It’s the government’s fault.
I really hope that was tongue-in-cheek!
Ah yes, this brings back memories of my '81 Subaru hatchback. My first new car, with memories of the '79 gas crunch still fresh, was a little econobox. Imagine my horror in going to the gas station for its first fill-up and see that 91 octane premium was required! At $1.45 a gallon! Who would have thought to ask what gas a cheap econobox required? I tried running with 87 regular a few times and it sounded like a paint can half filled with marbles in one of those shakers. Eventually I persuaded it to accept 89 octane with a very light foot on the gas. My lesson: always specifically ask what octane a car requires before buying it!
Was carbon buildup ever really a problem for a properly maintained car burning quality gas? I remember ca. 1970 my father taking the family car out on the Interstate in second gear and redlining it to “blow the carbon out”. I wonder if that accomplished anything, or had he just fallen victim to something his grandfather had passed on to his father…
I inherited a 1999 Park Avenue Ultra from my mother-in-law a few years back. First time I drove the car, it seemed like a slug, especially for a car with a blower. Then, not “knowing any better,” I filled it with premium gas, as the little sticker inside the fuel door ordered (not recommended; the sticker says “UNLEADED PREMIUM ONLY”). Woo-hoo! The car took off like it had rockets on the bumper! Seems grandma had been a bit of a cheapskate and always filled the car with cheap regular. Her son knew about this, but said that since the car had a knock sensor, running cheap gas wouldn’t hurt the engine, and besides, did we really want grandma running around in a hot rod?
Anyway, when gas hit $3 a gallon, I experimented with regular and mid-grade, and found that, as before, performance was miserable with regular. Mileage declined quite a bit as well. Then I tried mid-grade, and found that performance and mileage were still worse than with premium, though not as bad as with regular. Finally, I did the correct math: computed miles per DOLLAR rather than miles per GALLON, and found that it was nearly a wash; the lower mileage with regular almost cancelled out the cost savings. So, I’m back to premium. Running regular or mid-grade doesn’t really save me much money, and I like having the car respond when I tap the gas pedal.
“However, putting premium in a car that can run on regular can lead to carbon buildup and eventually the car WILL require premium.”
never heard of this before. Are you sure?
Anyone else comment?
I drove an Acura 3.2 TL for the duration of a 39 month lease. At first I used premium because the manual said I should and the fuel filler door said premium fuel only. When the price rose past $3.00/gal I spoke to the dealer and they said go ahead and use regular fuel and don’t worry about it. From then on I only used regular (87 octane) and I never noticed any difference in any aspect of driving the car, fuel mileage,performance, power, etc. Maybe it depends on the vehicle.
I have a 90 HP boat engine and it runs much better on premium gas. At low speed it just doesn’t fire right.
If your manual states to run higher octane why take the chance of engine damage by using 87 octane? Even if you engine will run on a lower octane than what is recomended, you are going to lose what you saved on the per gallon cost to lower miles per gallon. By the same token if your vehicle is recomended to run on 87 octane, and does not ping, then you are throwing away your money to buy the higher octane. A good tune up on any vehicle will help it run on the lowest octane recomended for it.
Combustion processes are complex physics. Higher compression ratios improve the mechanical effiency of the engine. Thus more power. However, pure gasoline detonates if subjected to high compression. Additives prevent the gasoline from exploding prematureley. The additives themselves are not combustible. This means that a given amount of “premium” gasoline has less btus/unit volume than “regular” gasoline. In some cases ignition retard can compensate but only within limits.
Retarding the ignition where compression ratios are close may help. However, combustion temperatures may rise offsetting the benifit. The best advice is use the fuel recommended for the design. There is no advantage to using “premium” in an engine that does not require it. In fact mileage suffers due to the loss off btus/unit volume. Higher compression engine suffer from lower “octane ratings” because the advantage of thermal efficiency is lost.
