Unleaded Fuel Additive

[shipard]

Hi All,

Another quick question and please excuse the ignorance.
Do i need to add a lead additive when fueling up with 98 RON unleaded fuel for a 1972 2.4S motor, and if so which one do people use or recommend

Thanks

[Chuck Miller]

Clayton,

It would be a little easier to answer your question if we knew what part of the world you'll be filling your tank in....

However, we here in SoCal have the most additive infested, crapy, gas (especially in summer) in the lower 48 and I run 91 octane with a 9.5 c/r RS spec motor with no problem. I do add about a 1/2 pint of Marvel Mystery Oil in the gas and oil about every month.....

Cheers, and hope this helps

[72targa]

Cool! Something I know the answer to!! If your motor is stock, you're running 8.5:1 compression. You can run all day on regular gas (87 octane here in the San Francisco/Bay Area).

[shipard]

Sorry I should have mentioned I live in good old down under Australia

[72targa]

Reference:

http://en.wikipedia.org/wiki/Octane_rating

Quotes:

In most countries (including all of Europe and Australia) the "headline" octane rating, shown on the pump, is the RON, but in the United States, Canada and some other countries the headline number is the average of the RON and the MON, sometimes called the Anti-Knock Index (AKI), Road Octane Number (RdON), Pump Octane Number (PON), or (R+M)/2. Because of the 8 to 10 point difference noted above, the octane shown in the United States is 4 to 5 points lower than the same fuel elsewhere: 87 octane fuel, the "regular" gasoline in the US and Canada, is 91-92 in Europe.

In Australia, "regular" unleaded fuel is RON 91, "premium" unleaded with RON 95 is widely available, and RON 98 fuel is also reasonably common.

Thus, if your engine is stock (i.e. running 8.5:1 compression), you should be able to use RON 91 ("regular" in Australia). If you have pumped up the engine to a higher compression ratio, you will need a higher octane product.

[shipard]

Thanks Peter,

So if i use 98 Ron, on the standard engine is there any negative side affects or is that actually better for the engine ?

I say this as 98 is more efficient, I have used this in all my other cars with no negative side affects yet and it does actually get more kms/litre. Apparently it is also a high detergent fuel as well so it "cleans" your engine also.

If i use the 98 Ron in preference to the 91 or 95 Ron do I also need to add any additivies ?

Cheers

[rgrimm]

FWIW (perhaps not much) when I bought the '68 about 15 years ago, I asked my wrench about a lead (actually, lead-substitute) additive. As I recall, his comment was that it would be a little easier on the valves and guides, but if the engine has had any work done on it, the newer replacment valvetrain components really didn't need lead anymore.

So I started using an additive (only every other tankful) but when I found out the engine actually had a sustantial overhaul just a few years before I bought it (around 1990), I quit. Just burn the premium I can buy at our pumps (about 93) but still avoid ethanol on the classics. And in our part of the country, it is possible to pull up to the pumps at some stations and find nothing but ethanol blends in all the grades

[72targa]

Hi Clayton:

The quick answer is "only use the octane level your engine requires".

Our old cars, without modern computers, will let us know when they need higher octane. They will "knock". If the engine is under load and you hear knocking, you need higher octane. My 2.4S runs perfectly on regular unleaded as discussed above. If I used mid-grade or premium, my car would not really run any better. What would happen is that un-spent fuel would go out the tailpipe as the compression ratio is not "large" enough to fully make use of the additional octane.

If I had an earlier S with higher compression, I would need to use a higher octane fuel to correspend with the higher compression ratio (and to avoid knock). This is a great example of "more is not necessarily always better".

Modern cars with computerized ignition systems and knock sensors can make use of multiple grades of fuel/octane (but they are still optimized to a particular grade/octane).

As for ethanol, I must admit that I am scared of it. At 10%, it should not be significant but at 50% to 100%, I'm very leery of what it will do to our old fuel systems (because of its affinity for water). Any other experts on this topic out there?

Hope this helps.

[tomkirkcis]

Clayton,

It would be a little easier to answer your question if we knew what part of the world you'll be filling your tank in....

However, we here in SoCal have the most additive infested, crapy, gas (especially in summer) in the lower 48 and I run 91 octane with a 9.5 c/r RS spec motor with no problem. I do add about a 1/2 pint of Marvel Mystery Oil in the gas and oil about every month.....

Cheers, and hope this helps

ok Chuck, I will bite. In the gas as a top end lubricant and in the oil for what? Is this a common practice? > I have added Marvel to gas after the cat has been ibn storage, but not as a common practice. tom

[72targa]

There is not much to Marvel Mystery Oil. Studying the MSDS, one notes the following:

1) It's mostly naphthenic base oil and mineral spirits (better known as Stoddard Solvent and commonly used as paint thinner).

2) It has a small amount of 1,2-Dichlorobenzene ("Chlorinated Hydrocarbons"). This is normally used as a solvent for waxes, gums, resins, tars, rubbers, and oils.

Here's the MSDS:

http://www.turtlewax.com/res/msds/MM010-4.pdf

So, you basically have some solvents thickened with base oil.