What happened to gasoline in the mid 1970s?

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Norbert Schmidt

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Hi,

I wasn't around in the mid 1970s. I've been reading old threads here that containing "octane" and reading articles on the web. What I've gathered is the following which may be mostly wrong. I'd love to know what the real story is.

Before the mid 1970s, people used leaded gasoline that had approximately 88 octane. The lead acted as an anti knocking agent and compression ratios could be as high as 10.5 like in a Chrysler 340 engine. High compression meant a more efficient (chemical to mechanical energy conversion) and higher performing engines. Cars were fun and sounded good.

Sometime in the early 70s the US government required catalytic converters on cars to reduce carbon monoxide and unburned hydrocarbons emissions. The catalytic converters restricted flow, reduced horsepower, and made the cars sound pathetic. Leaded gas was cogging up the catalytic converters so cars with catalytic converters used unleaded. Unleaded gasoline would knock in higher compression engines so compression was lowered to something like 8 or 9 and the cars were no fun anymore. How crappy was the unleaded gasoline back then? What was its octane? Did it have any anti-knocking agent in it at all?

I'm guessing that over time pump gasoline became higher in octane again. Now we have ethanol (which has its own issues like water absorption) in gas and ethanol is higher in octane. So we can have 91 pump gas and higher compression engines again like 10.5 and higher. I read that really high efficiency engines like Mazda Skyactiv has 14:1 compression ratio and still passes emissions requirement tests. Cars can be fun again and with high flow catalytic converters still not spew out masses of pollution and sound respectable.

How much of that is correct? What's missing?

Thanks!
 
Smog and ever increasing higher pollution standards.

I would look at what Larry Widmer is doing and start there.
 
You are in the ball park. THere was a long road of learning what worked, what didn't and how it all developed. The stories that I hear......
Air pollution controls started in the late 60s. PCV systems had no impact on performance but did help some. Air injection into the exhaust stream was common on GM cars starting in 1967 or 68. Ignition timing and leaner carburetor settings were implemented but the engines could be tweaked to run "right" by any gas station mechanic.
The Feds wanted even cleaner air and had several suggestions on how to get there but as with any Government program, they look years ahead to enact incremental changes.
Electronic ignition systems were developed and in place by most manufacturers by 1974. Catalytic converters were pretty much everywhere by 1975. A single pipe on 4 and 6 cylinder engines, dual pipes merged into Single exhaust on V8s.....through a restrictive converter. The converter had to be restrictive to slow the exhaust long enough to clean it up. A converter that flowed well didn't have enough impact on the emissions. The factories found that the exhaust had to be hotter to burn off more of the emissions so some cars were fitted with pumps that injected fresh air into the exhaust stream. This caused an chemical reaction, raising the exhaust temperatures.
Compression ratios were dropped to the high 7s to low 8s in the vain attempt to run without detonation on low octane 87 unleaded fuel. Don't be fooled though. Published compression ratios of the Muscle car era were bullshit. My own '70 383 was rated at 8.7 to 1 but calculated to 8.12. The ratings for the other engines are likely just as wrong.
Closed element air cleaners with the intake bypassed to a heat stove pipe attached to the exhaust manifold supposedly aided in faster warm up periods. All of these efforts worked fairly well when new but they didn't age well. Chrysler had their "Lean Burn" system that had a lot of tow truck companies rich!
What first looked like D O O M for the auto industry turned out to be the savior.....Onboard computers! The computer, along with EFI, made the cars run better, get better mileage, produce far fewer emissions and last a lot longer. Precise metering of the fuel and the constant ability to react to different conditions allowed the engines to make more power than ever. There is NO way that a Challenger Hellcat or Demon would have ever made 707 or 843 HP and pass emission testing without a computer.
 
The simple answer is the gobt/ EPA wanted lead out of gasoline. Lead containing chemicals in gas was THE octane 'thing' back in the day. tetra ethyl lead, also back in the day called "ethyl" meaning you wanted the high octane stuff instead of "regular."

And of course emissions controls in engines BEFORE decent EFI just 'finished things off" Engines were lower and lower compression, leaned way out, retarded timing, ran hotter, less power, "afterrun" also called "diesling" IT WAS AWFUL

Emissions controls were several and combined. Lean out the carb A LOT, retard the timing and slow down the advance curve, lower compression to use lower octane fuels, and in the case of most all GM and Ford use "smog pumps" which pumped air into the exhaust manifolds to "burn off" leftover chemicals. In later years, catalitic converters were added to the exhaust. Exhaust recirculation EGR to reduce part of emissions. And various stop gap controls on the engine

Some wiki on "ethyl"

Tetraethyllead - Wikipedia
 
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By the way if you are the least bit familiar with Jimmy Doolittle, he did LOTS of important work besides the famous "Doolittle Raid." he worked with Shell to improve aircraft fuels and performance, helped develop high altitude aircraft oxy breathing systems and instrumentation, and helped do research and testing in various aircraft navigational instruments.
 
I rember buying 104 octane leaded at unocal (union 76) post 1980.

What I don't get is if a high compression engine can produce more HP per gallon why did we go to lower octane gas?

