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Wrong Gas! What will it do



Hey all...In my frantic state to find a gas station this evening, the reserve icon was staring at me, I accidently put regular gas in my '96 LT1! Thats right 87 octane!!!! Poor thing.;stupid
So I babied her home, even though some ricer was looking to run...dang I hate to miss an opportunity like that...but I had stomped a *ord Rustang GT earlier, so I was ok with missing the ricer. SO anyways, I babied her home. I didn't notice anything bad happening, no knocking, didn't feel like any lack of power, everything was just fine. I did stomp on it once to bring the RPM up under load to see if that had any effect and she just jumped at the opportunity to run. So I'm left with the notion that I had almost a dry tank (1 bar left on fuel gauge) and completely filled it with regular. Should I be concerned? Will I have a problem with fouling plugs, pre-detonation? Should I go buy a can of octane boost? Run half the tank down and then fill it back up with Premium, or all the way dry again?

Ain't gonna hurt a thing. We don't NEED the high octane stuff for a stock engine anyway. ;)

_ken :w
So what you're saying is I'm spending about 20 cents on the gallon more than I need too??? Oh please tell me we NEED premium!!!!!:(
Mike, do you really think the powers that be want us to buy the least expensive option, when we can spend more - for something we don't need? Just take a long look around us. ;)

The only time you should need a high-octane gasoline for your engine is if you modified it for more power, or otherwise boosted the compression ratio and you needed the higher octane to prevent detonation.

If you are still hesitant at putting regular in your tank, use the mid-grade and you'd still save some change. I myself always burn premium in the Vette, but the truck and the bike get a lower octane fuel. ;)

_ken :w
My understanding is that the compression ratio is the biggest factor in what octane gas you need. The LT1/4 engines have rather high compression ratios, so 91 octane or higher (depending on your altitude) is required.

However, the LT1/4 engines also have an anti-knock sensor that will detect knocking due to low octane gas and retard the timing to adjust for it, which will rob the car of hp.

So, I guess you could drive the car with regular or even mid grade gas, but if you want the top performance out of the car, youll need to run the premium stuff.

I think I saw that somewhere in the owner's manual too. That Premium is the PREFERED fuel, but mid-grade is ok with performance being degraded with mid-grade or regular. My biggest concern is shock to the engine. I know sometimes in high performance engines, changing something in the air/fuel mixture after the engine has been "accustmed" to it for some time, can be hazardous. Usually this is found with heavy modifications, water injection, stuff like that. I've heard of a water injected engine that ran great with the water injection, but when the guys water injection pump failed, the engine pretty much tore itself apart. This was due to the engine running on water injection since it was built (not designed for it, just running with it) and the thermal shock of not being cooled as much as normal, killed it. The guy said he never saw over heating or any other problems until it let loose. Well, thanks for the info. Since its got a full tank of regular, I guess I'll see what kind of mileage I get out of it and if I notice any degredation in performance. If not, I'll know that in a pinch I can use it without worry.
Stan, talk nice to her. Apologize and promise NEVER to do it again. She will forgive you. Do something nice for her, like a lube job or a nice coat of wax.:D
Off topic here, I got to take out a 2001 torch red convertable today. One nice ride and I just LOVE that 6 speed. I'm torn between one of the new ones and a ZR1, but I think the Z will win out. I DO like all the gadgets in the C5s though. HUD, the steering wheel that goes in and out automatically, dual zone climate control (wifey REALLY likes that), the fact that you don't have to climb over that foot high framerail. I don't like the 45k pricetag though.

A little info Drewser...Stan is my dad Vetterpilot. I'm Mike LT1Vettepilot. Just a little subtle difference in name there:cool
I cleaned her a up yesterday, still looking really good. Maybe I'll treat her to a wax today if the weather stays nice.
I'ld love to get a ZR1, but for the prices around here, I could pick up a C5, and just a little more would get me a Z06. Sooo...I think I'll wait a while longer. After all, I've only had this one for 2 months now!
Listen I run Reg anyway these engines aren't DOCH Turbo units here they are pushrod V8's that have been used for the last 60 years (whatever) You dont need to run that stuff your paying to high for your gas. On some of the Rod's Ive built we've done some Supercharged engines with 11:1 compression on those we like to run the high octane (sometimes with a little more boost).

Run a performance Ignition spark system and you never worry about losing power, or do some other little mod to gain more HP Long run you'll save more money and always get the same if not better Hp
Bad Dog!

Well the good news is that you won't burn up the top end..and it's not the end of the world.

Just drive her nice for a bit till the tank empties and fill er back up....

Pretend that 300 miles didn't happen.

Poor performance and mileage

Well today was the first time I've driven my baby around for an extend period of time with the tank of ...ewwww...regular gas in her. There is a definate drop in performance. Both in off the line acceleration, passing acceleration, and general all around feel of the car. There was also a drop in mileage, about 3/10s of a gallon in just the hour and a half of errands I ran today. No change in driving habits either. I'll let this tank run down to about empty again then fill her back up with the good stuff. Its gonna be a long couple of weeks...


Of course the pair of blondes that were flirting did manage to perk up my day.
Hey--I used to jump out of those! I took off 40 times and still don't know what it's like to land in one.
Just a little extra feedback, Ken: even an L-98 runs fine with regular. I've run mine about 50,000 miles on regular with no problems, just noticeably less power than with premium - but still more than most anything else on the road!
The knock sensor takes care of everything. If you don't hear spark "knock", it's not there. Sorry about the extra 20-cents per gallon!

BTW, the L-98 was set up to run with well over premium fuel, so if you get some race gas, you can get several more horsepower, since the knock sensor will allow much more advance.

At least according to Z.V., the GM exhaust engineer on the L-98 cars.
Aubrey is in Denton County, north-northeast of Ft. Worth. Quite a ways from San Antone - unfortunately.

And Ken: I knew you knew that, about the fuel octane ratings! :)
I inadvertently addressed my post to the wrong person.

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