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I honestly don’t know if to run 87 gas or 91 I been using 91 does it increase my gas mileage and is it good for the car /VT
 

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research this forum as there is much content on this subject.
 

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I have a Rally '16 and I used 93Octane when I used to lived in GA. Now, I moved to Las Vegas and am using 91Octane from Sam's Club... GA Sams got 93 but here in Las Vegas they got 91Octane.
 

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I ran 87 in my car the first couple years, because the salseman said it was cool. 4 fuel injectors later and i only run 93octane now, 91 if 93nisnt available. I recommend sticking with 91 and above, not worth saving the few extra dollars a fill up when your car is in the shop
 

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9.5-10:1 is not high compression in relation to other cars from this era.

Welcome to the forum.
 

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I ran 87 in my car the first couple years, because the salseman said it was cool. 4 fuel injectors later and i only run 93octane now, 91 if 93nisnt available. I recommend sticking with 91 and above, not worth saving the few extra dollars a fill up when your car is in the shop
This would appear to imply 87 octane caused four fuel injector failures. Can you elaborate? This seems unlikely unless you were coincidentally running some very crappy cheap gas.
 

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I personally run Unleaded 88 aka E15. Running 91 or 93 octane is typically advisable in a turbo vehicle but it is important to understand more about the fuel you are running. There are actually a variety of ways the octane rating of a fuel can be bumped up to 91 or 93 and it is not always the same from one gas station to the next, even in the same region. Some people that swear by 93 octane might actually find that the fuel has a 93 octane rating because it is pumped up with ethanol while others might swear that their car runs like crap with 93 and it’s actually because of other additives in the fuel that bump up the rating. Still others may be seeing sweet performance gains by being fortunate enough to have fuel with minimal additives and plenty of genuine octane or heptane. Changing your driving style will make way more difference for gas mileage than fuel selection ever will, especially with these GDI engines. Driving it gently and staying out of Atkinson cycle can get me easily into the 33mpg average+ range.
 

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^^^^^This is pretty true^^^^^

Also E will lower fuel economy and if not tuned for the fuel it can actually lose power in some cases.

These cars from the oem is tuned to make more power and run best on higher octane lower E fuel. Lower octane and/or higher E fuels will not perform as well. The ecu is limited on how much it can adjust for octane and E content but can be ran on 87 in some cases or E fuels in some cases. Why hyundai said 87 is fine in these cars I'm not sure other than not trying to deter sales.
 

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^^^^^This is pretty true^^^^^

Also E will lower fuel economy and if not tuned for the fuel it can actually lose power in some cases.

These cars from the oem is tuned to make more power and run best on higher octane lower E fuel. Lower octane and/or higher E fuels will not perform as well. The ecu is limited on how much it can adjust for octane and E content but can be ran on 87 in some cases or E fuels in some cases. Why hyundai said 87 is fine in these cars I'm not sure other than not trying to deter sales.
Right. Addition of ethanol does one of two things depending on the bias of the ECU, especially in actual flex fuel vehicles. It will either improve performance by adding more fuel which results in lower fuel economy (which is how my ECU reacted by default) or it will hurt performance by not adding extra fuel and will result in maintaining about the same fuel economy or maybe a slight gain, but the economy benefit is mostly just that it is a cheaper fuel. This is the bias of a lot of Ford Flex Fuel vehicles, which is why a lot of Ford guys will tell you Flex Fuel is the worst thing ever meanwhile the Nissan guys find themselves doing accidental burnouts. Lol

I agree that Hyundai probably said 87 to not deter sales. It’s amazing how many people will say “oh, I gotta put premium in it??” and change their mind on a car. My old Ridgeline was kinda the same thing.Honda said it can use 87 but “it is recommended to use 89 or 91 for improved performance when towing”.
Using 87 wont really cause any harm, it’s just leaving power unused to save a few bucks.
 

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These cars can run on 87 but 91+ is recommended. Using lower octane in these cars can actually cause harm depending on the tune in the car and current mods and condition of the parts and the engine.

Also they run based on lambda. The way the oem tune is setup it will run by a set lambda value based on the conditions at any given time. The lambda is set for too rich afr for economy or power on pump gas with E0 much less higher E fuels. Higher E fuels will just make it run richer with lower economy and lower performance. Lower octane further reduces economy and performance. Thus higher octane and lower E the better and tune specific for a fuel type even better.

I tested a VT on the dyno using E30 on a 93E10 tune and it picked up power in the lower rpm but lost power in the upper rpm. Target lambda was .77 where E30 started losing power vs 93E10. This is too rich for best power on any fuel and is still much leaner than the oem tune targets.
 
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