News:

Due to a technical issue, some recently uploaded pictures have been lost. We are investigating why this happened but the issue has been resolved so that future uploads should be safe.  You can also Modify your post (MORE...) and re-upload the pictures in your post.

Main Menu

Which gas, octane vs ethanol? 331

Started by bullet bob, June 20, 2017, 07:46:25 AM

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.

bullet bob

I can't find any 93 octane fuel around here that is non-ethanol. My choices are either 93 w/ethanol or 90 "pure". I'm leaning towards the 90 pure but would like your input. Fuel pump has been professionally rebuilt. Thanks all. Bob
Honda Goldwing 1800  "I don't need no stinkin' map, I've still got gas"

cadman56

I started using EO87 in my 91 Brougham and was thrilled at how much smoother the engine ran and power was increased also.  The wife has to do the driving and she even remarked at the difference.  See what others may say but I would give the pure gas a try.  Larry
1956 Cadillac Coupe deVille (sold)
1956 Cadillac Convertible (sold)
1956 Cadillac Eldorado Seville (sold)
1967 Cadillac Eldorado (sold)
1968 Cadillac Convertible (Sold)
1991 Cadillac Fleetwood Brougham dElegance
Larry Blanchard CLC #5820

Caddy Wizard

The 331 runs well on regular and doesn't need high-test fuel.  In fact, it won't help the engine run better at all.  Non-ethanol fuel (regular grade) is best for the 331, IMO...

Art G
Art Gardner


1955 S60 Fleetwood sedan (now under resto -- has been in paint shop since June 2022!)
1955 S62 Coupe (future show car? 2/3 done)
1958 Eldo Seville (2/3 done)

bullet bob

Appreciate that Art. The memory's not what it used to be, but I thought the 331's required 93. I suffer from CRS!
Honda Goldwing 1800  "I don't need no stinkin' map, I've still got gas"

Caddy Wizard

No worries!  The 331 engine started out at something like 7.5:1 compression and increased over the years (starting with 52, i think).  They increased the compression ratio, while keeping the displacement the same, by decreasing the volume of the combustion chambers in the heads.  With the introduction of the 365 in 1956, the engine went to about 10:1 compression (maybe 10.5) and then needed hi-test fuel for sure.  The last 331, the 1955, had a compression ratio of about 9:1 and should be okay on regular fuel. Certainly, the early, lower-compression 331s from 1949-51 don't need hi-test.
Art Gardner


1955 S60 Fleetwood sedan (now under resto -- has been in paint shop since June 2022!)
1955 S62 Coupe (future show car? 2/3 done)
1958 Eldo Seville (2/3 done)

T J Lankes

You may already have this site for locating non-ethanol stations but here it is just in case you need it:

https://www.pure-gas.org/

D.Yaros

Regular worked just fine for me in my 1955 331 c.i. engine.
Dave Yaros
CLC #25195
55 Coupe de Ville
92 Allante
62 Olds  

You will find me on the web @:
http://GDYNets.atwebpages.com  -Dave's Den
http://graylady.atwebpages.com -'55 CDV site
http://www.freewebs.com/jeandaveyaros  -Saved 62 (Oldsmobile) Web Site
The home of Car Collector Chronicles.  A  monthly GDYNets newsletter focusing on classic car collecting.
http://www.scribd.com/D_Yaros/

bullet bob

Quote from: T J Lankes on June 20, 2017, 01:59:19 PM
You may already have this site for locating non-ethanol stations but here it is just in case you need it:

https://www.pure-gas.org/
Thanks. I do have that. The only thing around here is at the lake. 90 octane. $3.79/gal.
Honda Goldwing 1800  "I don't need no stinkin' map, I've still got gas"

Jay Friedman

90 octane is fine.  My '49 with a 331 runs perfectly on 87 octane non-ethanol fuel.
1949 Cadillac 6107 Club Coupe
1932 Ford V8 Phaeton (restored, not a rod).  Sold
Decatur, Georgia
CLC # 3210, since 1984
"If it won't work, get a bigger hammer."