It seems like higher compression and higher octane wound be more efficient and that trans lated to more mpg
 
I remember that the whole effort was to reduce the emission of oxides of nitrogen (NOx) which was the cause of photochemical smog in major cities. It was found that higher cylinder temperatures resulted in higher amounts of NOx and, by reducing the compression ratio of the cylinder, the reaction temperature was lowered enough to reduce the amount of NOx. The catalytic converters could then be more efficient in breaking up the NOx products. The lower compression ratios allowed for more “regular” gas to be used instead of the higher octane rating gas.
 
I don't see where variable octane was mentioned.

Most stations had different grades of fuel and you could select regular, super, or premium each with a higher octane rating than the last.

They all had different names for each. IIRC Sunoco was 220, 240, 260.

Some stations had different pups for each blend, some had dial selectors on the same pump.
 
I remember like MoparLeo, Union 76 had a crank on the side of the pump and you cranked it to a setting of between 90 to 109 to get the octane you wanted, I had a 69 Superbee and I ran 105 all the time.
 
Sunoco pumps were grades 190 to 260.
I think/remember 260 was the industry high at 112 octane.
Cost -
190 was 24.9 cents per gal
260 was 44.9 per gal
Fuel trucks dumped 190 and 260 and the pump did the 'blending'

A brand new loaded 340 A-Body = $3500.00
 
MoparLeo said:
104 octane leaded after 1980 ?? Local gas station ? What state, wasn't California
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Was California, Costa Mesa, and the Unocal on 17th street. I turned 18 in 1980 and was able to get my driver's licenses finally that's why I remember it.

Thinking back I can't say will 100% certainty it was leaded, but for a few years I could get it at that station. Then it was gone.

Found this (can't vouch for it's accuracy, but...)

"1996: EPA bans the use of leaded fuel for on-road vehicles (leaded gasoline was down to 0.6 percent of 1996 gasoline sales). Lead is still used in some aviation fuels"

So maybe it was leaded as I remember.

Looks like the station is still there, looks a bit more modern, that's my Jack in the Box next door, and Alpha Beta market was just down the street, where I had a check cashing card ( pre ATMs)

Screenshot_20210515-082256.png
 
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MoparLeo said:
104 octane leaded after 1980 ?? Local gas station ? What state, wasn't California.
Click to expand...
You could still get 88 octane leaded gas until the early 90s in parts of California. I lived in Carmichael and a new ARCO station had 88 leaded, 87 unleaded and 92 Super unleaded. Later they reduced the 92 to 91.
 
The lead in the fuel also acted as a lubricant. When I rebuilt several engines back in the late seventies, I had to change out the valve guides to accommodate the lead-free fuel.
 
The little mom and pop station where I worked up until high school had 100 no lead and 108 leaded on the side pumps until about 1984, when it was just no longer makin money. Up to that point, they were they go to for all the hot street cars around the area. Stations (at least around here) can still get "whatever" gas they want. There's a station down the road from us right on the Jones County line that sells 114 leaded VP race gas right out of the pump. He has as long as I can remember. That's where all the local mud boggin guys go.
 
Southern California: in the late 1970s I had a built 361 big block in my 64 Dodge Polara 500. As a last gasp effort to keep it using leaded gas I would mix the lower leaded octane with the unleaded higher octane. The alternative was to go buy aviation gasoline because it was still leaded.
 
The Air Pumps (Smog Pumps) had an additional effect on exhaust gas emissions. By adding air to the exhaust, tailpipe emissions were diluted giving cleaner readings.
 
i pumped gas in the mid 80s we still had leaded then i think that was 86. I don't remember the octane. I do remember Sunoco ultra 94 was the chit in unleaded.

I remember guys with older cars "mixing" the leaded ...half tank of that with a half of Ultra 94.

what i can tell you obviously is leaded gas got phased out. I still see some signs in farm country that they sell leaded, but i do not know if it is the same as the old days.
 
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Hi,

Thanks for all the responses!

Lead, carbon monoxide, unburned hydrocarbons, nitrogen oxides. All seem like good things to keep out of the air.

It looks what I read about 88 unleaded octane was wrong. There were multiple grades available back then too up into the 100 octane range. That makes the modern struggle to keep engines away from knock make more sense to me.

An interesting discussion of how octane rating changed from RON to MON. So comparing old and new octane numbers is like comparing gross and net engine horsepower.

What octane level was the standard for premium in 1970? - ClassicOldsmobile.com

Octane rating conversions - PencilGeek's BMW Blog

Sunoco still makes 100 (R+M)/2 octane fuel that is street legal inside and outside California. A quick search indicates it is very expensive.

260 GT is a street-legal, oxygenated, unleaded gasoline designed for high performance street cars, muscle cars, classics, street rods, motorcycles, and the like.
Click to expand...

Sunoco Race Fuels

Sunoco Race Fuels

A car needs race fuel when it requires a fuel with specific properties in order to reach its full potential. This could mean needing a higher octane to allow for power gains from tuning. This could also mean a stable fuel that won’t break down when stored in a classic car for years between use.
Click to expand...

