of the gas being used and adjust the engine's timing accordingly. I believe that to accommodate lower octane fuel, the engine's timing is retarded to prevent pinging and this reduces the engine's power output.
 
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#7
My recollection is that most modern engines can detect the octane of the gas being used and adjust the engine's timing accordingly. I believe that to accommodate lower octane fuel, the engine's timing is retarded to prevent pinging and this reduces the engine's power output.
Very true. You won't get full horse power or efficiency but the engine will adjust itself.
 
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#8
With today's high compression, direct injection, forced induction engines I would stay with premium. My F150 with the Ecoboost runs so much better with 93 vs. 87. It will run on 87 but there's a noticeable difference in performance, fuel economy and in smoothness, especially at idle.
 

cobrajet7

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#9
I'd do 91 in summer and 87 in winter. Summers are 105 plus

Sent from my Pixel 2 XL using Tapatalk
 
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#10
Right, it's not about fuel economy nor fuel efficiency. It's about how the engine was designed and the ECU tuned.

OEMs know some people will put anything that vaguely smells like gas in the tank so they try to protect the engines. Some do it better than others. Too low of octane for a particular engine (note that "too low" is a dynamic thing - depends on a huge variety of factors including the combustion chamber pressure (which is much higher with FI engines) and temp at each moment, spark plug temp, exhaust valve temp, etc etc) will result in the ECU retarding timing. Some handle this more gracefully than others. E.g., my '02 Lincoln simply cannot pull enough timing to run reliably on <91 octane, so it'll have detonation which will destroy rod bearings.

Best case, the ECU pulls enough timing to prevent detonation. It'll constantly be in "Oh Shit" mode and you'll be leaving power on the table. Worst case, the ECU can't keep up with the changing dynamics and you end up with rough running, detonation, and unhappy endings.

The good news is the Stinger ECU is super agressive about adjusting timing. They actually use timing adjustment to modify power output - timing advance drops to about 0degrees during shifts to be nice to the trans. So it's likely to be just fine running on the cheapest of gas, but the ECU will likely mess up from time to time and try to get back to its baseline tune, realize the engine is rattling apart, and back off again. Especially when flooring it.

Note that detonation/ping is different than it was in the '70s. We relied on the "metal can of rattling marbles" sound to tune ignition curves, but by the time you hear the marbles the problem is already extremely bad. Modern systems use a knock sensor and apply rather advanced signal processing to it (it's literally a wound wire that vibrates) to determine when detonation occurs. Note that different ECUs have different signal processors and algorithms. Ford ECUs from the late 90's were awful at this, so most tuners turn off the factory knock sensors.
 

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