Octane?

[Dracofrost]

I am currently lacking an owner's manual... what octane would be optimal to run in a first gen Toro? I've been running premium, which is 91, but I wonder if I should add some octane booster on top of that. What was the 425 Rocket built for?

And would lead substitute be a good idea?

[MattKing]

I'd try running 87 or 89 in your car while listening for spark knock if the expense of premium bothers you. If you get spark knock, back off the timing a degree or two. Don't waste your money on octane boosters-at best, they will do absolutely nothing for you.

I wouldn't sweat a lead substitute unless you run for hundreds of miles on the freeway loaded down to max capacity. Your Toro predated the government mandated exhaust catalyst, and as such it was designed to run on leaded fuel. Though it has been debated to great length, modern lead substitutes don't work particularly well. If you are really concerned with it, track down a municipal airport that will sell you a few gallons of 110LL aviation fuel. It isn't cheap. Mix a gallon into a tank of gas and sleep easy at night.

[Schurkey]

That'd be "100 octane Low Lead". Pretty blue gasoline, smells wonderful before AND after combustion.

'Course, it'll make your kids retarded if they sniff too much.

In the end, use the LOWEST octane fuel you can that DOES NOT produce spark knock.

[sharkeymark]

Too late the kids are retarded, LOL just kidding!!!

[ramair]

Hi, I would rather error on the side of caution and use the highest octane you can buy. Here in California that would be 91 octane. These cars were made to run on 97 with lead. I would start with a factory spec timing check with vacumn advance plugged. Fill the tank with the gas you are going to use, then take a friend along with you and test car on light acceleration near highway speeds. The reason for having a friend along is having an extra set of ears. I have a certain level of hearing loss (my wife thinks it is a selective hearing loss). If your car has a slight ping noise you need to retard timing 1 or 2 degree's. Keep in mind that as you retard timing you will create more heat at low engine speeds. The other option is to use a product like 104 octain boost. It is kind of pricey for everyday use , but it is cheaper than engine damage. These engines left the factory with 10.25 to 1 compression these engines can not be allowed to knock or you will damage the top of the pistons. The 4 most common ways to kill a Toro engine would be 1# loose timing chain or damaged cam sprocket, if cam jumps enough teeth valves will kiss the top of the pistons. 2# overheat engine and cause warpage or piston will lock in the bore. 3# spark knock by low octane fuel or advanced timing. 4# antifreeze in the engine oil either from leaky head gasket or intake manifold gasket, this will cause engine bearings to be destroyed. Michael TOA 691#

[Schurkey]

These cars were made to run on 97 with lead.

Perhaps, but that would have been with a different rating method for the gasoline. Just like how Europe currently rates the octane level of fuel today.

European octane level is "about" four or five numbers higher than US octane ratings. Europeans today--and USA "way back when" used Research octane numbers; while the numbers displayed at the pump in America today are an average of Research octane and Motor octane.

97 octane fuel "back then" would be about 92 or 93 octane today.
http://en.wikipedia.org/wiki/Octane_rating

GM was conservative about octane needs; the fuel specified was always high enough in octane that it shouldn't ping in a mildly carboned-up combustion chamber. Keep your combustion chamber clean and you should easily get by with slightly lower octane level.

You are correct, you do not want "ping" or "knock" due to low octane under heavy throttle. Short bursts of Ping or knock at LIGHT throttle was said by GM to be "The Sound of Economy". It hurts nothing but I for one would be happier if I did not have even that much ping/knock.

[68 Toro]

My engine had ping/knock under certain loads (acceleration, or going uphill). This was despite using premium gasoline. For the past few months I've been adding a bottle of Gumout octane boost with every fillup. Knock/ping has disappeared. It costs about $5 per bottle. Recently Advance Auto had a sale: $3 per bottle. I bought 20.