Recommended Fuel

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jar84203

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Can anyone give their opinion on what type of fuel to use in vintage automobiles? Not for race purposes, just stock vehicles. Octane rating, additives, ethanol in modern gas, absence of lead, etc. Thanks
 
jar84203 said:
Doesn't lead increase compression ratio? I could be wrong
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No.

You only need a high enough octane rating to prevent detonation. So if you don't get detonation with regular unleaded, run regular unleaded.

Like was mentioned in post #2. A lead additive will help prevent valve seat erosion on older (pre 72 please correct me if my date is wrong) heads that have not had hardened seats installed.
 
jar84203 said:
Can anyone give their opinion on what type of fuel to use in vintage automobiles? Not for race purposes, just stock vehicles. Octane rating, additives, ethanol in modern gas, absence of lead, etc. Thanks
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Like others I would recommend verifying the compression ratio and use the fuel octane rating based on that, with a little margin. Mopars after 71 usually had very sad (low) compression ratios such as 8.0 to 1, so you can easily run 89 octane. Mix your fuel with a lead additive or similar valve lubricant additive, to prevent valve wear type issues, unless you are sure your engine has modern valves and hardened seats (and guides?). Also modern oils do not contain the proper additives to lubricate flat tappet lifters inside almost all old vehicles, which means it is very important to use an oil additive at every oil change that complies with ancient engine metal to metal / cam to flat lifter designs. Here is what we use: "Hughes Extreme Pressure Oil Additive - (1 Pint)". Mancini Racing sells it.. A flat cam is a depressing state of affairs.. My two cents..:)
 
calebsmopars said:
i run half a tank of e85 and half tank of 91 octane its a perfect combo!
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I don't know what to tell you other than you must have been running pig rich to start with. Pure E-85 runs best with a 9:1 A/F ratio and gasoline with 14.7:1 ratio. E-85 carbs have jets in the triple digits.

You may think it's running right but I'm betting you have other problems.
 
in a stock low compression engine designed to run on unleaded fuel 87 octane should be fine
 
jar84203 said:
Doesn't ethanol absorb water which is bad for the steel parts in our vintage fuel systems?
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Yes it does and eats seals, floats, needles and seats too. Many fuel pumps are also not rated for e-85.

Ideally a street engine built for E-85 should be running about 12.5:1-13:1 comp ratio and have a fuel system set up just for E-85 with an e-85 specific carb and fuel lines and a fuel pump that are rated for alcohol. A lot of SS braided line isn't even rated for alky. A ss tank or fuel cell would be a good idea too. Also, you never want to let alky sit for long periods of time as it's way more corrosive than gas. Fuel should be drained if it's going to sit for more than a couple of weeks.

On the other hand, it's a way cheap way to get 105 octane fuel and a tremendous amount of power can be made on it, even in boosted applications. It burns cooler and is easier on parts, but you'll use a lot more of it (about 33% more).

My apologies to the original poster for getting off topic.
 
i just whenever i fill up with regular unleaded i throw in the stp gas treatment evreytime. i can watch the rpm gauge and tell u when that stuff starts going through the fuel lines in stead of 900rpm it goes to 975-1k
 
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