39 LaSalle gas

[39lasalle]

We got the car running and I have just been putting in either 87 or 93 octane depending if I was filling up my Chevy II or lawn equipment. Now that I am going to start driving the LaSalle should I be using one or the other or just see how it acts on the cheaper stuff and then adjust accordingly?

I also have some of the lead substitute, should I be adding any of this as well?

Thanks

39

[Bobby B]

Car will run fine on regular, it's a low compression engine. I personally always use Premium because the car will sit for weeks or months on end, and it's cheap insurance along with some Sta-Bil. Might be heresay, but I think Premium does't break down as quickly as regular over the same time period. If you have Ethanol-free in your area, that would be my first choice. Unfortunately in NJ, it's not available unless I drive 2+ hours away to get it in PA. 
                                                                                                                                                                        Bobby

[Carl Fielding]

Well , if you are looking to go for a Saturday drive , fill 'er up with with 87. Immediate pre WW2 gasoline would not have been much over 70 octane , if even that. I'll leave additive and ethanol tips to others . Burning up a tank of straight pump gas will not hurt anything while you wait for direct annecdotal experience with gasoline and additives in these monoblock flathead V8s. Have you been burning moonshine (ethanol polluted) gasoline so far ?  - Carl

[39lasalle]

HA, moonshine..that is fer Drinkin'!!!    I have been using whatever was laying around never reallly ran for more than 10 minutes and rarely under load

thanks

39

[Carl Fielding]

High octane gasoline will result in higher EGT. You will get a less complete burn with it , and your exhaust valves may suffer. As I say , your engine was designed to run optimally on gasoline available in 1939. I received my flight engineers training 50 years ago. P&W R2800s (and a few other radials- DC-3s may still be making someone money somewhere , and I know LACSA flew C-46s well into the '70s) , were still in commercial service back then. So I was fortunate to have had both recip and turbine training. We were taught that using too high octane avgas could burn exhaust valves. Octane rating in your world refers to combustion flamefront propagation rate. The higher the octane , the slower the the flamefront propagation rate. Higher than spec octane will result in combustion continuing too long in the power stroke and into the exhaust cycle. Too high EGT and loss of power will be the result. We were taught that if only avgas of too high octane was available at whatever airport we needed fuel, take on only what was necessary for flight to next destination. Back here on the ground , your low compression engines will run cooler exhaust valves , get better mileage and develop more power on the lowest octane gasoline you can find. You will also benefit from setting your ignition timing just a little advanced over spec when using too high octane (87+ in a 7.00 : 1 CR engine). Maybe only 4 degrees or so on 87. If you are running at altitude , you may advance a bit more , as it is compression PRESSURE which actually dictates octane requirement. Oh , and a general rule for octane is 10 X the compression ratio. For example , 8.00 : 1 , 80 octane. Oh do I wish I could get 45 octane gasoline for my mid '20s Cadillacs. That is what gasoline was back then ! Perfect for my 4.5 and 4.7 compression ratio engines. You will enjoy that '39. I learned to drive a manual transmission on a little '39 model 61. My first drivable car when I was 16 was a '39 60S I bought for $100. Fast enough for modern traffic , large brakes , and handle fairly well.         
                              And leave the moonshine for the gas tank.  - CC

[Quentin Hall]

Thankyou Carl for your wonderful history lesson. Your knowledge and experience is what I love about this hobby.
Hard to believe there was a time when a 39 was a hundred dollar car. I'd listen all day to old stories like that. Wish i could instill that same interest in my 16yo son who shows absolutely no interest in the past. . .  Only the future. I guess that is why there was time when a 39 could be had for $100 though.
Guess the more things change, the more things stay the same.