What's the difference between premium and regular gasoline?

Question

We own an '04 Subaru Ouback H6 Anniversary edition. The dealership insists only putting premium gasoline in the car to prevent a knocking (?). However, some mechanic friends I know say it bs, but they don't specifically know about that type of car. Is there a difference for cars with high compression engines like my Subaru, or should I start going with lower grade gas?

Answer 1

There is virtually no difference between premium and regular EXCEPT---
Octane rating. All the additives are exactly the same.
There is no more energy stored in premium than there is regular.
Premium (92 octane) has more anti-knock compound in it than does regular (87 octane). That's the ONLY difference.
In the old days, we would advance the ignition timing by 4 or 5 degrees to get a bit more seat-of-the-pants performance, but it would cause the engine to "ping". To help combat this, we would use premium fuel.
You should use the fuel that the OWNER'S MANUAL recommends, or the label on the fuel filler door.
The engine's computer will adjust for knock. When the engine pings or knocks, there is a sensor that listens for that, and will retard the timing advance and initial timing until no knock can be detected.
For a clearer understanding of octane, go here----->

http://auto.howstuffworks.com/question90.htm

Answer 2

93 octain will ignite quicker/easier then 89 octain..

but ironically... if you use 93 octain in a car that is supposed to take 87 or regular unleaded. You might not get as good gas miledge or performance

it all has to do with when the fuel ignites, some cars need a quicker burning fuel.

Don't fall into the notion that the higher the octain the better, because that is not the case. You engine is tuned to map a certain air to fuel ratio mix and ratio and if you throw that off the engine has to compensate to fix the problem.

Use what your suppossed to use, however most new cars I'm told from a very good mechanic. Is that new cars can use the lower octain fuel.. If it says premium I'd just use 89, no harm done.
And your car has a knock sensor.. it won't let your engine get messed up, if anything you'll get less power and then, well use the premium...Cars today are smart and are computer run, cars have lots of safeguards built in.......

This was actually reomended for my 97 Mercedes .. it was supposed to take premium but with that car, it had issues of carbon build up and using the 89 vers the 93 was a solution.

......SUM IT UP... USE 89 and you'll be fine...

Answer 3

High performance engines require higher octane gasoline. Premium gas has a higher octane rating than low or mid-grade gas. When you go to the gas station you will see the octane rating on a little yellow sticke by the pump nozzle for that grade of gas. If you use fuel that is lower octane than what the engine requires then the engine will knock. Despite what others may say, the knocking from low octane gas can conceivably do damage if you use the low end gas on a regular basis.

I recommend using what is specified in the owner's manual; for example, the engine in my Corvette is optimized for 90 octane or higher gasoline, so that's what I use. Anything lower and it will ping. I also try to use better brands of gas like Mobil, Shell, Chevron or BP whenever possible...different brands have different formulations and additives in them, and off-brand "gasohol" mixes in particular have extra additives (to make the alcohol/gas mix burn hotter) that can be potentially damaging to the fuel delivery system, particularly the fuel pump.

So check the manual, and use that octane or higher fuel.

Hope this helped.

Answer 4

Check your owner's manual to find out the grade of gasoline and octane level that is recommended. If premium (93 octane) is recommended, your car will knock if you use regular (87 octane). However, if the owner's manual recommends regular (87 octane), using the more expensive premium (93 octane) will not make it run better; it may actually run worse. The owner's manual is the best place to check on the type of gas you should use.

Answer 5

on a stock engine its fine to run a cheap gas most car manufactures tell you to run a cheaper grade of gas the engine will only knock if its a high compression engine then it needs a higher octane gas in it as long as you dont here a pinging or knocking sound when you accelerate regular gas will do just fine regular gas is good for about up to 9.20:1 compression that engine is far from that

Answer 6

Basically it has to do with octane, premium has a higher rating than regular. Read you owners manual it will tell you what to do. My car for example requires premium but in the owners manual it does state that mid grade or regular can be used but performance will suffer.

Answer 7

the engine will produce more HP and run better with more octane...it may prevent knocking, some high-compression engines need it

Answer 8

About 10cents a gallon! :-)... Actually I had a Saab that required premium gas, if I put anything but in it, it ran horribly! and at one point blew the catalytic converter? about $700! 10cents a gallon, or $700?

Answer 9

listen to your car company! they know what they are talking about. if your car uses regular, use regular! if your car needs premium, use premium! dont try to down grade your car it's not worth it! and also you can't upgrade. so if it said regular on your car, use regular or your will waste your money!

Answer 10

premium is 98% octane and regular is 95%