The only relevant thing that changed was the rating method in North America. What used to be called 98 under the old RON system was relabelled as 92 or 93 under the new AKI rating. Most people were unaware of this change over and believe that the actual octane level was reduced. Being that this change over was introduced about the same time as the crude heavy pollution controls on cars, reduced compression, and the first of the unleaded gasolines, the myth was created that 'gasoline in the good old days was better'.

Lead is gone but it's been replaced with far superior compounds that can equal or exceed any octane requirement that exists with far less toxic emissions.

 

 

BS, WHAT toxic emissions?? anyone ever REALLY have a health problem with it?? really?? NO, is the answer, age 68 here born in '44, entire world ran on leaded gas for decades around me, never an issue with me or any of my friends, Kalifornia is an unproven cause/effect on their air 'problems'....many other changes than just auto emissions out there,.....

they lowered compression, making engines less efficient, costing MPG and performance, increased CI size to make up for some of it, and fuel economy for any given size car was reduced about 30%, I know, I lived it....the only thing that saved fuel economy at all is electronics and the micro chip....nothing to do with fuel, except if we had TEL back in gasoline instead of Alky, we could all be getting an easy 30% more fuel economy....much less get rid of cat *** trophic converters...another expensive, useless item....

 

BS, by any method you measure they were cut a LOT, nearly ten points....engine pinged like mad, timing was reduced, compression knocked down to as lo a 8-1 and still ran like crap....

that period in the 60's when cars ran so easy and good was not replaced until the mid 80's due to electronics, all through the 70's that embargo farce and the Karter/Iran farce...and today, we spending over 10% extra for crude/gasoline than we need to....

 

Mrvette, you sound like a very angry and bitter person. I think if you informed yourself with some readily facts instead of repeating old myths (like octane falling 10 points) you'd enjoy life a little more. Perpetuating well thrashed war stories doesn't really help new owners that are simply trying to understand what actually changed between 'then' and 'now'. Jus' sayin'.

 

Typical liberal, don't like the truth, attack the messenger.....buddy, I lived through it, saw the cause/effect on my own cars, lack of timing, lack of power rebuild this and that, fight to get compression back up, rejet carbs so they run decently, and still had to fight for every mpg even with the improvements...

I"d love to see leaded gas come back, up our MPG a goodly amount, for sure....

 

Not sure that this thread answered my question or not. I just remember back in the day putting lower lead in my car made it ping and sputter and fuss. So now that I have gone and bought my 79' Vette was wondering what to run in it...regular? Premium? is there a difference today like there was back in the 70's? Does anyone use gas additives, and are they safe? Or have I opened another can of worms?

 

I think you are confusing Octane with Lead content. 2 different animals. Lead was used more as a lubricating agent that also allowed for octane increases whereas the Octane number itself is from refining a type of fuel that detonates under different conditions. The volatility of a fuel or octane is basically the pressure the fuel will take before it ignites spontaneously. (I know that is very simplified.) But pinging is the noise made by seperate flame fronts colliding in a cylinder, because predetonation occurred. There is a lot more to it, but the basic premise I have always heard is to use the lowest octane you can that does not ping or knock under any condition(not getting into the timing issues). If you use octane that is too high just to use it when it's not needed, carbon deposits can form, and thats not good. I hope I didn't spin that wrong. Someone will correct me if I did.

 

You and me are basically on the same side, the affects are reduced timing, making less power and lower compression doing the same thing, then pushing that crap through a cat *** trophic converter so it 'smells' good to some flower or whatever....

meantime for any given car weight, you lost a LOT in fuel economy, and that is the bottom line....

yeh, they made the converters less restrictive, supposedly....

but the OP's car being a '79 will get along fine on today's gasoline, I really don't think the ethanol will totally kill the thing....

but it kills your ability to tune for max MPG....

 

Ok Gotcha, thanks!

