What type/octane

[Jeff_DuBois]

Hello all, was wondering what type of ,and octane of, gas do you put in these older engines?. Do you buy the lead suppliments/ octane boosters?. Will modern gas destroy the valves/ carb gaskets?. thanks.

[Plymouthy Adams]

straight pump gas elcheapo if you like..these were not on a a high octane diet ever...these engines already have hardened seats...they do not like the alcohol due to old rubber in pumps etc..this gas today is short sotrage gas also..no lasting quality it seems...very gummy residue...

[TodFitch]

Ditto what Tim wrote:

1. Cheapest gas you can find.

2. No additives needed

3. Replace all fuel system rubber components (flex hose, fuel pump diaphragm, etc.) with modern materials.

4. Drive it.

On very hot days you may have a slightly higher tendency for "vapor lock" when running gas with ethanol in it, be sure your fuel pump heat shield is in place and that your fuel line from the pump to the carburetor is routed properly.

[Rusty O'Toole]

If the car was made before 1955 it was made for low octane low lead or no lead gas. Chrysler product flathead engines came with hardened valve seats from new.

The general rule is, the octane should look like the compression ratio. So if you have a mini van with 8.7:1 compression, use 87 octane. If you have a Corvette with 9.2:1 use 92 octane.

Old cars from before 1955 have compression ratios of 7.5:1 or lower and will run happily on 75 octane gas, which is lower than the cheapest regular available today.

Naturally this is not an exact rule, just a guide. There is some leeway depending on the car and the quality of gas.

Some real old timers with compression of less than 5:1 run best on a mix of kerosene and regular gas.

It is advisable to add a shot of Redex, Marvel Mystery Oil or some other upper cylinder lubricant. This is to protect the rings, pistons and cylinders. The old long stroke engines have a high piston speed and are more prone to wear in this area than newer cars.

And of course if you do not use the car very much, add some stabilizer to prevent the fuel going bad especially during winter storage.

[Todd B]

I disagree. I have found that Shell premium makes all of my old trucks run the best. In a pinch I have tried other brands and I always get a, what my dad always called a (spark knock) when ever you are under power such as going up a hill or pulling a load. There is clearly a difference. I have found that Citgo has the crapiest fuel. I own a 1988 GMC one ton dump truck that I bought new. Almost always my carbuerator would freeze up when I plow with Citgo fuel. Never happens with Shell.

My Observations.

[Don Coatney]

It is advisable to add a shot of Redex' date=' Marvel Mystery Oil or some other upper cylinder lubricant. This is to protect the rings, pistons and cylinders. [/quote']

Upper cylinder lubricant? Can you tell me exactly how any of these products do any good for upper cylinder lubrication? What lubrication is required in the "upper" cylinder? Lubrication comes from below. I think these products burn up and are expelled out the exhaust pipe. Can you show any quanified proof that these products do any good? How did these engines run for all these years without this ring, cylinder, and piston protection?

I have said this many times. Buy your dog a diamond studded collar and the dog will not care. But if it makes you feel better then spend your money on the diamond studded collar. Same with Redex, or Marvel Mystery Oil or any other magic snake oil product. If it makes you feel better then spend your money.

[Rusty O'Toole]

With all your experience of Dodge flatheads you should know they wear the rings and taper the cylinders faster than a modern engine. I put this down to the type of rings they used and the high piston speeds of the long stroke engine.

On your car this may not apply as you have modern rings and have rebored the cylinders.

But if I had an original engine I would consider it cheap insurance.

Or, if you want to add something to the gas, Redex or MMM makes more sense than octane booster.

[greg g]

Automotive engineers spend a lot of time and money desigining systems of rings and seals expressly to keep oil out of the combustion chamber of engines. Keeping those areas expressly free of lubricant, as they and we know that oil in the combustion chamber is not a good thing to be burning, and spark plugs especially do not like oil when spec'd for 4 cycle operation.

When engines wear out and rings and seals fail, and cars begin to smoke, and burn oil we usually A) put up with it, add some heavy oil to make it passage into the cylinders more difficult, C) sell the car, or D) rebuild the engines.

With that in mind how does introducing oil directly into the cylinder all nicely airiated and mixed with a fuel charge do any more for the combustion chamber than that which sneaks in past the rings and seals, new or worn?

Aren't the main ingredients in MMM (and others) petroleum distilates, stoddard solvent and mineral oil, isn't oil the item with the least volume in the mix? And mixed with the Distilates solvent how much is left after combustion to lubricate much of anything least of all a piston and rings moving rapidly away from it???

Edited September 6, 2011 by greg g

[Rusty O'Toole]

Automotive engineers spend a lot of time and money desigining systems of rings and seals expressly to keep oil out of the combustion chamber of engines. Keeping those areas expressly free of lubricant, as they and we know that oil in the combustion chamber is not a good thing to be burning, and spark plugs especially do not like oil when spec'd for 4 cycle operation.

When engines wear out and rings and seals fail, and cars begin to smoke, and burn oil we usually A) put up with it, add some heavy oil to make it passage into the cylinders more difficult, C) sell the car, or D) rebuild the engines.

