Race11

I own a 2009 C6 with 20,000 miles on it. I've always put premium gasoline in the tank. I'm about to start driving the car everyday and would like to know how much of a difference using regular unleaded gas (87 octane) instead of premium (93 octane), if any, does it have on the engine long term? I know it is said that any grade of gasoline is acceptable but I did wonder about any long term affects it may have. I drive it in Houston, TX. Anyone have an educated opinion?

Welker1

I wouldn't use anything less then 91 octane; from the User Manual:

Gasoline Octane
If your vehicle has the 6.0L V8 engine (VIN Code U),
use premium unleaded gasoline with a posted octane
rating of 91 or higher. You may also use regular
unleaded gasoline rated at 87 octane or higher, but
your vehicle’s acceleration may be slightly reduced,
and you may notice a slight audible knocking noise,
commonly referred to as spark knock. If the octane is
less than 87, you may notice a heavy knocking
noise when you drive. If this occurs, use a gasoline
rated at 87 octane or higher as soon as possible.
Otherwise, you might damage your engine. If you are
using gasoline rated at 87 octane or higher and you hear
heavy knocking, your engine needs service.
If your vehicle has the 7.0L V8 engine (VIN Code E),
use premium unleaded gasoline with a posted octane
rating of 91 or higher. For best performance, use
premium unleaded gasoline with a posted octane
rating of 93. In an emergency, you can use regular
unleaded gasoline with an octane rating of 87 or
higher. If 87 octane fuel is used, do not perform any
aggressive driving maneuvers such as wide open throttle
applications. You may also hear audible spark knock
during acceleration. Refill your tank with premium fuel
as soon as possible to avoid damaging your engine.
If you are using gasoline rated at 91 octane or
higher and you hear heavy knocking, your engine
needs service.

AORoads

"...If you are using gasoline rated at 87 octane or higher and you hear heavy knocking, your engine needs service. ..."

It seems to me that if I read between the lines, the car will run on 87, or less than 91 octane. But, the question is, for how long? Maybe for as long as you own the car. Or, maybe not.

And it seems there is a warning in the above statement which is to come in AFTER the engine makes a noise. It also seems to me there is an implied suggestion NOT to cause the engine to get to that point where you need to come in because of noises.

Maybe I'm reading too much into the above.

Vettemuscle1

fuel grade is 100% relative to your compression ratio and the tune on your car (ignition timing). it sounds like the factory car is fine on 87 if you don't drive real aggressively and dont get junk fuel. But if you do run 87 and you can actually hear the knock (detonation) then you need to up the octane of your fuel. Detonation isn't necessarily destructive but it's certainly not optimal.

Another thing about higher grade fuels at the "good" gas stations is they generally run additives that help keep stuff cleaner internally. I notice it on my R1 runs smoother and the exhaust tip doesn't get nearly as black as when I am forced to use off brand fuels or low octane.

go read this website itll tell you everything you what you need to know about detonation.

http://www.contactmagazine.com/Issue...ineBasics.html

BlindSpot

Ha, ha, yes, we all have an educated opinion....

It'll run on anything they sell today as gas - 87, 89, 91, 93. There are two spark advance tables built into the factory tune. The ECM will choose what it needs to run based on what you put in the tank...and it'll do that on it's own...just drive it....don't race it on 87... No diesel though....

Bruze

Unchecked detonation can put a hole in a piston.

I'm not sure why, when gas is as cheap as it's ever been, that someone wouldn't use the recommended fuel in a world-class sports car.

Vettemuscle1

extreme detonation can do some real damage but i would hope you'd realize how bad you're car is running at that point. light detonation cruising at 2k down the highway isnt putting holes in pistons.

96GS#007

....a difference of about $4.50 assuming you put 15 gallons in the tank. $117/year if you fill up every 2 weeks.

Sorry, but if money is that tight...time to look for a more fuel efficient car

BlindSpot

Ever hear of a knock sensor??

EVRose

I was just gonna say how many pennies will you save per tank? Is it really worth it?

BlindSpot

Good point, but this is 2016 ya know.

need-for-speed

If you use lower octane fuel, the ECM is going to dial the spark advance back which will reduce performance (and I suspect fuel economy as well).

Diminishing returns. Burn the premium.

need-for-speed

And that is what will tell the ECM to pull timing (thusly reducing performance and fuel economy) ........

BlindSpot

THIS^^^^^ Finally, a voice of reason^^^.

BTW, the factory program has two complete spark advance tables. The default is the higher advance. If someone runs 87 octane the ECM will react (quickly) to several cycles of the knock sensors. If the ECM spark advance correction is exceeding the threshold on the higher table, then it will switch to the lower advance table. The driver will never know...and never destroy his engine.

Bruze

I was responding to him, and I stand by what I said.

Mad*Max

use 91 octane

RagTop69

This is an idiotic discussion. The car is designed for premium fuel and is capable of using something less if necessary but is pretty ill advised if you're trying to save a buck or two. If you've got a Corvette and you are that worried about gas prices, you probably have the wrong car. Go buy a Prius. BTW, both premium and 87 octane (AKA regular) are unleaded.

Judge387

I'm with everyone else and agree I wouldn't use anything less than what is recommended... If you just baby the car and drive it like a Prius you can probly get away with it. Premium fuel is a higher octane. I'm going to Try to keep explanation as simple as possible here.... A higher octane means the fuel can handle more heat before it will self ignite. When you start hammering down on it. Your building more cylinder pressure. More cylinder pressure means more heat. That is where the lower octane fuel will give you problems, it doesn't have enough octane to handle the extra heat and can self ignite.
Hopefully that explanation isn't to vague.
A buddy of mine had a ford lightning.
His dad drove the truck more than he did. They were always arguing about what fuel they put in. My buddy would use only premium. His dad thought it was nonsense and would only fill up with regular (87 octane).
Over time the truck developed a slight miss.
They decided to do a tune up. When they pulled the plugs all 8 were starting to melt. One of them the electrode was completely gone. None of us had any clue how the truck was still running as good as it was. But using a lower grade fuel is definitely what caused the damage.

BlindSpot

no problem. What is detonation?

If you had it or suspected it, how did you control it in the old days?

Vette_DD

What does your owner's manual say to use?

Why would you use anything else?