Everything you ever wanted to know about Sunoco Race Fuel — but were afraid to ask

All gasoline brands have both pure and ethanol-containing gasoline under the same brand names. For example, Shell V-Power ranges from 91 to 93 octane both with and without added ethanol. It just varies from station to station, and it's up to the station owner whether or not to sell pure gas.
Click to expand...

about pure-gas.org

Realistically, it looks like the options available in my area (British Columbia) are Chevron Supreme Plus 94 and Shell V-Power NiTRO+ Premium 91. Petro-Canada 94 is only available in other provinces.

Chevron Supreme Plus, 94 octane is ETHANOL FREE and available at all Chevron locations in British Columbia.
Click to expand...

https://www.chevronwithtechron.ca/carCare.aspx

Chevron Supreme Plus 94 octane is currently 1.679 CAD/liter in my neighbourhood. That is only 3 cents more than Chevron Supreme 91 which has ethanol. (Journie rewards programs can save 3 to 10 cents per liter.)

The 94 comes out of its own dedicated hose and nozzle.

1.679 CAD/liter * 0.8259 USD/CAD * 3.785 liter/US gallon = 5.249 USD/US gallon. Not so bad. About 5 years ago, I remember paying around 5 USD/US gallon in California for regular!

Shell V-Power NiTRO+ Premium 91 also has no ethanol but it comes out of the same hose and nozzle as the lower grades with ethanol. Some lower octane fuel with ethanol from the previous person's fill would likely make it into the next person's premium fill. Currently 1.959 CAD/liter. Just 2 cents less than Chevron 94.
 
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IfItsGotWheels said:
The Air Pumps (Smog Pumps) had an additional effect on exhaust gas emissions. By adding air to the exhaust, tailpipe emissions were diluted giving cleaner readings.
Click to expand...

Yeah, well......and no. The reason air pumps were added is because converters must get to at least 600 degrees F to operate properly. They had to add the air pump to heat the exhaust up so the converter would work and remove the nasties it was designed to. The added air was not to dilute the exhaust, but to make the converter work. The end result was cleaner exhaust, though.
 
Call me crazy but I still have the smog pump on my Fox Body. Hard to find them stock like that .I am thinking about bypassing it though.
 
Norbert Schmidt said:
unburned hydrocarbons
Click to expand...

Another fallacy. There is no such thing as "unburned hydrocarbons". Hydrocarbons are a byproduct of BURNING fuel. Spent, burned fuel. Hydrocarbons cannot be emitted without fuel being burned. So the correct term would be "unburned fuel".

This is where my opinion differs greatly from that of the "exhaust police". I recently commented about this in another thread.

The way "fuel sniffers" have been programmed since the beginning is, they check for hydrocarbon emissions. If hydrocarbon emissions are more than "whatever" amount is allotted for a given car, or year, or "however" they regulate it, the vehicle fails.

I think this premise is incorrect. It's my belief the MORE hydrocarbons emitted, the more EFFICIENT an engine can be. Take hot rodders, for instance. Most hot rodders keep their mills tuned to the Nth degree. That means advanced timing, correct heat range plugs in good condition, perfect tuneup and so on.

I've always thought the sniffer should check for UNBURNED FUEL. In this way, it would be checking for total efficiency. To me, it makes more sense to use more of the available energy in the fuel. The way it is now, it set up so that the least amount of energy used from fuel nets you the "cleanest" results.

So which way is "more clean" ultimately? ........AND is it REALLY a big enough difference to give a damn about?
 
Dana67Dart said:
Was California, Costa Mesa, and the Unocal on 17th street. I turned 18 in 1980 and was able to get my driver's licenses finally that's why I remember it.

Thinking back I can't say will 100% certainty it was leaded, but for a few years I could get it at that station. Then it was gone.

Found this (can't vouch for it's accuracy, but...)

"1996: EPA bans the use of leaded fuel for on-road vehicles (leaded gasoline was down to 0.6 percent of 1996 gasoline sales). Lead is still used in some aviation fuels"

So maybe it was leaded as I remember.

Looks like the station is still there, looks a bit more modern, that's my Jack in the Box next door, and Alpha Beta market was just down the street, where I had a check cashing card ( pre ATMs)

View attachment 1715737715
Click to expand...
"It's a model made before catalytic converters so it runs great on regular gas" Elwood Blues
 
Hydrocarbons:
Fuels are made up of hydrocarbons and some small quantity inorganics.
When burned the Hydrogen and carbon are seperated and join with other components mostly oxygen, and turn into something else.
The something elses are generally CO, CO2, and various NOx combinations and some leftover (or possibly altered) HCs. Depending on the temperatures, mixing etc there is sometimes also H2O, and various Ox.

It is absolutely correct that higher HC is to be expected in the exhaust when the engine is at or near full load because it will be using relatively rich mixtures. It's also when there is the least amount of O2 leftover.
upload_2021-5-15_14-10-15.png


Back when I had pre-cat cars a chart like the one above was helpful in knowing which way to adjust idle mix if it didn't pass the idle sniff test.

From Motor Gasolines Technical Review
upload_2021-5-15_14-22-54.png


upload_2021-5-15_14-25-34.png

p. 31
PDF for download.
 
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