With that in mind how does introducing oil directly into the cylinder all nicely airiated and mixed with a fuel charge do any more for the combustion chamber than that which sneaks in past the rings and seals, new or worn?

Aren't the main ingredients in MMM (and others) petroleum distilates, stoddard solvent and mineral oil, isn't oil the item with the least volume in the mix? And mixed with the Distilates solvent how much is left after combustion to lubricate much of anything least of all a piston and rings moving rapidly away from it???

Years ago they designed rings to allow a controlled amount of oil past them to lubricate the rings and pistons.

You can do as you please. A small amount of oil in the gas can't hurt anything.

[Don Coatney]

A small amount of oil in the gas can't hurt anything.

Will hurt my bank account. Why spend money for something not needed that will foul the spark plugs? As I said show some quantifed data for this snake oil.

[greg g]

A small amount was engineered for, but marketing guys decided that more was better, and they just happen to be in the business of selling the more part.

by the by the MSDS for Marvel Mystery Oil contains no mention of oil.....

Mineral spirits, Napthanic hydrocarbons (used primarily as an ingrediant in oilfield drilling muds) and Chlorinated hydrocarbons,(a boiling point modifier) are the ingredients listed there.

I think the can of MMM I found in my fathers garage, will stay on the shelf as a reminder of the quaint past, along with the can of Whiz knee action fluid.

Each to his own, as they say.

[Scruffy49]

When I have to move my 69 Dodge I prime the carb with 2 stroke mix. Lights right off, straight gas it backfires like crazy. Plain old basically stock 210hp LA318 with a 2 barrel and true dual exhaust.

My 98 Suzuki motorcycle runs best with an ounce or two of ATF mixed into the gasoline. 652cc single cylinder 4 stroke.

Maybe the oil counteracts some of the bleah factor from the ethanol in the fuel. All I know (or care) is that those work for those 2 toys.

Last time I fired up the 49 it managed to touch off the fuel residue from 1974 that got softened up in the fuel tank. A couple gallons of L'il Stinker (Idaho fuel chain) super high test (could still buy 100 octane then), 20 year old tank residue, hot 12v battery...

If you use an outboard spec Champion J6 these old flatties will burn 36:1 2 stroke mix. That's all we used to run in a 201 powering an irrigation pump.

[moparmonkey]

Marvel Mystery oil is pretty good at freeing stuck parts and dissolving gunk and deposits. I use it to soak stuck pistons. But its not a lubricating oil, so I don't see how its supposed to help your rings.

As far as the octane, all that is required is that the engine doesn't detonate. With a compression ratio at 7.5:1 or lower, you can run just about anything you want and not get detonation. 87 octane is far better than what's needed, and even with the ethanol we probably have higher quality fuels than in the 50's, certainly more consistant (ie, better quality control).

If running premium makes you feel good, then feel free. But hopefully you have stock in whatever oil company you buy fuel from, 'cause that's the only benefit you'll see from doing that.

[Plymouthy Adams]

if a person should have his timing a bit advanced the higher octane would be beneficial to prevent pinging..light throttle ping is also an indication of too much vacuum advance on a improperly tuned distributor...I still think it is funny that they make the higher octane less flamable and charge you more for it.

[Jeff_DuBois]

Thanks for all your input.

[Rusty O'Toole]

A low compression engine will run better on low octane than high octane gas.

[dmulhall]

I run everything I have with premium (lawn mower, snow blower, chain saw, minivan, pilothouse, 94 chev 3/4 ton) just because my mileage increases about 2mpg that makes up for the price. Not only that, but my fuel tanks don't rust out, fuel lasts longer in a jerry can and my small engines start so good after sitting for awhile.

I could care less either way, but in my brief time apon this earth, that is what is working for me. However I do buy my gas from a gas station where I do know the owner and I know it is premium. I believe 80 percent of the companies put the same crap gas in all their tanks then sell it out of a special hose for more money.

Just my 2 cents

[TheMoose]

A low compression engine will run better on low octane than high octane gas.

Read this and remember!

High octane fuel is HARDER TO IGNITE than lower octane gas.

That is so there is no pre-ignition or detonation in high compression engines.

If you run a higher octane than is required you are wasting your money & hurting performance!

[Robert Horne]

A low compression engine will run better on low octane than high octane gas.

My 20 year old Goldwing gets 48 to 50 MPG on low octane, and 40 to 42 MPG on high octane....

[Don Coatney]

I run everything I have with premium (lawn mower, snow blower, chain saw, minivan, pilothouse, 94 chev 3/4 ton) just because my mileage increases about 2mpg that makes up for the price. Not only that, but my fuel tanks don't rust out, fuel lasts longer in a jerry can and my small engines start so good after sitting for awhile.

I could care less either way, but in my brief time apon this earth, that is what is working for me. However I do buy my gas from a gas station where I do know the owner and I know it is premium. I believe 80 percent of the companies put the same crap gas in all their tanks then sell it out of a special hose for more money.

Just my 2 cents

The single most inportant thing is that by using the high octane premium you feel better. As long as you do, nothing else matters.