Octane Rating & Spark Plugs

[Guest dnoz]

I have a 1913 buick and use Mobil 87 octane unleaded gas. It was suggested that I use Amoco 93 octane (white gas). Is the octane rating too high and cause it to run too hot? <P>Second, the standard plug is an AC 76-S. Can't senm to find them. I was sold champion 20's and not sure if this is the right plug. Does anyone know a replacement or where I can get the 76s's<P>

[Guest]

The higher octane gas might allow you to run more spark advance but I don't think you'll notice any difference in operating temperature. Stick with plain old regular gas.<BR>My AC chart shows C77L for Buicks up through 1928.

[novaman]

my champion book says W18 for buicks thru '28. The W20 would be a slightly hotter plug. <BR>The AC78S crosses over to a W20. The AC76S would be a colder plug than the AC78S(my book doesn't show the 76S) therefore should equal the W18.<BR>Hope that helps.<p>[This message has been edited by novaman (edited 11-20-2000).]

[Guest]

Gas 1st, Plugs 2nd.<P>I have NEVER used anything other than 87 octane [or lower at higher altitude, 85 here at 6000 feet] in any car built before WW II.<BR>Look at the compression ratios in those years.<P>I own a 1914 Buick B-25 which I drive extensively on tours, and I don't mean local tours. I use AC C-77L plugs and they perform well. Better than available Champions.<P>To the best of my knowledge they are still being made and I have been getting them here in Cheyenne. Not cheap at about $40 something for a box of 8. The dealer tries to keep a box in stock for me, but others have found that out and so now he may not have them when I go in. It does take a while for him to get them from the factory.<BR>If you can't find them where you are I would be willing to get them here and ship them to you. This is NOT a business with me. I wouldn't go to that trouble if it were my business. Let me know if you need a box.<BR> Howard

[ply33]

Don't know a thing about spark plugs for that era. But I think I know a little about octane <P>"Too high" an octane gas will do nothing harmful in an engine. It will not run hotter or cooler. Nor will produce more or less power. It will, however, cost you more to fill the tank.<P>Too low an octane rating and you have problems: Knock, pre-detonation, ping. What ever you want to call it, its bad. It causes loss of power and localized heating and extreme pressure. It can lead to burned valves, burnt pistons, ruined bearings, etc.<P>What determines how much octane your car needs? Mostly compression ratio.<P>As hvs noted, no pre-WWII car has a high enough compression ratio to require a high octane rated fuel. The typical octane values for fuel in the 1930s was in the 60s to low 70s. Your 87 octane (or in the mountain states 85 octane) gas is way in excess of what you need.<P>Do however, check those rubber parts in your carb and else where: Modern gas will distroy some of the old materials.

[Guest]

EVEN THE POOREST GAS NOWADAYS, IS FAR SUPERIOR THE THE GAS OF THE TEENS. MOST ENGINES OF THAT ERA HAD A COMPRESSION RATIO OF 3-4 TO ONE WHICH DOSENT REQUIRE MUCH IN THE WAY OF OCTANE.

[ThomasBorchers]

I agree with Tod. At the time as the Buick was built they had only a very low octane rate. I think at this time they dreamed for our todays gas.<P>Tom

[Guest]

I agree with TodFitch but would like to add one thing. Regular grade fuel actually has a higher "Driveability Index" (DI) than premium fuel. I can't explain it all (see an SAE handbook or equivalent if you must know) but it has to do with how well the car starts and drives. This is a rating that the fuel companies and auto companies use, and while it is measurable, it's not something that you'll see posted at the pump!<P>I work at one of the big three auto companies and can tell you that even "premium only" cars leave our plants with "regular" grade fuel in the tank. This is more because of better startability, reduced plug fouling (during yard marshalling), etc. rather than the cost difference between the two grades.<P>For this reason, regular fuel is actually superior in most cars--assuming the higher octane is NOT needed to prevent knock. <P>I'd also suggest that for an older car, all fuels (regular OR premium) with ANY alcohol content (ethanol) by avoided. It's a cheap way for the refiner to boost octane, but is harmful to many fuel system components in cars made before about 1990.<P>Greg Cockerill<BR>BCA #36864<P>

[Guest]

Has anyone successfully bought non alcohol added gasoline in Nebraska or Iowa recently.<BR>Good luck. I'm not sure it's available here in Wyoming either. Worse yet, it seems that it is no longer a requirement that the pumps be marked "contains alcohol", at least in those states. <P>On the Glidden Tour this year in Tucson, there was NO non alcohol added gas to be found. The pumps there were well marked.<BR>We had to use it and pray everything holds together. Damn <P> hvs