A question about Gasoline Grades

[tigersdad]

I recently purchased another car, a 1957 Ford Fairlane 500 Convertible (Sunliner) with the 312/245 V-8 Thunderbird engine. The car has been completely restored. My question is: What would be the best grade of gasoline to use in this car? In the original Sales Manual it calls out for Supreme for the highest performance for your engine, but that was leaded gas in those days. What about today? I usually add a lead additive to my older cars every once in awhile.

Thanks!

Jay

1931 Cadillac 355A Town Sedan

1934 Buick Model 40

1957 Ford Sunliner

[john2dameron]

That engine had a 9.7:1 compression ratio. The best gas you can find today probably will not match up to what that engine liked to run on when it was new. Therefore to my way of thinking, whatever you put into it today is at best a compromise.

[jscheib]

My suggestion - as high an octane rating that you can get, without ethanol. I have heard it might be helpful to mix in some racing fuel (rather then octane booster chemicals) also with high compression engines, but you are not supposed to use that for road vehicles, I believe.

John

[Rusty_OToole]

As a general rule, your octane should look like your compression ratio. For 9.7:1 compression you would want 97 octane.

This is not an exact rule just a general guide. I would try 92 octane hi test and add an octane booster if necessary or dial back the spark advance.

Since your engine was made for leaded gas an additive to protect the valves from burning would be a good idea, if it has not had the valves and valve seats replaced.

If the engine was completely restored it probably had them replaced. The rebuilder or previous owner should know. No need to worry about valve wear if you have hardened valve seat inserts and new exhaust valves.

Edited September 17, 2010 by Rusty_OToole (see edit history)

[ply33]

As a general rule, your octane should look like your compression ratio. For 9.7:1 compression you would want 97 octane.

This is not an exact rule just a general guide. I would try 92 octane hi test and add an octane booster if necessary or dial back the spark advance.....

You might want to look at 7. What parameters determine octane requirement? Go down a little to a table that gives compression ratios versus octane requirements.

Looks like you will want something between 96 and 100 octane. And, at least where I live, that is not available at the local filling stations.

[tigersdad]

Everyone,

Thanks for all your help. Out here in CA, where we still pay $3.50/gallon for premium, seems like premium would be the best bet (though I think the octane is only 91). It's 87, 89 and 91 out here. Rusty, thanks for the information on the valves. I'll check with the Jerry Hill to see if that was done.

Jay

[Rusty_OToole]

That is a very good explanation of the role octane ratings play and what they mean. A couple of things are worth emphasising. One is, octane tells you the knock resistance of the fuel and nothing else. Another is, you need the correct octane for best performance, either too high or too low is not good.

One thing I take issue with is the relationship of octane to compression ratio. Their chart is good in the higher ranges but does not apply to our old cars in the lower ranges. Prewar cars with 5:1 and 6:1 compression did not require octane anywhere near as high as they say. Such high octane fuel was simply not available at that time from normal gas stations.

[Guest Moepar]

After speaking with an American Petroleum Institute engineer, I found out that the higher the octane, the more ethanol is added to achieve that. At stations that sell gas with ethanol, 87 octane has 10%, 89 & 93 more than that to get to the higher octanes.

If you can find a station that does not have ethanol in the gas, I'd try to use that in your Ford.

[Guest Kingoftheroad]

My classic runs a bigger engine with more compression (Stock) and it runs good on 89 or 91 octane. Not so good on 87 octane... I also run lead additive to protect my valves..

[Guest mercman86]

I run preimum in my Ranchero, It dosent like reg 87 at all. I also run a "lead substitute" that I get from my local parts place. On the bottle, it says that it will also increase octane as well as add the lead protection. Somthing to look at when purchasing a lead additive.

[Reatta Man]

Can you still get lead substitue in "everything is restricted here" California?

[tigersdad]

Thanks, guys! Very informative on the Octanes and lead substitutes.

Jay

[huptoy]

Last week, I filled my 3.8 2008 Buick Lucienne in Ohio with 89 Octane (10% ethanol) and drove 450 miles at 70 MPH getting 27.3 MPG. On the return, I filled up in Iowa with 87 Octane (zero ethanol) driving 450 miles at 70 MPH and got 31.4 MPG. In Iowa the ethanol gas was $2.55 a gallon. With all gas, the price was $2.69. The total cost with ethanol was $42.03 versus $38.55. This was a savings of $3.48. From my experience, I will always skip the ethanol gas additive when given the option.

[Reatta Man]

Last week, I filled my 3.8 2008 Buick Lucienne in Ohio with 89 Octane (10% ethanol) and drove 450 miles at 70 MPH getting 27.3 MPG. On the return, I filled up in Iowa with 87 Octane (zero ethanol) driving 450 miles at 70 MPH and got 31.4 MPG. In Iowa the ethanol gas was $2.55 a gallon. With all gas, the price was $2.69. The total cost with ethanol was $42.03 versus $38.55. This was a savings of $3.48. From my experience, I will always skip the ethanol gas additive when given the option.

I wish we all had the choice of paying a few more pennies to get real gas. Here in Texas, ethanol is in EVERYTHING. And, when ethanol was forced on all the stations, the price did NOT go down.