 

Sorta kinda. There's hundreds of ways to increase the octane rating of fuel by using additives- lead was the cheap, quick and dirty way of doing it but far from the only way. Today's gasoline has additives other than lead to achieve any desired octane rating from very low 80s (used in high altitude locations) to AKI of 105, 110 and higher. Very few cars need anything higher than 91-93 so that's what's commonly available.

Using fuel with higher than minimum required octane rating will cause no harm other than wasting money. It does not lead to carbon deposits or any other things that are commonly rumoured. The sole reason to use higher octane gas is to avoid detonation (not predetonation, no such thing).

Lead (TEL) had a side effect of coating combustion chamber components with a thin layer that acted to reduce valve seat erosion. This was never an issue on Corvettes so the elimination of lead in the 70s was the best thing that ever happened to avoid deposits.

For the OP- your owners manual will state what octane rating your car requires. As far as I know, it was built for regular (87) octane and will not benefit from anything higher.

mrvette has got lots of technical issues confused- too bad he resorts to name calling rather than learning.

 

mrvette - I don't usually get drawn into these types of discussions but are you really serious that you think burning lead in fuel didn't cause air pollution or heath issues or are you just trying to get a rise by making such a bizarre comment? Just doing basic minor investigation of this will show what effect lead has on people and our brain in particular. I won't get into the octane debate but to state that lead causes no harm to humans is just showing a complete disregard for facts that have been proven for decades.

Before you start, I also "lived through it" and have never been accused of being liberal - not that it has any merit on this as fact is still fact.

 

If the octane ratings weren't affected, then why did the auto companies drop the compression ratios in their engines when they started specifying "unleaded fuel only" in the mid-70s. Lower compression ratio affects the efficiency of the engine, fuel mileage, etc.

 

Because the imprecise carburetors, (aren't they all?) of the times would burn richer than necessary, combined with LO compression ratios meant less power per unit of fuel consumed, they had to drop comp ratios to burn the new crap fuel mandated by the feds....so MPG/EFFICIENCY fell through the floor....

GM seeing the writing on the wall, and much aware through DELCO division, of the modern chips, contracted out some engines to a Newport News company, BENDIX then bought by Allied Signal, then Siemens....

so it seems that BENDIX went to work with a Olds 350 Caddy 425 and supposedly a Caddy 500 ci engine to develop DPFI for electronic engine controls, not that typical pisser system from the daze of mechanical as in 60's vettes and VW bugs....

so it was all done with analogue electronics, things known as Op-Amps and various ways to use electronic sensors to measure engine temps and air temps, and even to do O2 sensor inputs (but I never seen one in production).....

The Caddy that used the Olds 350 engine was the fugly pudgy back Seville? in the late 70's the 425 system I pulled off a 425 along about '89 or so was off a '79 Sedan DeVille....I talked to one guy in NW regions of this country long time ago, he claimed to have a top end of a FI 500 cu. Caddy engine...but I never seen one, in spite of looking....

so Yeh, I know a bit about it all, enough to slay any green weenies, anyway.....

 

Your government mandated that all cars must be able to run on low octane unleaded gas, starting in 197X (I forget the year- 76?) AND be able to achieve stifling emission limits at the same. The only way of doing that was with low compression, conservative ignition, wimpy cammed crude tech convertered engines that produced only a shadow of their pre-smog equivalents. If today's technology and gasoline existed back then (mid 70s) nobody would have blinked but unleaded 93 was not available in the 70s.

mrvette, in his confusion, thinks that today's unleaded 93 is somehow inferior to yesterdays 93 with lead. Not true.

 

Alcohol contains LESS BTU's per gallon than gasoline- it takes MORE alcohol to heat a given amount of water to a specified temperature than the same amount of water heated to the same temperature with gas. With that, adding 10%, or very soon to be the government mandated 15% of alcohol to gas, you are going to reduce the emissions a tiny amount while using MORE to get the same distance.

