Ok, it was my first time to fill up the tank. I don't know how I did this. I was on auto pilot ... I put unleaded instead of premium in the tank of the C8 2023 Stingray. I feel like such a stupid bonehead! After I finished, I was like, HOLY COW... what did I do?

Do I need to go drain the gas? Or will it be fine and I don't do it again. And just drive slow until its all gone.

I can't believe I did that.

 

you'll be fine....the car will adjust to the lower octane......it may not perform at peak but it will be just fine.....drive it and when you get down half tank top off with 93 if you are worried...1 tank won't kill it

 

Im still kicking myself for this. LOL. Thanks. I was thinking, just drive it slow, until it gets to half, then fill with premium and then do that when it gets to half again, and then let it get to 1/4 and do it again. I have a long trip (2.5 hours each way) to show my dad the car, so Ill just drive slow and hopefully use up most of the gas. It was at 1/4 tank when i filled it up.
I can't tell you how silly I feel for doing that.

 

Just to be safe until I can refill when it hits 1/4 tank (doing that a couple of times). Should I add and octane booster to help. Its a C8, so I can't find much information on it since its so new.
I do NOT want to mess up my brand new engine.

 

no seriously it’s fine. Octane booster isn’t needed. The ECU will adjust timing to compensate for the lower octane fuel

 

What was the octane rating of the fuel that you put in the tank? 91 is listed in the 2023 manual. In any case, I would not add any sort of octane booster. They may contain substances that are harmful to the engine. And I would not drain the tank. I would add some premium fuel to the tank later. I checked the owners manual, expecting to find a statement about not adding anything to the fuel. Instead, I found this statement about additives - but it only applies if using non-TopTier fuel - and only periodically - and has nothing to do with octane. There is also a caution about lower octane fuel. Does not say that it will be catastrophic.

 

Just drive it!

 

The main thing is to not put the engine under heavy load. If you leave it in drive and don't floor it, you should be fine.

Having it manually in 8th at 700 RPM and flooring it would not be ideal. Also, not sure the transmission wouldn't downshift anyway, to protect the engine from lugging. While it seems that in manual mode you can select any gear you want, at any time, that is not true, it will still try to protect the car if you do something stupid.

 

thank you everyone. Im just going to drive it slow and top off at every 1/4 tank with premium.

 

It’s fine, I have done that a few times. Get a bottle of octane boost. And when it gets to 1/2 tank fill it up with 93

 

If you decide to use octane booster use Torco or Octanium.... Those are the ones that really work....

 

I will not add any fuel additive to my car other than what is recommended in the Owner's Manual. Some additives contain substances that can damage the engine. There is warning in the OM about fuels that can damage the engine and the substances that do so. One of those substances is methylcyclopentadienyl manganese tricarbonyl (MMT), According to the Safety Data Sheet (SDS) for Octane Boost, it contains methylcyclopentadienyl manganese tricarbonyl (MMT) which is listed under prohibited fuels in the OM.

The product "Octane Boost" is recommended by the manufacturer "high performance racing and off road use", and "collector automobiles, older off-road equipment and pleasure vehicles".

Owners Manual Warning:




Substance in Octane Boost from the Safety Data Sheet:

 

Based on the manufacturer's advertising, VP Octanium Unleaded contains MMT which is one of the substances listed under Prohibited Fuels in the Owner's Manual. The manufacturer appears to say that it is "safe" for emissions systems and catalytic converters when using the "safe blending ratio" provided in the "recommended mixing chart" that is provided. Use your own judgment if you choose to add this to your tank.

 

Yeah... the MMT does cause orange deposits on the plugs.... It takes a decent amount of use before that happens though.

 

Good idea! BUT don't lug the engine. Be sure rpm is in the 2000 range before using more throttle.

The posters who said you'll be fine are wrong! Read the Owner's Manual for the C8 and download the C7!

Yep for the C7 it was acceptable not recommend to use 87 octane if stuck in a foreign country! 87 octane is what regular is around here! With essentially the same engine and 40 more hp GM has pushed the air/fuel mixture and timing as far as they can! The ECU has no room to adjust anything more! That is old poor advice from folks who say you'll be OK! The manual clearly says:
Recommended Fuel
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.

Suggestions:
My Director of Marketing Communications bought a car with a turbo 4-cylinder engine because he got a good deal! Was upset when he found it required 93 octane high test gas! He said he was not going to do that! Good freind so some of the things I recommend to him were:

If going up a hill don't just use more throttle, shift down a gear and go to a higher rpm before using more throttle. When under load at low rpm is a sure way to cause knock. AND in the C8 you may not hear it as it has many knock sensorics BUT if you do hear it knock you know the ECU MAP had pulled all the timing it can and richened the fuel/air mixture all it can. Don't want a burned valve!

