'08 Vette

[Yelcamino]

Can anyone tell me if the '08 Vettes require 93 octane or can they safely run on 87? Thanks.

[Boesch]

If you're referring to the LS3, then yes they can run on 87 octane just like the LS2's. I don't run 87 in mine, but I do know quite a few people that do without any knocking. The computer makes the appropriate corrections. If you had to run 93 most people in CA would be in trouble...hard to find something over 91 out here.

[Boesch]

From the 08 Owners Manual located here:
https://www.mygmlink.com/pdf/go2content/manual/US/en/chevrolet/2008corvette.pdf

Gasoline Octane
If your vehicle has the 6.2L V8 engine (VIN Code W),
use premium unleaded gasoline with a posted
octane rating of 91 or higher. You can also use regular
unleaded gasoline rated at 87 octane or higher, but
your vehicle’s acceleration could be slightly reduced,
and you might notice a slight audible knocking
noise, commonly referred to as spark knock. If the
octane is less than 87, you might 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 could damage the engine. If
you are using gasoline rated at 87 octane or higher and
you hear heavy knocking, the engine needs service.

[Young Gun]

if possible, on a car like that, go with the highest octan rating you can, it will be worth it if you keep the car for a while

[Boesch]

if possible, on a car like that, go with the highest octan rating you can, it will be worth it if you keep the car for a while

Strongly agreed.

[Nine Ball]

I'm not really seeing the logic of spending $40K+ on a new Corvette and then trying to save $0.30 a gallon on gas. lol

[PleaseNoSteve]

Agreed - dont be cheap and screw up your vette. Do the right thing.

[Yelcamino]

Thanks for the info... btw, I don't own one, I was just curious.

[justanova]

I'm not really seeing the logic of spending $40K+ on a new Corvette and then trying to save $0.30 a gallon on gas. lol

exactly, at the BMW dealer I work at we constantly have people coming in with their 80K 7's and 5's with the v8 and complain of a rough idle wich is caused by an excessive buildup of carbon on the valves and pistons due to running 87 octane gas and then they get mad when we try to sell them a top engine decarb service. even though it says premium 91 octane fuel is required.

to put into perspective on a 25 gallon tank at 30 cents a gallon savings that is $7.50

[Bill Howell]

I run premium in mine. Not worth the risk to me to use regular.

[Fuelie Fan]

How do you correlate carbon buildup to low octane fuel?


exactly, at the BMW dealer I work at we constantly have people coming in with their 80K 7's and 5's with the v8 and complain of a rough idle wich is caused by an excessive buildup of carbon on the valves and pistons due to running 87 octane gas and then they get mad when we try to sell them a top engine decarb service. even though it says premium 91 octane fuel is required.

to put into perspective on a 25 gallon tank at 30 cents a gallon savings that is $7.50

[Young Gun]

How do you correlate carbon buildup to low octane fuel?

Im assuming hes talking about the fact that with 87 octane there is not as complete a combustion as 91 or 93 octane. Since gas is a hydrocarbon, when the reaction does not go as far to completetion with a lower octane gas, the hydrogen bonds break thus leaving unbonded carbon molecules which over time build up. We arent talking about whole chunks of coal, but when a residue builds up, your engine will get jacked up badddd. But again, this is me just throwing assumptions around.

[justanova]

Im assuming hes talking about the fact that with 87 octane there is not as complete a combustion as 91 or 93 octane. Since gas is a hydrocarbon, when the reaction does not go as far to completetion with a lower octane gas, the hydrogen bonds break thus leaving unbonded carbon molecules which over time build up. We arent talking about whole chunks of coal, but when a residue builds up, your engine will get jacked up badddd. But again, this is me just throwing assumptions around.

Sounds like a pretty good explanation to me, I am no engineer or anything but when our v8's that use "Valvetronic" (variable valve lift to control engine (not a throttle body) speed, any carbon buildup causes the engine to surge at idle, like a rolling idle. The fix that was devised by the bmw engineers to fix this idle problem has been using the top engine decarb (the stuff we use is re-labeled GM stuff) and surprisingly it works. We do on occasion get cars that the owners actually run the premium fuel that will do it but not usually with the "top tier" rated gasoline from QT,Chevron etc.... The cars we most commonly see with this problem are when the customer admits to using low grade 87 gas. sometimes if we catch it soon enough we tell the customers to switch to 91 gas from QT/Chevron and it will clear up without using the decarb procedure.

on another note, I have had some of these engines with enough carbon buildup on top of the piston that it was actually hitting the head causing the piston to rock in the bore and put the cyl. out-of-round and a bad knockin/piston slap was noticed at idle under load. needless to say that car got the engine replaced.

[Fuelie Fan]

I strongly question your use of the word "fact" in that statement


Im assuming hes talking about the fact that with 87 octane there is not as complete a combustion as 91 or 93 octane. Since gas is a hydrocarbon, when the reaction does not go as far to completetion with a lower octane gas, the hydrogen bonds break thus leaving unbonded carbon molecules which over time build up. We arent talking about whole chunks of coal, but when a residue builds up, your engine will get jacked up badddd. But again, this is me just throwing assumptions around.

[Fuelie Fan]

Quick searching found as many people postulating exactly the opposite: that high octane produced more carbon. I think the bigger problem is the cheap gas, and octane rating is not the culprit at all. The cheaper brands don't usually have as many additives as the higher brands, additives that perform such functions as preventing carbon buildup. Now, the same people shopping for cheap gas may ALSO be shopping low octane, and for the same reason (save money). But, chevron or mobil 87 may in fact produce less carbon buildup than say Valero's 91.

Here's a good read if you want to gain an understanding of (relatively, I think this article may be up to 10 years old) modern fuel formulations

http://www.faqs.org/faqs/autos/gasoline-faq/part1/




Sounds like a pretty good explanation to me, I am no engineer or anything but when our v8's that use "Valvetronic" (variable valve lift to control engine (not a throttle body) speed, any carbon buildup causes the engine to surge at idle, like a rolling idle. The fix that was devised by the bmw engineers to fix this idle problem has been using the top engine decarb (the stuff we use is re-labeled GM stuff) and surprisingly it works. We do on occasion get cars that the owners actually run the premium fuel that will do it but not usually with the "top tier" rated gasoline from QT,Chevron etc.... The cars we most commonly see with this problem are when the customer admits to using low grade 87 gas. sometimes if we catch it soon enough we tell the customers to switch to 91 gas from QT/Chevron and it will clear up without using the decarb procedure.

on another note, I have had some of these engines with enough carbon buildup on top of the piston that it was actually hitting the head causing the piston to rock in the bore and put the cyl. out-of-round and a bad knockin/piston slap was noticed at idle under load. needless to say that car got the engine replaced.

[70 Chevelle]

Octane ratings are a rating of the fuels traits not qualities. If you were to compare 87 octane and 91 octane from the same company, say Mobil for example, the 87 octane is NOT a crappy counterpart. The 87 octane fuel has a lower resistance to heat and pressure without a source of ignition. Cylinder heat and pressure are the only things that dictate your needed octane rating. Using 87 octane on an engine with 13:1 compression will cause the fuel to ignite long before the spark plug fires because the pressure and heat will cause it to ignite much like a diesel. This is where a higher octane fuel is needed to withstand the cylinder pressure. An engine with 9:1 compression can happily run on quality 87 it's entire life. The higher the octane number the more heat and pressure a fuel can withstand before bursting.