 

You seem to be pushing your version of it as some kind of expert witness. "Acted to reduce valve seat erosion?" WTF? Okay, just so that we're on the same page, when they took the lead out of gasoline, the valves SLAMMED into the seats without the nice soft cushy leaded barrier...and HAMMERED the seats until they wouldn't seal. If that is "acting" to "reduce" valve seat "erosion," great...but it almost sounds as if over a million years of rain the side of a hill came down...and not 15-20K miles later, your seats were simply gone.

Nobody in the general public "expected it" as an outcome of removing the lead. However, bunches of cars suddenly needed repairs. I don't know anybody, even flaming liberals, who were cheering unleaded fuel back then.

How that was "never an issue on Corvettes" is beyond me. I don't know of any Corvette engines built before unleaded fuel that had hardened exhaust valve seats.

Maybe there are things that you *think* you know that you don't really know? However, the one truth that I can tell from leaded fuel is that it created a whole bunch of mad-as-hell flaming liberal environmentalist whack-jobs who have since ruined the USA. It is now more viable to build parts in CHINA or Mexico or ANYWHERE ELSE because everyone is so damned important that nothing else matters. It was probably the lead in the fuel that caused them to get so "crazy." Unfortunately, they've multiplied like a bad virile infection and have spread their brand of spew everywhere...the next thing they're going to tell us is that we have to pay a tax on the air that we breathe...oh wait, that's what Ethanol does...never mind. Go back to your regularly scheduled programming...you've been assimilated. (Which is kind of like *** and humiliated put together, if you think about it.)



MxB

 

Wow- another angry and bitter person. You and mrvette been huffing TEL?

Has anybody ever seen a cylinder head from a Corvette with eroded valve seats? No, didn't think so. Neither have I.

 

Back to fuel additives then - modern high density fuels (that's another thing that's changed over the past thirty years, the specific gravity or density of higher octane gasoline has increased) don't atomise effectively in carburettors. Carburettors of old were designed for fuels of old that flowed more easily. We continue to use the carburettors but the fuel has changed.

A simple fix for the density issue is to add one millilitre of acetone for every litre of fuel in a tank. This is sufficient to reduce the specific gravity of high density fuel so it atomises more effectively while retaining the benefits derrived from modern fuel, and your engine gains more power and runs more smoothly.

Low lead Corvette engines were introduced in 1974 with unleaded in 1975. Your 79 shouldn't need any cylinder or valve lubricating additives to happily run on modern unleaded fuel. Just try the acetone.


As a general rule, the higher the octane the more efficiently your engine will run - within reason. I only buy high octane fuel for my 74 Vette, 98 RON in Australia and add the acetone. I believe it's best to choose a suitable fuel, have your car tuned to it and then only buy that fuel. The ingredients of fuel changes slightly every tank due to blending constraints at the refineries but that's about the best motorists can do.

PS be careful of some high density fuels - Shell Optimax for example contains 5% ethanol (in Australia at least). Check before you decide on a fuel worthy of your pride and joy.

 

You're "polling the audience" and not waiting for a response? You can't learn anything if you already know everything.

What do you mean by "eroded?" I don't think that I've ever heard that term applied to valve seats that were recessed as a result of unleaded fuel. I'm not quite so daffy as to suggest there isn't anybody who hasn't used the term, but how does one even go about "proving" anything about it? What if the one guy who it happened to died before he could tell the world...would that still mean that nobody has ever encountered it? Why dismiss the possibility simply because your experiences don't include it?

I know an awful lot of people who claimed to have "Corvette heads" on their small blocks in the 60s, 70s and 80s. There must have been an epidemic of headless Corvettes wandering the planet before commercially available factory and after market heads became readily available, better performing and cheaper than the cost of repairing old heads.

Now if we could just figure out how to get all of these environmental terrorists lined up in one place long enough to point at the sun and tell them the REAL reason behind "global warming."


MxB