Premium versus Regular

subaru

#1

What do you think?



Is premium a ploy designed to add to Big Oil coffers? Or, do you think it’s a “must” for all high-compression engines, no matter what we said?



Want to chime in with a second opinion on something else we said? (It wouldn’t be the first time. But you probably already know that.)



Tell us what you think – and thanks for joining the discussion!



Tom and Ray


#2

Easy to see for yourself sirs. Go get a high-compression car that says “premium gas only,” and fill it with 87 octane. Watch your power go through the floor as the ECU desperately retards the timing to keep the engine from tearing itself up :wink:
Or get an older one without a computer that does that and listen to the pinging coming from under the hood :wink:

Is it a must in a modern high-compression car? No, I suppose not, as long as you’re OK with significant power loss as a result. Myself, if I just spent all that money for a whoop-de-do go fast car, I don’t want to be artificially slowing it down by putting lower grade gas in it.

And this is a good time for someone to insert the standard sermon: Higher octane gas does not = higher horsepower. If your car is designed for regular, putting premium in won’t turn it into a race car. Premium only has an effect on your power when you’re using it to prevent the computer from reducing power to avoid engine knock.


#3

Well premium is a ploy my the oil marketing companies. Even the name “premium” is part of the game.

They infer, in every way possible that “premium” is “better” than regular. However premium in a car that does not need it is at best a waste of money. How many times have you seen tthe adds that infer that premium has more power or will give better mileage (in all gasoline cars) than regular?

Premium is the right choice for those cars that need it or can take advantage of it, but it is a total waste of money for all the rest of the cars on the road.


#4

“premium gas only,” …the ECU desperately retards the timing

I don’t believe that the cars specifying premium only have the retard timing feature, only those that “recommend” it do that.


#5

ive had some vehicles that wouldnt run right on anything less and some that only run right on reg,depends on the vehicle.so their is a difference.


#6

It all depends on the car. Read the owner’s manual to find out what you should use.

If the manual specifies premium only, don’t use anything less. (In an emergency, you can put in a little bit of regular just to get to the nearest station that sells premium.)

If the manual recommends premium, but says you can use regular, too, you will find that performance, including gas mileage, is better with premium. It may be enough to wipe out the price difference between premium and regular.

If the manual specifies regular, using premium won’t do any harm, but the car won’t perform any better on it than it does on regular. Here, using premium is completely a waste of money.


#7

The reason many cars use premium is for higher performance. Putting regular in a car that calls for premium is the wrong answer. You may damage the engine and will certainly loose performance.
The right answer to save money is to look for a car that runs on regular like a Honda Fit our most non-performance oriented cars.


#8

My pet peeve is that the octane level of regular, mid and premium varies from state to state. My owner’s manual says to use 86 octane gas. In Colorado where I live, regular is 85 so I have to buy mid-grade which is 87. In Michigan, where I grew up, Regular is 86 so I could use regular if I lived there. Why is there this disparity between different states? That’s what I would like to know.


#9

Dear Sir, ALL cars built for sale in the U.S. Have had some form of “ignition retard” and have since the 1990’s. Some as early as the early 1980’s. (Even Chrysler K-Cars!) Check it out!


#10

Don’t forget that there are two methods of measuring octane and they don’t give the same numbers. Generally in the US the posted number is the simple average of the two methods.


#11

O.K. Start by takeing any basic automotive engine course and pay a lot of attention to the parts that talk about compression, power, timing advace, and detonation. Then try rewriting this little fable of ypurs.


#12

I own a 2006 Mini Cooper with an automatic transmission. I tried a full tank of 87 octane instead of the recommended 91 octane. The car turned into a SLUG. The car has only 116 horses to start with and it seemed like it lost 40% of the power! After two tanks of Premium 91 octane, the power came back. Merging onto the interstate was scarry with the 87 octane on board. So - I guess if I was CHEAP I would have bought a Chevy Aveo for $14k instead of a sporty MINI at $20k. Moral of the story is that if the car is designed for 91 octane, you only get the performance you paid for by putting in 91 octane.


#13

The reason many cars use premium is for higher performance.

Note to cclarify: Car manufacturers make high performance engines usually by increasing the compression and that in turn requires high octane or retarded timing which would eliminate the performance advantage. So just to clarify things, it is not the premium that produces the increased performance and it will not provide any performance gain in normal low performance engine.


#14

As I’m sure others will bring up, altitude also affects octane requirements of your engine. At a higher altitude, air is thinner, so you pack less of it into your cylinders, effectively resulting in a lower compression ratio. As a result, your engine’s octane requirement is lower at higher elevations. That’s why regular is a lower octane in Colorado, and your car should do just fine on it, without making the oil moguls that much richer. (Disclaimer: May not be true if you have a turbocharged or supercharged engine).


#15

My brother-in-law just bought Pontiac G6 hardtop convertible and asked me about Top Tier Detergent Gasoline. Yep, there is such a thing. Is it important to buy fuel only from these suppliers?

http://www.toptiergas.com/


#16

It’s probably all a scam by the oil companies with a lot of help from the auto manufacturers, but why has my stock '98 5-spd Neon always run better on premium?


#17

My '03 Jeep GC Overland with 4.7L HO V-8 runs fine on regular fuel, altough the mfr recommends Premium. Does the computer constantly adjust the timing to compensate for lower octane? Am I doing any long-term harm to the engine? My mileage is mostly highway with little load on the powertrain. Thanks…

JB


#18

Many of my friends put premium into their regular cars…waste of money. I can run 87 octane in my 87 Porsche 944S which requires 90. Knock sensor takes care of it…slight loss of power in my opinion, but my brother notices no difference when he borrowed it and tried both octanes. My daughter’s 94 Galant pinged on 87 (87 okay per manual) and it failed NOX emissions. No pinging on Premium. Base timing was too advanced, set it to spec, passed emissions, doesn’t ping on 87, but runs like a normal 4 banger. Ran like a scared rabbit before. On my old cars, I set the timing so I can use regular, but I was using premium in my 57 Thunderbird until the premium last tankful lifted the decade old paint where it spilled out the filler. Also took the paint off the fuel filter on the Galant when I changed it. Some additives! I wont’ mention the brand…the boys at the local Speedway may not like it.


#19

I have WRX (turbo). Will running regular gas kill the turbo. I drive 40-50K a year and would love to save some money. Thanks for the replies.


#20

I am anticipating getting a new car, and I would like to see more posts on emission affects upon using lower octane fuel in a higher compression engine which “recommends” high octane fuel. Some people have told me that lowering the octane will result in a “gummed up” engine with time.