1970 LS-5, gas at the pump in 1970

[Donald A.]

Not being of age to know what was at the gas pump in 1970 I've wondered what fuel was most likely chosen for my 70 LS-5.

Understanding that in the late 60's there were still cars with high CR's was the 70 454 at 10.25 still considered high compression at that time?

What I'm asking is this, do you think that folks who bought these cars new were putting in high octane fuel of the day, like 100 octane? Or was this car considered a "regular" pump gas car?

what was available at the pump then and what is equivalent today?

Just wondering what would happen if I put in some Aviation gas. Best I can get in my area is 93 at a standard station

thanks

[Don H.]

Re: 1970 LS-5, gas at the pump in 1970

Hi Don,

Back in 1970, a gallon of hi test or white pump gas cost about 33 cents a gallon. Then it jumped to about 42 cents per in June 73 in the oil embargo/gas crisis.
So, hi test only cost a few pennies more a gallon that regular. Note in the info below that the 93 octane you buy today where you live is not far below the actual octane rating of the hi test back in 1970. It is just missing the lead, today, and features that darned corn extract. Most guys with performance cars like yours were probably feeding it hi test.

Here is something I pulled from Chevytalk.com. I think it is pretty accurate.
"The 93 octane of today is actually not that much less octane than the octane of the Premium pump gas of the 60's and early 70's. Here is why:
100 advertised octane was common and Hess even had 101 octane for a few years. Sunoco260 gasoline was 102 octane. Those octane ratings sound very high compared to today's octane ratings, but they were not as much higher as you would think. That's because the advertised octane back then was based on a different measurement than we use today. The reason is that there are 2 ways to rate octane. One is called the "research" octane number and the other is called the "motor" octane number.
The research octane number is a higher number than the motor octane number, so when oil companies used to advertise their Hi-Test gasoline, they used the more impressive research octane number, in this case, around 100 octane.
But "motor" octane is a number about 10 points lower than the Research number. The oil companies didn't advertise that lower number.
In the early 70's, the government decided to require oil companies to post an average of the 2 different octane ratings, which lowers the octane rating number for the same fuel that had higher numbers before. So, ever since then, when you look on a gas pump, you'll see a sticker for the octane rating that says "R+M/2", which stands for Research octane plus Motor octane divided by 2, which is the average of both rating numbers.
Therefore, the old Premium from the 60's, that was 100 Research octane, also had a Motor octane rating of about 90. So that same old 100 octane Premium would today now be posted as an average of 100 Research octane and 90 Motor octane, and would be 95 octane. That's still a little higher than the 93 octane of today's Premium, but not as big a difference as most people think. "

[Donald A.]

Re: 1970 LS-5, gas at the pump in 1970

Fantastic response. Thank you.

One of our local stations still carries 100 octane although I have not been there. Wonder if that is 100 octane using the current calculated method? Now I will have to go by there and look.

I found a site site online that lists every gas station in the US and exactly what fuel they carry. I will post that link. That is how I will know where the stations that carry 93 are at.

BTW, I'm very proud to say that in Oklahoma the stations have large signage advertising the fact that their gas is 100% real with no ethanol etc.

[Michael W.]

Re: 1970 LS-5, gas at the pump in 1970

Donald-

Your owners manual should state what octane level your car requires. I would expect to see somewhere in the area of 97-98 RON, but no higher. If it simply says 'premium or super', again that would translate to 98ish RON.

Most fuels today have a delta of 8 between the RON and MON number giving an AKI or PON of 94. Most owners can run these cars without issue on today's pump 93. If you're not experiencing detonation there's no need to run higher octane.

Without getting into the E10 dabate, 93 octane is 93 octane.

[Joe L.]

Re: 1970 LS-5, gas at the pump in 1970

Hi Don,

Back in 1970, a gallon of hi test or white pump gas cost about 33 cents a gallon. Then it jumped to about 42 cents per in June 73 in the oil embargo/gas crisis.
So, hi test only cost a few pennies more a gallon that regular. Note in the info below that the 93 octane you buy today where you live is not far below the actual octane rating of the hi test back in 1970. It is just missing the lead, today, and features that darned corn extract. Most guys with performance cars like yours were probably feeding it hi test.

Here is something I pulled from Chevytalk.com. I think it is pretty accurate.
"The 93 octane of today is actually not that much less octane than the octane of the Premium pump gas of the 60's and early 70's. Here is why:
100 advertised octane was common and Hess even had 101 octane for a few years. Sunoco260 gasoline was 102 octane. Those octane ratings sound very high compared to today's octane ratings, but they were not as much higher as you would think. That's because the advertised octane back then was based on a different measurement than we use today. The reason is that there are 2 ways to rate octane. One is called the "research" octane number and the other is called the "motor" octane number.
The research octane number is a higher number than the motor octane number, so when oil companies used to advertise their Hi-Test gasoline, they used the more impressive research octane number, in this case, around 100 octane.
But "motor" octane is a number about 10 points lower than the Research number. The oil companies didn't advertise that lower number.
In the early 70's, the government decided to require oil companies to post an average of the 2 different octane ratings, which lowers the octane rating number for the same fuel that had higher numbers before. So, ever since then, when you look on a gas pump, you'll see a sticker for the octane rating that says "R+M/2", which stands for Research octane plus Motor octane divided by 2, which is the average of both rating numbers.
Therefore, the old Premium from the 60's, that was 100 Research octane, also had a Motor octane rating of about 90. So that same old 100 octane Premium would today now be posted as an average of 100 Research octane and 90 Motor octane, and would be 95 octane. That's still a little higher than the 93 octane of today's Premium, but not as big a difference as most people think. "

Don------


The quote is mostly correct----only one small point of incorrectness: they state that there are 2 ways to rate the octane of gasoline, which implies there are ONLY two ways. There are actually more than 2 ways. However, for automotive gasoline there are only two commonly used----research and motor.

