MECF_728x90_top

Collapse

Announcement

Collapse
See more
See less

fuel octane question

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • fuel octane question

    In the manual it recommends 93 octane gas, saying anything less could result in decreased performance, gas mileage, etc. In my area, I've only been able to find 92 octane. Is the new C8 engine ok with that? I used 92 in both of my C7s and didn't notice any adverse effects. Thanks.

  • #2
    In California, we only have 91 octane and I haven't heard of this causing issues in our Corvettes. Maybe a bit less HP with the slightly lower octane.

    Comment


    • #3
      Corvette motors run excellently on 91 octane. Most of the time in Oregon that is what we get. Never had an issue with any of my Corvette motors, nor have any of my friends for decades and decades.
      GBA Black; HTO Twilight/Tension interior; Z51 & Mag Ride; E60 lift; 5VM visible carbon fiber package; 5ZZ high wing; FA5 interior vis CF; ZZ3 engine appearance; 3LT; Q8T Spectra Gray Tridents; J6N Edge Red Calipers; SNG Edge Red Hashmarks; VQK Splash Guards; RCC Edge Red engine cover; VJR illuminated sill plates. Lifetime, annual contributors, and 22 year members of National Corvette Museum. Home is the beautiful Pacific Northwest.

      Comment


      • #4
        This is exactly what the manual says:

        Use premium unleaded gasoline meeting ASTM specification D4814 with a posted octane rating of 93 — (R+M)/2. If unavailable, unleaded gasoline with a posted octane rating of 91 may be used, but with reduced performance and fuel economy. If the octane is less than 91, the engine could be damaged and the repairs would not be covered by the vehicle warranty. If heavy knocking is heard when using gasoline rated at 93 octane, the engine needs service.

        So the way I read that is 91 is fine, but you may get “reduced performance and fuel economy.” Don’t use less than 91.

        Comment


        • #5
          I'm lucky... my local Costco has 93 premium - and also has the lowest price in town.
          Hoping for a 2021

          Comment


          • #6
            Or local Costco has the 93 octane as well. Always fresh. Filling their underground tanks twice a day! Their gasoline rated very high in every regard. Cheapest in town by far, and using your Costco credit card gets you another 4% off. At times, their premium is cheaper than regular at the big name stations! Add that up over a season of driving your Corvette and family cars! And i'm not saying this because i'm a big shareholder in Costco!!

            Comment


            • #7
              Every modern engine has knock sensors. They detect early signs of engine pre-ignition due to low octane and signal the ECU to retard timing to avoid knocking. Retarding the timing reduces peak power and fuel economy. But 91 octane fuel won't result in pre-ignition all the time - only under load, at high rpm, or high temps or under some combination. So much of the time the engine will run no differently on 91 than 93. But peak performance will likely be reduced a little.
              SunKissed, my 2015 2LT, 7MT, Black over Daytona Sunrise Orange Metallic, Stingray convertible (One of about 40)

              Purchased 5/2/2015,
              >36,000 miles

              Proud member of the Old Dominion Corvette Club. Check us out http://www.olddominioncorvetteclub.org

              Never grow up - It's a trap.

              Comment


              • #8
                Originally posted by Mr. Wonderful View Post
                I'm lucky... my local Costco has 93 premium - and also has the lowest price in town.
                That opens up a whole new can of worms. Now we have to discuss “Top Tier Fuels.” Is Costco gas labeled as “Top Tier”?

                From the manual:

                GM recommends the use of TOP TIER Detergent Gasoline to keep the engine clean, reduce engine deposits, and maintain optimal vehicle performance. Look for the TOP TIER Logo or see www.toptiergas.com for a list of TOP TIER Detergent Gasoline marketers and applicable countries.

                It’s just a “recommendation” but it seems this comes up whenever fuel is discussed. I don’t have a strong feeling either way. All of my GM vehicles recommend top tier gas. I’ve gone back and forth over the years. If it’s roughly the same cost I’ll buy top tier if it’s convenient, otherwise I usually buy whatever is cheapest. What’s the consensus among forum members? Always “Top Tier”, always cheapest, or whatever is most convenient with little regard to top tier or cost? Maybe someone could set up a poll thread, I have no idea how to do that.

