KenMathisHD

So I've been dealing with the panicking people of Texas going out and hoarding gas as soon as it gets in. And while it's been fine so far, it's rather irritating.
The stations near me are no longer getting in 93 octane in, just regular unleaded and occasionally diesel. Now if I were driving the truck I wouldn't care, but with the truck being down unless there's an emergency, I've been taking the Vette pretty much everywhere. Since I've owned her, I've always always filled up with 93 octane, but last night I used up the last of that tank and had to go out and get 87.

I know technically it's supposed to be able to run on 87, and driving her home I didn't notice anything too terribly different, but I'm concerned that with the mileage on her (just reached 140k), running 87 might not be the greatest idea. Do you think it's safe to run her on 87 until somebody down here gets 93 octane back in their pumps? And aside from immediately filling her with 93, what should I do after the fact to make sure she wasn't too badly affected by using the lower octane?

Silver85

I think you will be fine. Unless you are running a modified engine with higher compression.

pologreen1

Nope. It is a production car and is made to be put through typical human situations.

It also has a knock sensor so the computer will handle anything if it gets unstable. you won't even know if just daily driving.

Now if you fill up and have water in your gas that is another story right now down there.

drcook

There have been magazine articles on the addition of octane boosters, with results from a dyno showing that they work to a degree.

It probably wouldn't hurt to call your local parts store and see if they have any.

Here is an old one.

http://www.hotrod.com/articles/fuel-...ng-comparison/

vader86

No it won't hurt the car, the computer will pull timing out to adjust for it.

belairbrian

The manufacturer's recommendation of 91 octane is based on the higher compression ratio (10.5 to 1). So there is an increased risk of detonation. As noted already the computer can make adjustments to prevent this. It may resulted in some loss of performance which may or may not be noticeable. Hard acceleration could increase the risk of detonation so for now just drive with moderation.

C6_Racer_X

I wouldn't sweat it too much.

With lower grades of fuel, I would try to avoid full throttle, especially at lower revs. That's when detonation ("knocking") is worst.

I also wouldn't bother with any "octane booster." Nothing that comes in a pint bottle (or smaller) added to 20 gallons of fuel will raise the octane by anywhere near 4 full octane numbers (87->91). With that mix ratio, you'll be lucky to get a couple tenths.

QCVette

It shouldn't hurt it.

To avoid detonation, drive moderately instead of loading the motor.

The owner's manual states:
"Fuel
Use premium unleaded gasoline rated at 91 octane or higher. You may use middle grade or regular unleaded gasolines, but your vehicle may not accelerate as well."

So it says you can use regular (87), but performance may suffer.

In practice I had one '94 that I didn't notice any change between premium and regular, and I have a '95 that doesn't like regular.

Go ahead and try it. Just be observant and don't use heavy throttle till you get better gas.

MRPVette

I accidentally filled up a couple years ago with regular unleaded by accident and it ran like crap so I added some octane booster and it seemed to help.

toricred

Around here 89 is the highest that they sell. We are at about 7200 feet elevation. That wouldn't be a problem would it?

pologreen1

I repeat... It's a gm car. Nothing special. Just plastic and aluminum.

They are built to handle any everyday situation.

I'd bet money lots of cheap c4 folks use 87-89 gas and won't admit it.

These are not late 60's cars, they learned and made things more versatile.

aklim

That car does sound like a carbed thing and is 10.4 compression so I wouldn't make too much of it.

aklim

Gas dry seemed to help my winter beater too. Every time it ran bad, dump gas dry and it seemed to help. Here was what was happening. Every time I dumped the stuff in it, I had to pull over, purchase it and dump it in. A few times later, I happened to drop the keys and picked it up. Noticed that the cat was glowing cherry red. Didn't buy the gas dry, waited 10 minutes and lo and behold, it was fine again. Got home, cut the cat off and never needed any more gas dry.

Moral of the story, what we feel is deceptive.

aklim

I have in a pinch. Sometimes it is 87 or walk. I have seen higher knock counts on 87 but I have 10.8:1 compression. It feels about the same but the knock count is higher.

C6_Racer_X

At that high altitude, you've only got about 3/4 of the air that we have close to sea level. That effective lowers your compression ratio (or, looking at it another way, it's like running a restrictor in the intake that holds ~7 inches Hg of vacuum at full throttle).

Either way, you don't have the cylinder pressures at that altitude to cause detonation from compression with 89 octane fuel. You should be fine.

If you drive it to the coast (either coast), you'll want to use higher octane, premium gas when you're closer to sea level to get maximum performance and minimize potential engine damage from detonation/knock.

belairbrian

here in Alabama seeing outages of grades above 87. They are moving as much 87 as they can haul to keep pumps going for the evacuation (and soon recovery). I'm sure once things calm down the other grades will start moving again.