I think that on most modern cars the setup is such that the car will adjust itself to any type of gas so on newer cars I think it is of little importance. on older cars the timing can be adjusted to make low grade gas to work. I drive an 05 Mustang GT which has a high performance V8 and is also rated for regular and gets around 20 screaming miles to the gallon the best of both worlds I should say
The old premium vs regular debate!. Perhaps compression ratio should understood better. It is better to think of the compression as developed cylinder pressure. In a supercharged engine the mechanical compression ratio can be quite low, however, the actual cylinder pressure and therefore combustion chamber air tempurature at TDC can be very high. This why a supercharged engine with relatively low mechanical compression ratio requires higher “octane”.
So, all these discussions of actual performance are all well and good but I have not seen a comment upon the rising price of gas making the difference in cost for premium a smaller and smaller propotion of the cost of gas. When gas was less than $2.00 a gallon it was a gretaer than 10% increase in the cost of a gallon for increased performance. AT $3.00 per gallon or better in some parts of the country, it is a 6% or less increase in cost per gallon.
The question really is: If you own a high compression engine and you want the higher perfomance that premium provides, at what percentage of the cost of gas does the increase make sense? What price would gas have to be for the $.20 per gallon increase to be desirable?
The other question becomes: Why is premium ALWAYS $.20 more per gallon? Does it not make sense that the difference in price should rise propotionally for premium as the cost of gas increases? When gas shifted from $2.00/Gal to $3.00/gal shouldn’t the added cost for premium have gone from $.20 to $.30?
Enquiring minds want to know.
My answer to why buy a performance car and use less than the required high octane test? because I don’t need it. I have a Subaru turbo that replaced an Audi turbo. When I drive in places I need neck-snapping acceleration (I’m thinking of rallies or having to pass trucks and campers on curving mountain roads) I use only 91+ octane. For the intervening weeks upon weeks when I’m at work and my wife is only shopping the cheap stuff and the accompanying timing retard works just fine.
Can Mr. Clickie or Mr. Clackie or any of you Mr.Postie’s inform me as to how to ascertain whether any given petrol station is selling Tier 1 or Tier 2 gazzooleen?
Ken, hustling around a WRX STI
This is a good question, after the early postings on better mileage with premium. That 20 cent difference has tended to stay constant, so the cost advantages of using the regular should have fallen with increased prices. That is approximately the same differential as in France, however, and I haven’t seen a pronounced bias toward their 95 octane premium despite pump prices a multiple of what we pay in the US.
I’ve noticed the same thing. Think about it though - both regular and premium are refined from the same crude. The price difference is due to additives and the refining process (?). So if it costs .20 more to produce premium over regular when crude is $30 a barrel, and the same .20 when crude is $80 a barrel, the oil companies would be pulling a clever and deceptive marketing gimmick if they charged 20% more for premium instead of the $.20 cents more it actually costs to produce.
I have a 2007 Cooper S and have been putting regular in it, yeah i can feel a bit of a lack of power but not such a difference as you’re describing with the 2006 cooper. I don’t like the idea of grunging up my engine with lower octane though so i also add some stuff to my gas to help keep my engine clean. If i go race autocross, definitely putting the 91 in, but when i’m commuting to work the 87 has been working just fine and i’ve gone over 3000 miles since i’ve had it.
Most vehicles will run on regular, howerver those designated as requiring premium will sence when regular is being used and will “dial back” performance
to accomodate the fuel. Don’t need all the performance your “premium” car produces? Use reular and save money.
I don’t like the idea of grunging up my engine with lower octane though so i also add some stuff to my gas to help keep my engine clean. If i go race autocross, definitely putting the 91 in, but when i’m commuting to work the 87 has been working just fine and i’ve gone over 3000 miles since i’ve had it.
How much is that bottle of “miracle goo” running you? I bet if you run the numbers, you’re spending more on the goo than if you bought 91 all the time. Also, not to be a wet blanket or anything, but if the engine is damaged because you have been using the goo + 87 octane fuel, I doubt the factory warranty will cover the cost of the engine work.
Almost everyone, including Tom and Ray, assume that retarding the timing will avoid detonation. If you go back to your basic engine research, you’ll see that detonation can occur 'way down on the stroke…'way before any timing retard.