I usually add my educated opinion in other peoples threads, or to help or clarify an issue from the factory perspective.
There is this question about the proper fuel to use. My local Sunoco station pumps 60,000 gallons of High Octane fuel a month. A Corvette can use all the octane it can get, especially in the summer. it is much better to use a little more octane and be safe, than it is to use a little less octane and run the risk of detonation and premature engine failure. Those who think or claim they have no issues with low octane fuel are in denial. They just don't know any better and they are ( in the face o Factory design engineering advice )just being cheap and trying to goad as many people into their own cheap mentality about proper maintenance and care, these are the same people that buy 15,000 mile oil and keep it in there for 15,000 miles and they don't care id the oil has the specific heat shielding additive required in a Y body LSX engine which is a bottom feeder and runs a higher run temperature standard... Even your gut has to tell you that there is something wrong with using low grade fuel in a high performance engine. So please don't feed your LSX engine with lawn mower fuel.
Bill aka ET

 

Thanks ET. I never run anything below premium but wish I had some higher octane available around here.

You say the LS1 can use all it can get. Is there such a thing as too high an octane rating for this engine that is available retail?

 

Right on.... I always use the highest octane I can find in mine where ever I may be on the road or at home. Oil is another thing too. I'm still old school when it comes to that. I change it around 5-7K miles or once a year. Which ever comes first. My DD I use regular oil and change it every 3-4K miles.

 

These are the kind of issues that make me terrified to ever buy another used car. Our receptionist at work recently told me that her oil pressure gauge isn't working, so she waits to hear a knocking noise and then knows it's time to put more oil in...

 

I'm right there with you ET. I use 93 Octane (with 10% ethanol - all you can get in my part of Texas) from either Chevron or Texaco so I also receive the benefits of the Techron in the fuel. Regardless of where I am I won't use anything less than 91 octane.

As far as my oil goes, I use the regular Mobil 1 and change it when the indicator reaches 20-25% life remaining.

 

Is she blonde? She sounds a lot like my ex.

Quote:

"It still runs so the oil must be ok. I think I'll buy more shoes instead..."

 

Being an engineer also and with 50 years of automotive experience I know he is correct.

I have some cars with high compression and no "detonation electronics" that require I blend in racing gas to prevent detonation. It is hard to hear with exhaust and engine noise. My aged hearing is not what it was. I have used younger people like my daughter who can hear to confirm there is not any detonation going on.

Don't rely on electronics to prevent detonation. Use proven engineering on octane requirements to save your engine and wallet.

 

What kind of denial am I in? Can you run low octane? Yes. Should you? If at all possible no.

Don't think I don't know about preignition and detonation and what it can do to the cylinder walls.

 

ET:

First, it has been good to have you back on the Forum!

I know you have a lot of insider knowledge about our C5's and appreciate your willingness to share it...I also know the rigorous testing and validating done by GM engineering...so your input isn't just an educated guess...it is based upon established data/facts.

I have always used the best fuel and oil I can find for my collector cars. Probably costs me $100 - $200 extra bucks a year vs. buying cheap gas and using cheap oil w/long change intervals. Money well spent IMO.

You mentioned Sunoco...I know my local Sunoco is about the only place to find pure gasoline (no garbage ethanol in it) around here, but it is only rated at 90 or 91 octane (can't remember which). So, I have continued to use Mobil or Shell 93 octane - I believe both of which contain 10% ethanol (used to be able to KNOW that here in MI, but the green lobby got the law that required those labels at the pump repealed years ago - to protect the guilty - so now we don't know WHAT we are buying).

Anyway, I have always assumed the higher octane was the better choice, even given the ethanol content.

Would you agree?

 

The same people who cheap on gas will cheap on tires. I never understood that.

 

Iirc, 93 octane with 10% ethanol is the equivalent of 91 octane.

 

Kevin as an overseer in this forum for 13 years its easy to see those members who are seeking the cheapest brakes, the cheapest rotors, and the cheapest every thing. When this C5 forum was established, I use to, at times, get more than 50 Pm's a day, sometimes spending ten hours a day here to answer them all. Back then, members where looking for the best solutions not the cheapest. Dave Hill had a vision of a 200,000 mile bench marketed engine, that's what he wanted and that's what we delivered. its was the First 200,000 mile benchmarked and certified engine in the industry, prior to the LSX design the industry standard was tested to 100,000 miles. Just some insider stuff you may find interesting.
Bill

 

the only downside of too much octane is the loss of horse power because octane robs HP as an additive. but without it the engine will not reach its full potential. Ideally, the lowest octane that will not produce detonation ever will give you the most performance. But I would trade longevity anytime. if you use too little octane the engine will not reach its potential output, retard the spark and you instantly loose Hp and fuel economy. I use 93 octane, its 5 cents more than 91 octane. I may not need 93 octane all the time, but when I do need it, I want it to be there. Driving conditions change all the time. Select the wrong gear when going around a corner and engage a hill, anytime you inadvertently put the car under load, the demand goes up. Its like if you are running on foot (jogging), and then you turn onto a street with a hill, and you put a finger over one nostril, that's what detuning your car under load and retarding the spark advance does to your out put. This demand under load causes ping if you do not have enough octane. Ill take too much octane over not enough octane any day.
Bill aka ET

 

Great info. Thanks!

 

I finally found a station here that sells ethanol free 91. I'm pumped. I can't find anything above 91 here.

 

Thanks for posting this...

 

My brain doesn't even go there............that is using 87 octane fuel in my Corvettes. Honestly if it came down to me having to use 87 octane to save a few pennies I would sell the Vette first!

 

Some people hang on to the notion that using 87/89 octane in an emergency gives you the right to use it all the time, because it says so in the manual. The only reason that is there is to tell the idiots that your car wont blow up if you use it to get you to a station with better fuel. The problem we at GM and every design engineer I know no matter who they work for says : that we have to make it idiot proof .. You have seen some of those very Idiots we often talk about right here in this forum. You know the ones who see max tire pressure 65 psi on the sidewall and pump it up to 65 psi because it says so, or those who say 87/89 octane is ok to use all the time. You can believe them, you know the carpenters and the bankers and the construction workers and the brain surgeons and the postal workers.,
There are also some very savvy carpenters, bankers, construction workers, brain surgeons and postal workers here on this forum who's opinion I respect . I've been doing this for forty years, its not my hobby, and I don't go to a brain surgeons forum to tell them how to tap some ganglia. You do not have to be a brain surgeon to see the logic in my push back to those who think using 89 octane is ok, because it says so on the sidewall or in the manual. I know the analogy of the side wall and the manual is way above their pay grade. At times if some of the people who post in this forum were light bulbs, the forum would be very dark.
Bill

 

Wow you are not cynical at all. I apologize for all the idiots on here that don't have your level of education and rely on the teachings of said engineers that write the manuals for us to try and comprehend what you try to convey in said manuals.

For me being in the tire industry, when I see someone saying I put the tire pressure that was written on the sidewall, I don't call them an idiot. I politely explain to them to look at the door placard and use that pressure so long as you have the same tire dimension that is on the placard. I understand not everyone has my knowledge and accommodate accordingly. Not saying that it doesn't get tiresome repeating myself day in and day out. But it comes with the territory.

 

I'm more interested in the impact of the new 10% ethanol blends.

The car appears designed to run on 91 octane with no ethanol if I'm not mistaken. Given that many of us can no longer buy ethanol-free gas, should we now be doing anything differently to deal with the ethanol?

I just run 93 with 10% ethanol at all times and hope it will be OK at this point.