Same when cursing on the highway. For the C8, I would not use 8th gear or V4, use Manual Mode until you get at least half a tank used then add 93 octane. I would do than with 3/4 tank BUT still stay in Manual Mode and use 6th! Heck 4th, 5th, 6th, 7th and 8th are ALL overdrive gears! The higher gears and V4 are to help GM get the best possible mpg with the EPA test cycle. You don't have to use them all!

Yep, know someone will say the 2023 manual says you won't loss hp with 91 BUT that could just be GM wanting to keep folks in CA etc where they can olly get 91! Car is designed for 93 octane!

Drive properly for a half tank, fill with 93 Octane and you should be OK. Yep I'd mix with 93 octane at 3/4 tank as well BUT keep in manual Mode until a full 1/2 tanks fill of 93! Might find you like it and only go back to "automatic" when you get a full tank of 93 octane!

 

On my treadmill and had another thought. If it happened to me would drive as I suggested for 1/4 tank in Manual Mode, max 5th gear and the fill with 100+ octane racing gas! Several places around here sell it in 5 gallon jugs. If you have a civil aviation airport close, can get 100+ octane there or ask around.

 

Yes, it says, clearly, damage may occur if you use fuel with octane below 91. While the 2023 manual did drop the statement about losing power with 91 instead of 93, it says 91 is required, but in the section for tracking and competitive driving, it says that 93 is required. I don't believe that is a typo or mistake. I believe it still implies that the car can adjust to take advantage of 93 octane. I also agree with you that the statement about "damage" implies that it will not adjust well for octane below 91. As for what the car is "designed for", I would have said it designed to operate on fuel with octane between 91 and 93. Above 93, it is not stated whether it gets any additional benefit.

 

^^^^
Yep if I were GM might say that BUT if 93 is "required" for tracking - that is what they designed the C8 to run with! They have to include 91 as that all that is available in some States. Makes me feel even more that the elimination of 91 octane reducing power is just GM marketing so folks in CA don't go to bed upset!

SIDEBAR
Could be a tech reason when tracking as the car runs hotter. Recall my most recent experience with my S-10 V6 where I used a hypotrich programmer and had choices of several power levels. The max (which I used,) recommended 160 degree thermostat. Only issue I had was in the winter it vocationally tripped an engine CEL! I just plugged in my OBD tool and erased. Lasted a while!

Funny reason I added that programmer. Had a prior S-10 and when we moved I liked driving in on I95 to work versus using my Vette. So bought a new one with every HD option offered including quick steering, HD shocks, springs, posi etc. GM spec sheet showed ~30 more hp than my prior V6. But when I got it, the acceleration off the line was poor compared to my prior car! I was having to accelerate away from the Stop sign at the end of my street to merge into ~70 mph traffic (as I do now) and was having to slip the clutch and use a lot of throttle! The Service Manager at the Chevy dealer was a drag racer. He drove it and said, yep they used a higher rpm cam, so 30 more hp at higher rpm and lost low end torque! He said folks with automatic's don't notice the low end loss! If I were you I'd buy a Hypertech programmer! It worked! Richened the mixture and advance the timing. Also gave a bigger short of fuel when I mashed the Throttle! Used my G-TEC Pro accelerometer and measured the significant 0 to 60 mph difference! Remined me of adding 50 CC accelerator pumps to the Holley 850 carb in my Street Rod!

Recall when I built my '41 Coupe some friends had newer cars and we were always adding cams, carbs. headers, dif gears etc. We pushed the timing as far as Sunoco 260 would allow! That was 105 octane as I recall. If you heard a knock had to back off the timing! No knock sensors only your ears and had to listen carefully past the sound from the Cherry Bomb mufflers! Would not think of using 11.5:1 compressions as in the LT2!

And as you note, once you have sufficient octane to avoid knock, more is not useful!

 

I wouldn’t use any booster with MMT. It works very well, but it leaves orange deposits on everything from the spark-plugs to the tailpipe. It shortens the life tremendously of the catalytic converters and the O2 sensors.

 

Drive it slow alright but if you're down to 1/4 tank of fuel, just drive it until your down to say, 30 or so miles left on the fuel amount AND THEN fill it up and be done with it once and for all????? The gas that is still in tank at 1/4 full is still diluted to an octane lower than what's required. Remember, it's 1,500 miles what the C8 is broken in, not 500. Its's in the manual.
Good Luck