What gas should I use??? 1939 LaSalle

[POB]

I recently bought a 1939 LaSalle. I purchased it from the daughter of the previous owner who had passed away.  I was told by her and the "not so friendly mechanic" that did work over the years on the vehicle that 87 octane would be fine, but was given no explanation why (knowing some older vehicles requie a lead based fuel) I know the coupe was restored in the late 80's but don't know for sue what fuel the previous owner used......... I know I can purchase a lead fuel additive or is strait gasoline fine like the mechanic said?

Thank you in advance........please give me your input, I don't want to trash the motor!!!!

[Carl Fielding]

Daughter and crusty old mechanic gave you good advice. 87 is more than enough for your car. As a general rule of thumb for octane requirement : 10x the compression ratio. So for a 6.5 compression ratio (is that what your car is?) , the 65 or 70 octane gasoline of its day was perfect. The biggest favor you can do for your engine is to use a high quality multi-viscosity full synthetic oil in it. Like 10W/30 if you live in a moderately cool area , or 15W/40 in warm regions. Mobil 1 , Amsoil , are  true synthetics , as are others. Castrol ? Uh uh. Amsoil has a fairly new line which has ample zinc and phosphorus for old flat tappet engines. I want to check into the new Penzoil synthetic made from natural gas. Make sure the cooling system is in great shape. If the radiator is at all questionable , rebuild it. Please tell us more about your '39. You know how much everyone loves pictures. As a teen age kid , I learned to drive a standard transmission on a large-bore '39 LaSalle. A 4 door Cadillac 61. I liked it so much that I went out and bought a dark blue '39 Cad 60 S for $100.   - Carl

[35-709]

I would add that if the car is going to sit a lot, use an additive like Sta-Bil in the fuel according to directions on the bottle.  I do not use or recommend ANY "snake oil" fuel additive but Sta-Bil works and is necessary in my opinion to help keep the ethanol laced fuel we have to deal with today from going bad --- which it will.  Non-ethanol gas (boat gas) is available at some gas stations (or marinas) which would be even better but it is harder to find, more expensive and higher octane (usually about 90) which won't hurt anything.
   
Sta-Bil is available at many places including WalMart, any auto parts store, hardware stores, Home Depot, Lowes and so on.

Am in full agreement with Carl Fielding's recommendations on motor oils.

[cadillac ken]

The oil you use is far more important than the gasoline choice.
Not using an oil with the added ZZDP will be a mistake.  Brad Penn or Joe Gibbs is what I use.  As pointed out the new oils will kill a flat tappet motor as they do not have the necessary ZZDP to prevent excessive wear.

Ken in FL

[35-709]

Agreed, and as Carl pointed out --- "Amsoil has a fairly new line which has ample zinc and phosphorus for old flat tappet engines. I want to check into the new Penzoil synthetic made from natural gas." 
Mobil 1 does too in some of their oils as the list I posted a link to here a while back shows, 15W-50 being one of them.  Care should be taken to assure enough ZDDP is present in whatever oil is used in flat tappet engines.

[POB]

Thanks for the advice.  I did order a Lead Additive through Amazon which I figured could not hurt, right or should I return it?.... Zink oil is a must, thanks for drilling it in my head guys!!!! And yes it's the standered 322-cu.in, 125hp monobloc V-8 engine or the Series 50 that came with the vehicle.

[35-709]

Very nice looking LaSalle.
"Lead" additive won't hurt, not needed though.