What was leaded - unleaded transition like? Octane?

[repairman54]

When cats were implemented on US vehicles the restrictor in the filler neck was introduced. Smaller diameter unleaded nozzle would only fit into the filler neck as leaded nozzles were a larger diameter. That was so cheaper leaded gas would not be easy to put into an unleaded vehicle killing the cats.
Yeah I'm that old.
I had a '79 318 Dodge van that I pulled the cat off, removed the filler restrictor and ran leaded in it for a long time. 10 or 15 cents a gallon cheaper was a big deal back then. I had to put it back together when NJ started inspecting trucks under 10k registration weights. Was a 8k registration prior with self inspection non commercial so I could run the Garden State parkway. Put 200k miles on it and sold it running fine. Never touched anything on the motor in that time. Just ballast resistors and ignition boxes.

 

[DBMaster]

The phasing out of leaded gas was happening during my college years, the late 1980s. I had a 1972 Pontiac Catalina at the time. Engines that were 1971 and newer had hardened valve seats. The 400 ci V8 in the car had only 8.2:1 compression, but still knocked like a box of marbles with regular unleaded. After updating the distributor (from points to HEI) I was able to adjust the advance curve with a weight and spring kit. I got it to the point at which I could "get away" with using mid-grade gas.

 

[Astro_Guy]

See

 

[Snagglefoot]

The phasing out of leaded gas was happening during my college years, the late 1980s. I had a 1972 Pontiac Catalina at the time. Engines that were 1971 and newer had hardened valve seats. The 400 ci V8 in the car had only 8.2:1 compression, but still knocked like a box of marbles with regular unleaded. After updating the distributor (from points to HEI) I was able to adjust the advance curve with a weight and spring kit. I got it to the point at which I could "get away" with using mid-grade gas.

We had a 76 Catalina with a 350. That series was like a floating boat. It was our first exposure to unleaded fuel.

 

[Snagglefoot]

The roll-out of unleaded fuel was pretty quick up in western Canada and I recall regular fuel was available for a long time. At the time we owned a 74 Datsun that took regular fuel and the 76 Pontiac Catalina that took unleaded. There was a lot of hand wringing about the lack of lead and it’s effect on valve seats. Leaded fuel was finally banned in Canada in 1990. It’s funny we still call it unleaded fuel 35 years later. I think I’ll have another un-creamed coffee.

 

[Opelman]

Octane was calculated differently, premium leaded was 100 octane, regular was 93 octane I think and super premium was 104. Sunoco used to have a pump to select up to 104. The transfer to mtbe as a substitute for lead was gradual and octane ratings started to be calculated differently.

MTBE was an oxygenate, not a lead substitute. MTBE turned out to be really nasty stuff, so now ethanol is used instead.

 

[y_p_w]

MTBE was an oxygenate, not a lead substitute. MTBE turned out to be really nasty stuff, so now ethanol is used instead.

It kind of was in a way. The primary reason for TEL was its antiknock properties. And it was impressive. I’ve read up to 20 AKI points.

MTBE was somewhat different. That has a blending AKI octane rating of maybe 110 to 119. That’s about the same as ethanol, but the standard was up to 15%. I believe for typical gasoline MTBE might have boosted it about 3 AKI points.

 

[y_p_w]

MTBE turned out to be really nasty stuff, so now ethanol is used instead.

In terms of toxicity, MTBE is considered less toxic than base gasoline. The biggest issue was that tiny amounts contaminating water would be noticeable in terms of the taste. But other than that, it’s not really all that nasty.

https://www.aahealth.org/environmental-health/wells-septic-systems/mtbe-well-water​

A drinking water standard has not been established for MTBE. In 1997, the U.S. Environmental Protection Agency (EPA) issued a drinking water advisory indicating taste and odor problems may be experienced at levels of 20 to 40 ppb. A value above the drinking water advisory does not indicate that harmful effects will occur, but that taste and odor problems may be experienced and a risk exists that should be evaluated.​

Now lead is clearly nasty.

 

[Opelman]

I remember the fuss in CA when MTBE started showing up in the water supply. That is when we got switched to ethanol. When MTBE was added to our fuel, the car I was driving at the time lost 3 mpg. That was a 15% drop in fuel economy. Drive out of state and fuel up, mpg picked right up. Please no funky performance killing additives in my fuel. Ethanol belongs in my drink glass, not my fuel tank.