Engines that get better mileage with higher octane do so because the lower octane triggers the knock sensor and the computer pulls timing. You run higher octane fuel and you keep the timing advance without pinging. The extra mileage doesn't come from the fuel so much as it comes from the timing. Higher octane fuels are generally made from better base stock though, so they are a higher quality fuel.

 

The 87 is actually more expensive here for me in Iowa...but that's what I'll use, and a little lucas. Then maybe ethanol blends

 

I use 87 in my car, which is a DD of about 30 miles toatal on average day. engine was rebuilt a while ago though. havnt had any problems with it. it seems to run best on 76 brand though.
ive seen a couple signs advertising "100% gas" around here. aparently theres been a fuss raised over the ethanol having to be like 10% of gas these days hurting fuel mileage.

 

The e85 you need a special carb that's pricey and you can only use e85 then.On the lead substitute i have heard some people use it and some say there's enough lead built up on the valve seals to not worry about it.87 octane is enough for most cars on the road.

 

i do 87 octane & redline lead additive. its a '65 289 2V engine.

redline only takes 1 oz to 10 gallons of gas, its about $10/bottle after shipping but is a 12 oz bottle. i figure thats cheaper then the $2.50/bottle stuff tha you dump the entire 12oz bottle in each time.

 

i run the 10% blend in all my cars, havent ran into a problem yet.

maybe in theory the ethanol is hurting the carb or engine. but it runs fine.

 

E85 is 80% ethanol normal gas has been 10% ethanol for years its fine.

 

OOPPPS sorry guise i was being dumb.

 

i run 91 octain just because my car seems to start and run better with it. i really need a good tune.

 

E85 will hurt your engine if you have not tuned for it. By definition, it is a leaner fuel which requires more fuel per unit of air than regular 87 gas does. If you are tuned for 87 and run E85, you will run lean which is bad.

As for lead substitute, that is going to depend on whether you have hardned valve seats. If you do not, you will need lead additive.

As for octane, that is going to depend on your timing, cam, and compression. If you run higher compression or higher timing, you are going to need 91 or better octane gas. I run 10.5:1 compression, a little cam overlap, with 36 total * of timing, and it pings a little when it hits 100 around hear on 87 octane. 91 usually knocks it out.