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I noticed recently that Kwik Star has covered up their Top tier Logos on the pumps. Come to find out, the additive that they use is unavailable and it might not be available till the end of the year before they start selling Top tier again. So now I'm in a quandary. The Shell station up the street appears to have Top Tier but it contains up to 10% Ethanol. I'm not a fan of Ethanol, but now I'm thinking Top Tier with Ethanol would be better than gas with no Ethanol that's not Top Tier. Comments? Recommendations??
 

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Ethanol won't hurt your C7. It was designed for ethanol fuel, and none of the fuel system components will be harmed. Even E15 won't hurt it. Also, the "up to 10%" generally refers to regular grade - premium is usually lower.

Top Tier doesn't make as big a difference with Direct Injection engines as it does with port injection, but I would still choose Top Tier with ethanol over the other alternative. It will help keep the fuel injectors and piston tops clean.
 

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Thanks for the reply. I guess I'm moving to ethanol. It does make me a bit nervous. Just recently, a local Shell hit the news because several people who had just got gas had their cars quit on them due to what they called phase separation. Basically, they got water instead of gas.
 

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I noticed recently that Kwik Star has covered up their Top tier Logos on the pumps. Come to find out, the additive that they use is unavailable and it might not be available till the end of the year before they start selling Top tier again. So now I'm in a quandary. The Shell station up the street appears to have Top Tier but it contains up to 10% Ethanol. I'm not a fan of Ethanol, but now I'm thinking Top Tier with Ethanol would be better than gas with no Ethanol that's not Top Tier. Comments? Recommendations??
I use premium with additives. I’m pretty sure all have ethanol. Some Sunoco stations have a super premium. Sunoco is not convenient to me so I mostly buy Shell and Chevron.
 

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Thanks for the reply. I guess I'm moving to ethanol. It does make me a bit nervous. Just recently, a local Shell hit the news because several people who had just got gas had their cars quit on them due to what they called phase separation. Basically, they got water instead of gas.
While phase separation is related to the ethanol in fuel, water in the gasoline can be a problem with any fuel. It happened long before they started putting ethanol in gasoline. Even before they took the lead out. And since water is heavier than gas, it settles to the bottom where it gets sucked up.

This is more a problem with poor station management than the type of fuel.
 

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There seems to be a lot of "I read somewhere.." or "a guy told me.." language concerning Corvettes and "required fuel". Let us be clear, first and foremost our Corvettes since 1996 are "OBD II" (On Board Diagnostics version 2) computer controlled systems. The OBD II system is a GM developed system that every car built and sold in USA is required to use. The priority of the OBD II engine management system is #1 tailpipe emissions, #2 mileage, and a distant #3 is performance. The very interesting fact is the extremely fast Baud Rate of the OBD II operating system develops the high horsepower, clean burning, and incredible horsepower that we all enjoy in our Corvettes. These are the same benefits that our Ford Guys are getting out of their Mustangs and the Dodge guys are getting from their Hemi Challengers. As far as fuel is concerned, all the OBD II controlled cars are built to get the best result with the fuel recommended by the manufacturer. A 3.6 liter direct injected V-6 found in many GM cars and SUV's are programmed to run on 87 octane 10% ethanol lead free fuel. These 6 cylinder engines deliver over 300 hp on a mere 220 cubic inches. Using 93 octane premium doesn't seem to have and noticeable benefit. On the other hand, our Corvettes produce the incredible 400 to 485 horsepower from a 365 to 376 cubic inch engine as well as great mileage and clean tailpipe emissions. The use of 91 octane non ethanol premium will not hurt the engine and may actually deliver more performance. Then there are the guys (and gals) that run 89 octane mid-grade and 87 octane regular in their C-5, C-6, and C-7 Corvettes. Regardless of the fuel being used, the OBD II computer system will alter the entire ignition and fuel delivery program to maintain the 3 priorities of emissions, mileage, and performance. However, you will notice an immediate lowering of power when you attempt to accelerate and your mileage numbers will be lower, but tailpipe emissions are maintained. You have paid a lot of money for your Corvette, but when the knock sensor is activated from a misfire under load, the engine timing is retarded 2 degrees and will continue to be retarded 2 degrees until the misfire or detonation of the injected fuel stops. The power drop off can be substantial. Any and all misfiring or,detonation must be addressed to maintain clean emissions as a #1 priority. Using anything less than premium grade fuel in a Corvette programmed for premium fuel is a false economy. The direct injected LT-1 is very sensitive to octane differences. I had used 91 octane Mobil Premium in our 2014 Corvette for over a year. At freeway speeds (70 to 75 mph) we typically got 29-31 mpg. I went to our Mobil station and filled up on their 91 Octane premium, but I was showing mileage in the 26 to 28 mpg range. I went back to the Mobil station the next day to meet with the owner. I confronted him with my findings and asked him if he had substituted mid-grade or regular for the premium? He became very agitated and insisted the fuel was ethanol free Mobil Premium. I told him I was very disappointed in him because I felt he was lying to me. I informed him that i would be calling the Dept of Agriculture (Wisconsin) and making a formal complaint. They would come out to his station and test his 3 grades of fuel. All fuels have a unique chemical "finger print" as well as very specific gravity readings. The State agency can determine the quality of motor fuels using the specifications provided by the oil companies. He was found guilty of selling mid-grade as premium and was fined by the state and ordered to sell real premium at mid grade prices. That is how sensitive our Corvettes are to octane, and to get the most bounce for the buck you should want to use high quality top tier premium in your Corvette.
 