                Comment


                • #9
                  Originally posted by 16falcon View Post

                  That opens up a whole new can of worms. Now we have to discuss “Top Tier Fuels.” Is Costco gas labeled as “Top Tier”?
                  Costco is "Top Tier"

                  https://www.toptiergas.com/licensed-brands/
                  Last edited by Milliwatt Rob; 09-01-2020, 09:23 AM.

                  Comment


                  • #10
                    Originally posted by Milliwatt Rob View Post
                    Good to know. We don’t have a Costco nearby so we use Sam’s Club, they are NOT Top Tier, neither is Walmart or Murphy USA but they are usually the cheapest. Which is why I’m always in a quandary of whether or not it is really that important. I noticed my daughters Ford Fusion Sport owner’s manual does not mention “Top Tier” gas at all.

                    Comment


                    • #11
                      Originally posted by purple pearl 98 View Post
                      Or local Costco has the 93 octane as well. Always fresh. Filling their underground tanks twice a day! Their gasoline rated very high in every regard. Cheapest in town by far, and using your Costco credit card gets you another 4% off.
                      I'm also a fan of Costco premium (Top Tier, low cost), but I use my PenFed credit card, which gets me 5% off all gas purchases.
                      My C8:
                      '20 Elkhart Lake Blue 2LT Coupe, Natural Interior, GT2 Two-Tone Seats, Performance Exhaust, Front Lift, Carbon Flash Wheels, Engine Appearance Package 2000 Status December 27, 2019; 3000 Status January 2, 2020; 3400 Status March 10, 2020;TPW March 16, 2020; Built June 4th, 2020; Delivery July 1, 2020

                      Current Vettes:
                      '68 Lemans Blue 327/350 Convertible
                      '91 Turquoise Convertible with Hardtop
                      '14 Lime Rock Green 2LT Convertible, Black Top, Kalahari, 7-Speed, Performance Exhaust

                      Comment


                      • #12
                        Originally posted by 16falcon View Post

                        Good to know. We don’t have a Costco nearby so we use Sam’s Club, they are NOT Top Tier, neither is Walmart or Murphy USA but they are usually the cheapest. Which is why I’m always in a quandary of whether or not it is really that important. I noticed my daughters Ford Fusion Sport owner’s manual does not mention “Top Tier” gas at all.
                        It is important, not only Top Tier, but also specific brands for a given vehicle. Fords with turbos and many Toyotas prefer Chevron because of the additive Techron. Shells 93 octane has more additives than its lower octane fuels.
                        I have always used these fuels, and with vehicles I've put over 200,000 miles on, never have I had fuel related problems such as injectors. Also a vehicle will get better milage and performance with a specific fuel over another.

                        Comment


                        • #13
                          No worries 91 is fine. Software adjusts the tune. Have been dealing with this issue for many years --- even in Texas part of the state is 91 the other 93. Worrying about nothing.

                          Comment


                          • #14
                            Top Tier and Dexos charge licensing fees. The licensors then recommend the use of the licensed products. As a cynic, I find some snake oil in all of this. GM also collects from ExxonMobil for endorsing Mobil 1

                            All gasoline sold in the USA must meet minimum EPA additive requirements. Top Tier supposedly exceeds the minimum, but by how much is not transparently obvious.

                            90% of the fuel I use is Shell, Mobil. or Irving, all high quality and reputable.

                            Comment


                            • #15
                              Originally posted by L79 View Post
                              In the manual it recommends 93 octane gas, saying anything less could result in decreased performance, gas mileage, etc. In my area, I've only been able to find 92 octane. Is the new C8 engine ok with that? I used 92 in both of my C7s and didn't notice any adverse effects. Thanks.
                              All I can find around here (Western MO)is 91 octane. But my local Quick Trip ( it is Top Tier gas ) has a couple of pumps that offer it in non-ethanol. So I use that when I can. I've been getting 23-25 MPG indicated on my trip computer, every drive cycle, so it can't be too bad. I think the ethanol they do sell there is less than 10%, I think I'm safe at that level of ethanol if the non-ethanol pumps are occupied. Likely to run into ethanol on a trip, usually less than 15%. I honestly don't know where I could find 93 octane around my area.

                              Comment

                              MECF_728x90_bottom

                              Collapse
                              Working...
                              X