[bruin]

So which grade of gas do we *really* need to use?

From what I understand, older cars (more then 15 years) will knock like crazy if you put a lower grade then what is required for your engine. But today's modern engines have onboard computers that modify the timing of the engine to adjust to whatever grade of gas you put in it. So all you lose is some horsepower.

There is no point in putting a higher grade then what your car calls for, but what if your car calls for premium, like a Mercedes, and you stick in regular anyways? How bad is knocking for your engine?

[BrownDog]

Knocking is one of the worst things that can happen to your engine.

Having said that, you should always use the lowest octane rating that will prevent knocking.

[gnm]

Low grade in most places appears to be 87 octane but here in New Mexico it is 86 octane crap gas.

-G

[Tyler_JC]

My car "requires" mid grade according to the dealership.

But I've put nothing but regular in since I bought it and it drives just fine.

I'm losing a little horsepower, but it's not like I'm towing a boat or trying to win the Indy 500.

[basil_hayden]

Higher octane is for higher compression engines. No need to use premium if the manufacturer says regular is ok.

Higher octane prevents detonation in high compression engines. Knocking is a sign of detonation.

Detonation is like an explosion in the cylinder instead of just combustion.
Detonation blows up rings, pistons and cylinders, combustion does not.

[PhilBiker]

Higher octane is for higher compression engines.

Not necessarily. My moto has a compression ratio of 11:1 and the book calls for 87, which it runs perfectly on. It's not just high compression, but advanced ignition timing that causes the requirement for higher octane.

No need to use premium if the manufacturer says regular is ok.

Exactly.

[gego]

The manual on my auto calls for 91 octane. They have a ping and knock detector, but it requires the detection of those to adjust so the damage has already started.

Damage from knock is cumulative.

I checked online for their opinion of using lower octane and they warn against it because of the potential for engine damage.

It is not worth the risk to me for the difference in price.

Be aware that if your manufacturer calls for premium, you are taking a risk of damage using a lower octane and getting detonation prematurely.

[lotrfan55345]

If you want to save money and use a higher-octane gasoline, why don't you ppl just use an octane booster? They are like $4.00 for a bottle, and you only need to put in a few drops...

[Aedo]

So all you lose is some horsepower.

You also lose efficiency.

And as stated by BrownDog and gego knocking is bad news for engines

[PhilBiker]

So all you lose is some horsepower.

You also lose efficiency.

My wife's car calls for 93. it runs ok on 87 but the gas mileage nosedives. 89 is fine.

[richardmmm]

i always found that the savings on regular were replaced by loss of efficiency and gas mileage, plus the car becomes more of a dog to drive.

So I began to break the regular savings myth lately, and use premium.

Week to week it cost about the same, giving better mileage, but costing more. But the car drives much better and smoother and the purity is better for the engine.

I figure the whole thing is a con in the end.

It's like asking if you want to get drunk on whiskey or beer.

Sure a bottle of one costs more than the other but basically the end result and costs per night out work out to be about the same, and whiskey saves you a lot of time in the john

[bruin]

i always found that the savings on regular were replaced by loss of efficiency and gas mileage, plus the car becomes more of a dog to drive.

So I began to break the regular savings myth lately, and use premium.

Week to week it cost about the same, giving better mileage, but costing more. But the car drives much better and smoother and the purity is better for the engine.

I figure the whole thing is a con in the end.

It's like asking if you want to get drunk on whiskey or beer.

Sure a bottle of one costs more than the other but basically the end result and costs per night out work out to be about the same, and whiskey saves you a lot of time in the john

Less time in the john is a good benefit. I'll go with the premium.

[PhilBiker]

i always found that the savings on regular were replaced by loss of efficiency and gas mileage, plus the car becomes more of a dog to drive.

So I began to break the regular savings myth lately, and use premium.

Week to week it cost about the same, giving better mileage, but costing more. But the car drives much better and smoother and the purity is better for the engine.

I figure the whole thing is a con in the end.

It's like asking if you want to get drunk on whiskey or beer.

Sure a bottle of one costs more than the other but basically the end result and costs per night out work out to be about the same, and whiskey saves you a lot of time in the john

Bunk.

The whiskey or beer analogy is far too extreme. The difference in gas grades is more like skim milk versus 2% milk versus whole milk. All three are milk, all three are just as good, but one key ingredient is different in a very small, but important way (amount of fat). Is one better than the others? Depends on what you want from your milk. Want rich creamy taste? Whole is best. Want less fat? Skim is better. Want both? Get 2%. They're all just as good.

If the engine you're using is not specifically built to take advantage of high octane gas (many are these days, particularly performance cars) you're throwing money away and wasting crude (it takes more crude to make premium) by using it. Consult your owner's manual for the octane your car is made for. Most non-performance cars run perfect on 87. On my wife's sportscar the mileage suffers badly if we use 87. On my touring motorcycle and my car anything over 87 does nothing but lighten my wallet.

If your owners manual says that the car requires 87 and it runs better or gets better mileage on 93, something is wrong. It's probable that running the higher octane is covering up a problem somewhere that needs to be addressed. Get a tune up.

Most lawn mowers require high octane gas.

"Premium" or "super" or whatever are nothing but manipulative brand names designed by corporations to make you feel like the higher octane gas is somehow "better" than lower octane gasoline. Of course you want "the best" for your car, right? You're a sucker if you buy it and your car doesn't need it.

[redfire]

My 2002 Pontiac Grand Prix with the n/a 3800 V6 was designed to run on 87 octane which I use. Putting higher octane would just be a waste. Actually I think it gets a little better mileage using the 87 octane ethonol blended fuels. The car's pcm "learns" your driving style.

I do know if my car had the supercharged 3800 v6 in it, then the only way to go would be the high octane fuels, mainly due to knock requirements. It doesn't take very much to burn a piston if you get into a knock situation.

If you want to maximize the fuel economy, then follow these tips:

1.clean air filter
2.new spark plugs/ low misfire wires
9.new (clean) oil
4.yearly lube/cleaning of brake calipers
5.good working thermostat
6.automatic transmission fluid changes very regularly
7.coolant changes regularly
8.proper tire inflation
9.no excess weight in trunk
10.use cruise control on long trips
11. obey the speed limits
12.clean/washed/waxed car
13.radiator cleaning (outside dirt etc)
14.sensible driving/accelleration/braking
15.A/C use instead of driving with windows down

[lowem]

After some trial and error, I found that "mid-grade" RON95 Esso/Mobil works best for my 1997 Honda Civic.

The equivalent of "regular" over here, RON92, actually resulted in a decline in efficiency, because the 12-valve VTEC-E, or econo mode didn't kick in as often. The computer probably decided that because of the lower octane rating, it had to use 16-valve mode most of the time to avoid knocking.

"Premium", or RON98, "feels" nice, but you can also "feel" it being burnt away faster. I dunno, maybe it was just my wallet talking - anyway, efficiency wasn't very good with RON98 either.

[cube]

My car "requires" mid grade according to the dealership.

But I've put nothing but regular in since I bought it and it drives just fine.
............

Forget about what the dealership says what is the manufacturer's specification? Unless you wish to forfeit your warranty, I would not go against the manufacturer's specs. Mind you I'm not the type to worry about breaking anything. I have taken countless electronic/ mechanical products apart to "play with" and sometimes I might even put it back together without having extra components leftover. But even I wouldn't mess with manufacturer's specs when it comes to cars. There's a reason why they exist.