Just to put in my 10 cents worth, my 2015 Jeep Cherokee 3.2 V6 has a compression ration of 11.7:1 and the owner’s manual specifies 89 Octane. I actually posted a question (FUEL OCTANE, GENERAL DISCUSSION) here asking if the fact that I had been using 87 octane fuel was causing a problem. The consensus was that it was not.
@jtsanders My dad was teaching in a state college in 1938. His salary was $2500 a year. He hadn’t earned his doctorate at the time. He bought a new Chevrolet for $625 about 1/4 of his salary.
I started teaching at a state university in 1965. I didn’t have my doctorate at the time. My salary was $6000 for the year. My dad told me my starting salary was much higher than his starting salary. Yet, he bought a new car for 1/4 of his salary. I couldn’t buy a new car equivalent to his Chevrolet for $1500 in 1965. I did manage to buy a 1965 Rambler Classic 550 (the stripped down model) for $1750. It had 7000 miles on it, but I got the rest of the warranty. A couple of years ago our son began teaching at a state university. His starting salary was about $40,000. There is no way he could purchase a new car equivalent to my dad’s 1938 Chevrolet for $10,000.
The 2¢ a gallon I saved by running Sunoco 190 (sub regular) made a difference in the late 1960s and early 1970s.
My parents lived through the depression and really had to watch their expenses. It rubbed off on me and I have always watched my pennies. Now, my son is following the family tradition and has to watch his expenses.
I watch gasoline prices closely. A week ago, gasoline had been $2.02 a gallon for regular. The next day, it shot up to $2.55 a gallon for regular. I was at half a tank when I saw a station that hadn’t raised its prices. I pulled in immediately and filled up the tank. Half an hour later, that station went from $2.02 to $2.55 a gallon. I saved over $5.00 for half a tank of gas. I think about the savings I make by having vehicles that don’t require premium. A 15 gallon fill-up is a savings of $6.00 over premium.
Our gas prices here ar in the mid to High $2.40s for reg. The main store my wife grocery shops at give gas points for how much you buy in groceries, we usually get 40 to 60 cents a gallon off and you can buy 25 gallons. So we save $10 to $15 each time.
Modern cars that on;y require regular don;t get any performance boost from premium because the computer sets the timing. That was not always true.
I had a 56 Desoto with a 330 cube hemi that only required regular, but I advanced the timing 6 degrees and used 102 octane Amoco which was unleaded and used one heat range colder plugs because I always had my foot in it. I used the Amoco because the hemis had a tendency to lead foul the plugs. It gave a very noticeable increase in power.
As far as the 40 cent difference in price, it depends on how a business allocates it’s costs. Do you allocate your cost at the same price for all the products you sell at a fixed cost per gallon for the two tanks required for gasoline, one of diesel, one of kerosene and one of ethanol free 91 octane. A case can be made for charging a higher price for products that require their own tank even the sell product in much lower numbers.
One of the most destructive accounting practices in the trucking industry was terminal cost accounting where each terminal was judged on its own costs. Say a set of trailers comes in from NY City to Buffalo for fuel and a driver change to leave for Chicago. Someone notices paint or worse yet acid running out under the sealed rear door. The right thing to do would be to break the seal, save as much of the other freight on the trailer , notify Hazmat and clean up the mess. That is not what happens, the cost of fueling or changing tractors is borne by the road operation which is not charged to the terminal. Once you break the seal and work the load, the cost is accounted to the city or in some cases the break-bulk operation of the Buffalo terminal.
That trailer is going to go down the road with its seat intact even though it would save the company money to limit the damage as early as it can.
Some companies put everything on a fixed per ton mile basis and will not take freight that does not pay enough to exceed that cost. That sounds intelligent until you consider the that trailer will have to run empty to get to a location that generates a lot of freight. Per mile accounting doesn’t differentiate fixed costs like insurance, costs of terminals, registrations , costs of buying equipment, from operating costs.
The reason they say premium gas only is that the engine is going to detonate with lower octane grade of fuel. Detonation is destructive of high compression engines. It burns valves, piston heads, head ports, etc. i.e. anything that is exposed to heat of combustion. Detonation is explosion rather than burning in a controlled manner. Stay away from detonation which may not be audible and pinging which is.
I read a account of a twin engine airplane that was fueled with Jet A, very detonation prone in a piston engine. On take off one engine then the other failed causing a crash. When the NTSB examined the engines, they found pistons burnt through, burned and torched valves, and general heat damage to engine. Case in point.
Are you finding this to still be a problem? It has been twenty years since I have had to deal with spark knock complaints from customers and those were on trucks without knock sensors. Cars have knock sensors and the complaint of detonation has been very rare in the last twenty years.
The detonation may get the point where there is compression ignition. In which case, the combustion can no longer be regulated by ignition timing retardation. Usually modern ECMs limit detonation (spark knock) by retarding ignition timing which affects fuel economy. But, if you want high performance out a small liter engine, you have to settle for higher compression ratio. So either it is larger engine using lower octane fuel and lower compression ratio or a small size engine using a higher compression ratio and a higher octane grade fuel. No two ways about it.