[Jim T.]

Re: 1970 LS-5, gas at the pump in 1970

Donald my 1968 327/350 11:00 and my 1970 350/300 10:25 did just fine on pump premium in 1970,they still do fine today on pump premium. The LS7 454 engine listed in my 1970's owner manual with 12:25 was not produced in 1970 Corvettes, wonder how it would of performed on pump premium?

[Joe L.]

Re: 1970 LS-5, gas at the pump in 1970

Donald my 1968 327/350 11:00 and my 1970 350/300 10:25 did just fine on pump premium in 1970,they still do fine today on pump premium. The LS7 454 engine listed in my 1970's owner manual with 12:25 was not produced in 1970 Corvettes, wonder how it would of performed on pump premium?

Jim------


Not very well. It required a minimum of 103 research octane and 95 motor octane. That would mean 99 octane by today's R+M/2 rating.

[Jim T.]

Re: 1970 LS-5, gas at the pump in 1970

Joe, I don't know what the 1971 Corvette LS6 had in the compression rating, did the LS6 do okay on pump premium?

[Jim D.]

Re: 1970 LS-5, gas at the pump in 1970

Joe, I don't know what the 1971 Corvette LS6 had in the compression rating, did the LS6 do okay on pump premium?

My 1970 LS6 Chevelle had an advertised CR of 11.25:1 and ran perfectly on premium pump gas up until the late 70's when I sold it.

[Duke W.]

Re: 1970 LS-5, gas at the pump in 1970

You will find a comprehensive explanation of "octane number" here:

http://stlouisncrs.org/news_files/DukeWilliamsEngineTuningPerformance&EconomySeminar.pdf

"Premium" gasoline from the sixties typically had RON ratings of 96-99. Actual octane numbers did not have to be posted and varied with region and season. Oil companies only blended sufficient octane to minimize customer complaints since higher octane increases cost.

"100 octane" was somewhat of a myth as most "premium fuel" engines would operate without detonation on somewhat lower octane, particularly in cold winter weather and high altitude.

Also, manufacturers equipped engines with conservative spark advance maps to keep the engines out of detonation in worst case conditions, which cost torque (especially at the low end), power, and fuel economy.

Some oil companies did market "super premiums" such as Chevron Custom Supreme (white pump) on the West Coast, and Sunoco offered many different octanes by blending at the pump. Chevron Custom Supreme and Sunoco 260 were in the range of 100-103 RON, but, again, they could get away with lower octane in winter than summer, so actual octane was not necessarily constant throughout the year.

Most OE Corvette engines will operate without significant detonation on modern pump premium, which may be as low as 91 PON. As built, most OE engines have actual compression ratios a half point lower than advertised, and most engines have been rebuilt with lower compression due to use of thick head gaskets and sometimes lower compression pistons than OE. None of this is usually necessary and just reduces broad range engine performance and increases fuel consumption.

Most engines that have been rebuilt with "low compression" pistons and thick head gaskets, which yields true compression ratios of only 8 - 9:1, will operate detonation-free on 87 PON regular unleaded.

Finally most engines regardless of actual OE or actual current compression ratio - and most owners only have, at best, a vague idea of what it might actually be - will respond very positively to optimizing the spark advance map, which will increase torque, especially at the low end, top end power, and fuel economy.

Duke

[Joe L.]

Re: 1970 LS-5, gas at the pump in 1970

Joe, I don't know what the 1971 Corvette LS6 had in the compression rating, did the LS6 do okay on pump premium?

Jim------


1971 Corvette LS-6 had a 9.0:1 compression ratio. That would run just fine on pump premium. In fact, my guess would be that it would do OK on 87 octane regular.

[Duke W.]

Re: 1970 LS-5, gas at the pump in 1970

As were all other 1971 GM engines the LS6 was designed to operate on 91 RON unleaded fuel, which is approximately equivalent in detonation resistance to today's 87 PON.

The LS7 was effectively a stoked L-88 with cast iron heads, which means it was not designed for road use. It was likely cancelled both due to low expected production volume and the cost of gaining emission certification if it was to be offered as a plant installed RPO.

Duke

[Donald A.]

Re: 1970 LS-5, gas at the pump in 1970

Thanks for all the great responses.

I found a station in OKC that had 93 so I tried a full tank. When I talked to them they said it actually was 94. Anyway I think my LS-5 really likes it. Car seems to be a little crisper on throttle response.

It is not a huge different but it was good to have the option. At $4.99 a gallon not sure I will use all thE time.

[Don H.]

Re: 1970 LS-5, gas at the pump in 1970

It might be a placebo effect Don, but what the heck. That's a great looking line up of heavy sharks.