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I read you can run 87 without any problems.
That is what it says in my 2019 owner's manual, and it is no problem. Gas mileage is very close if not identicle. If I was going to race it, I'd burn premium with or without ethanol. Costco has top tier premium 93 with ethanol 40-50 cents below market plus the business card discount.
 

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Well, what the manual actually says is this: "will reduce performance and fuel economy."

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The 2019 manual says" Unleaded gasoline with an octane rating of 87 CAN BE USED. Using an Octane level below 93 will lead to reduced acceleration and fuel economy." So, to maximize fuel economy and performance you use 93. It does not say do not use 87 or do not use 91. It does not say the use will result in an engine damaging knock. It does say (regardless of the fuel) if a knock becomes severe, fill the tank with 93 ASAP to attempt to eliminate the knock.
 

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I noticed recently that Kwik Star has covered up their Top tier Logos on the pumps. Come to find out, the additive that they use is unavailable and it might not be available till the end of the year before they start selling Top tier again. So now I'm in a quandary. The Shell station up the street appears to have Top Tier but it contains up to 10% Ethanol. I'm not a fan of Ethanol, but now I'm thinking Top Tier with Ethanol would be better than gas with no Ethanol that's not Top Tier. Comments? Recommendations??
Costco has top tier gas. Probably doesn’t make a difference around town
 

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In most cases, 93 octane premium has 10% ethanol and 91 octane premium has no ethanol. I have used both, and my Corvette does everything better on 91 non ethanol. BTW, I was in Europe, and Shell and BP stations are selling 97 and 98 octane premium. I can't imagine the performance boost we will get if Shell makes that fuel available here. There is zero ethanol in that european fuel, but it is about $12.00 a gallon in Finland with a lot of that price being their "Carbon Tax".
 

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In most cases, 93 octane premium has 10% ethanol and 91 octane premium has no ethanol. I have used both, and my Corvette does everything better on 91 non ethanol. BTW, I was in Europe, and Shell and BP stations are selling 97 and 98 octane premium. I can't imagine the performance boost we will get if Shell makes that fuel available here. There is zero ethanol in that european fuel, but it is about $12.00 a gallon in Finland with a lot of that price being their "Carbon Tax".
Octane is rated differently in Europe. There, it's Research Octane. Here it's the average of Research and Motor Octane. 98 there is about the same as 93 here, although there's no exact conversion, as each fuel can vary.

And is simply isn't true that 91 octane has no ethanol. That might be true where you are, but it definitely isn't true in most placces.
 

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Octane is rated differently in Europe. There, it's Research Octane. Here it's the average of Research and Motor Octane. 98 there is about the same as 93 here, although there's no exact conversion, as each fuel can vary.

And is simply isn't true that 91 octane has no ethanol. That might be true where you are, but it definitely isn't true in most placces.
Thank you for the information on European fuel. Here I thought we would eventually have something that would really make our Corvettes perform. In Wisconsin and S.E. Wi. in particular, all our fuel regardless of the brand comes out of a place in the Milwaukee area called Jones Island. The different additive packages and the ethanol is added at this massive distribution area. If a station owner wants 100% gasoline with zero ethanol added he can have it. Many fuel retailers advertise that they have "pure gasoline- no ethanol". When you have tried both types of major brand premium, the 100% no ethanol premium 91 octane comes out way ahead of the 10% ethanol premiums. It is very noticeable not only in Corvettes but also in Harley Davidsons. The ethanol raises the octane by 2 points, but the alcohol burns off much quicker. Ethanol is a sacred cow in the midwest, and we consider ourselves fortunate if we find 91 octane no ethanol premium. Being skeptical, I have personally witnessed the testing of advertised non ethanol premium, and true to their word, the fuel had absolutely no ethanol in it.
 

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Costco has top tier gas. Probably doesn’t make a difference around town
I filled up yesterday at Costco. $5.65 per gallon for 93. I never use 87 so I didn't look at the price but I think it was around $4.87. --Bob
 
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