I’d use Gulf because the location of a station was very convenient. They sold Gultane, Good Gulf, and No-Nox.
I always wondered if my 64 Beetle would run well on Gulftane, but I always bought Good Gulf (regular). I could fill the VW’s nearly empty tank for 3 bucks and I’d get a free drinking glass, too!
CSA
I’d submit that one reason might be that it’s hard to hear it anymore. Cars are much better insulated for sound - especially the ones that require premium, because they tend to be higher-end. I only really hear my engine when I’m accelerating enthusiastically. And mine will predetonate if you put regular in the tank.
I’m all for teachers getting better pay. Teachers salaries have not stayed up with the rest of industry over the years, so it’s tough to make those comparisons. Back when your grandfather taught $6,000 was considered high end of the pay scale…even for people with a college education. Your son’s $40,000 is a little more then half an average engineers starting salary. A fresh-out from a top college (Harvard, MIT…etc) with a technical degree can easily demand six figures.
@MikeInNH. I had my opportunities to earn a higher salary. My degree was in research design and statistics. A big corporation tried to lure me at a salary almost three times what I was being paid as a university professor, but I decided I would rather work with students. The big salaries at universities goes to administrators. I did apply for an administrative position, then decided I would probably become bored with the position, so I withdrew my application. I was then asked to resubmit, but I refused.
I had a chance of becoming the chair of my department. The man who had been chair for a quite a while died of cancer while in office. We brought in a chair from the outside. He lasted a year and a half and died of cancer while in office. A group of my colleagues wanted me to become chair. “Nothing doing”, I told them. “The last two chairs died in office. I know what you are trying to do to me”.
Today, with a young family, I probably would have taken a job where the income was better.
I still look for ways to save money. I won’t buy a car that requires premium fuel. I buy the house brand cereal at the grocery store. Like my car, I can run on regular. I am 77 and haven’t developed spark knock.
Depends on the university. My daughter did some research her last year at MIT. The full time professors at MIT can easily make over $200,000. A lot of it coming from research grants. But in general at most universities…college teaching salaries are low. Most teachers at colleges near here are part time - well over 70% with some as high as 90%. And a part time teacher salary is pitiful. We have a neighbor who teaches who’s a part time teacher at 4 different colleges. Luckily they’re all in Boston.
@MikeInNH. Many colleges and universities hire part time adjuncts. These part time people are paid per class and being part time, the institutions don’t have to provide health benefits. This savings allows the administrators to buy expensive cars that require premium fuel. I refused to teach an overload. The extra pay was a fraction of what I earned teaching a class that was part of my load. If I had a factory job, I would be paid time and a half for overtime, not a fraction of what I was paid for a class that was part of my regular load. Besides that, I knew the only way to advancement was to do research and publish, so that is how I invested my time beyond my teaching duties.
Don’t get me wrong–I loved my job. I loved working with students and I liked exploring new ideas with my research. I don’t see a conflict between teaching and research. One has to be s student exploring new ideas to be an effective teacher.
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Don’t kid yourself about mothballs. I got wiped out by a lady in a model-T using premium gas. What I didn’t know was that she was running a funny car with a 456 hemi. However, those were the days of lead/unleaded gas and before ethanol entered the scene. Ethanol can be used to raise and meet octane requirements. Premium gas may or may not contain ethanol depending on the requirements of the state that you’re in. Bottom line: I use what the manufacturer recommends to keep the warranty, and clean out my carburetor at least once a year.
You mean you spray carb cleaner in the throttle once a year, or you disassemble, clean, and reassemble the throttle housing once a year?
Ethanol’s (E-10) main purpose is as an Oxygenate to help gas burn more cleanly. MTBE was used until it was banned about a decade ago. We’re still finding that stuff in ground water.
The owners manual for the vehicle should explain the consequences of using other than the recommended grade of fuel.
I remember a Puzzler on Cartalk about some car that wouldn’t start after a sudden drop in temperature in the early fall. The owner had meticulously maintained the car, had it tuned up for the winter (new spark plugs, etc.) and filled the tank with premium gas. According to the puzzler, the problem was the high octane gas. The octane is the resistance to burning. It seems to me that regular gas would be an advantage to.starting a car in cold weather.
That’s news to me. 
Although it does that, secondarily, I understood that its main purpose was to enhance the profits of 
corn growers in the U.S. 
CSA
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You have a car with both a warranty and a carburetor? Please tell us what it is. Don’t think I ever saw a Model T Funny car or a 456 Hemi either.
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IMO, you are half right, CSA. E10 levels of ethanol do exactly what Mike said, and that is the prime purpose. While Mike didn’t mention it, ethanol also replaces MTBE, the previously used octane enhancer and a tenacious poison. Higher levels of ethanol, like E15 and higher, are income enhancers for corn growers. If E10 is so awful, how do you propose we enhance octane?
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