Higher Octane than Regular gas....?

[p10plymouth]

Hi , New here old in the hobby.... I have a Stock 1940 Plymouth P10 4 door and have been using regular gas , Runs fine .... but was wondering if any body here tried using a higher octane gas... And can tell me if it made any . difference .... Thanks for letting me know ...

[Young Ed]

Sometimes when its in the 90s here I will go get the premium gas that doesn't have ethanol. Makes for better hot starts but I believe thats from the lack of ethanol not the higher octane.

[Don Coatney]

The higher the compression ratio the higher octane level required. Your engine if completely stock has a compression ratio of between 6.6 and 7.0. Upgrading to hightest is a waste of money on your car.

[martybose]

My mechanic said that my engine came out at about 9 to 1, and recommended that I run premium unleaded. While working through various carb and ignition issues, I definitely have detonated this thing more than a few times!

Marty

[Captain Neon]

I run premium fuel just because it is less likely to leave residue and run cleaner due to the chemistry of higher octane fuels and the cleaning additives in them. My P15 sees the road less often than my daily driver so it takes longer for a tank of gas to get used up. Just piece of mind, I suppose.

I really don't need the higher octane, but it makes me feel better to know that my baby gets the best. I've been running premium for over 15 years, and I think I may have saved myself a few headaches because of it.

[Plymouthy Adams]

higher octane..less flamability..so the higher the octane in the older low compression engine..the better your ignition must be...octane is an additive to retard burning...

[p10plymouth]

That's what I wanted to know! if High test ,is better, I also do not want just minimum for my car.. Thanks for the info!... I also do not drive my car a lot, and by adding premium , the cost is not the issue... I remember some old reports that said if you use to hightest gas it will flash, and not burn properly, But others said they experience smoother idle and no hesitations... and as others mentioned , a feeling of more reliability..

[48mirage]

I used to work for Texaco Refining and I worked on the Reformer unit where we made the high octane gasoline. It was actually blended down before going to the retailers. In our low compression engines there is no need to use high octane. As far as the additives they are splashed in after the tanker is filled. We sold gas to several different wholesalers. After the compartments were filled with gasoline they would pull forward to the additives station and depending on the "brand" for each compartment he would add that "brands" additive. The trick is to use a major brand name gasoline to get the proper additives to keep you engine clear of junk. I will not buy the wally world gas because like most everything else they do, the product is less than the best.

For those of you that ever buy gas in Missouri. All gasolines in Missouri must contain 10% ethanol by legislation. The legislature also removed the requirement that the ethanol content be displayed.

[Don Coatney]

I run premium fuel just because it is less likely to leave residue and run cleaner due to the chemistry of higher octane fuels and the cleaning additives in them. .

Can you give more details? Why is it less likely to leave residue? Why does it run cleaner? How is the chemestry different?

[Captain Neon]

Gasoline is a mixture of many VOC, but the main three are hexane, heptane, and octane. Longer carbon chains, hexane=6, heptane=7, octane=8, allow for smoother burn in an internal combustion engine. To keep it simple, higher octane numbers are achieved by an increasing ratio of octane molecules to hexane. The octane molecules are less likely to predetonate and burn cleaner, less carbon build-up etc. Premium base gas is also required to meet certain requirements before being added to the pipeline that regular gasoline does not have to meet, (there is not just one gasoline national pipeline, but at least two of differing grades) among these is a higher detergent concentration. As a general rule, anyone's premium gasoline will afford a cleaner fuel system and better performance than any one else's regular gasoline. The higher loctane may not snap your head back at acceleration, you may never hear the engine knock on the cheaper stuff, but at the worst one is just spending more money for gasoline. Premium pump gasoline may not do any good, but it won't hurt. Regular gasoline may or may not do any harm, but it could do more harm than premium. Racing fuel and octane boosters are a whole other situation and excessive use of these chemicals may be detrimental, but premium pump gas is not a problem.

[martybose]

The issues of cleaner additives and higher octane are usually completely separate from each other. As an example, I believe that essentially the same additive package is used on all of the Chevron gasoline grades. They won't confirm this, of course, and my "evidence" is strictly anectdotal. Before it met its untimely demise, I put 168,000 miles on my 92 Civic commute car running Chevron 87 octane, and never once had to have any injector service, while friends of mine running other gasoline brands had to have their injectors cleaned every 50-60K miles. I also found it interesting that Chevron was the only major brand that didn't have to reformulate their domestic gasoline to meet the new Euro standards, which emphasized long term life of fuel system components.

As far as octane goes, the conventional wisdom is you run the least octane that will run well without detonating. Very few of us are good enough to actually hear minor detonation. Our old cars are actually easier, since they are usually either okay or way off. it's much more difficult in a modern car, which often retards the ignition a few degrees if it detects an inaudible detonation.

As for the extreme octanes, I've used them too. One of the race cars I work on usually runs 114-116 octane leaded racing gas, which is truly vile stuff. But it is using 20 pounds of boost to make 350 horsepower out of 90 cubic inches, and always runs with a cooler exhaust temp with the higher octane fuels.

If your car runs fine on 87 octane, use it! YMMV, as always!

Marty

[Guest rockabillybassman]

As a side issue here, what do you call regular in the US? Here in kiwiville, regular is 91 octane, and super is 96 octane.

[Young Ed]

For me its 87 and 91. A few places carry a mid grade of 88-89.

[greg g]

Some places sell and economy grade rated at 86. While on this, I think the rest of the world uses a different rating scale than we do.

Research Vs Motor octane ratings

One value is the research octane number (RON), which is determined with a test engine running at a low speed of 600 rpm. The other value is the motor octane number (MON), which is determined with a test engine running at a higher speed of 900 rpm. If, for example, a gasoline has an RON of 98 and a MON of 90, then the posted octane number would be the average of the two values or 94.