Use Of Premium Fuel

[JohnYafmen]

In the July 2007 issue of Scientific American, in the 'Fact or Fiction' section, they explain how it's no longer necessary to use premium fuels because of how engines are designed these days. Has anyone tried to use regular gasoline?

thanks.

John

[Grumpa72]

I have been using regular grade from day 1.

This has been discussed on this board as well as the BMW discussion board I visit. The gist of the information is that our cars have a knock sensor that detunes the car if it starts "hearing" knock from the engine. Knocking indicates that you are demanding more from your car than your fuel can deliver. I would suggest that most of us never need the 200+ horsepower that are under the hood of our vehicles.

I am one of those who believe that horsepower ratings by the manufacturers are merely a marketing and advertising tool.

Ok, off my soapbox.

Gary

'05 330

[wwest]

I have been using regular grade from day 1.

This has been discussed on this board as well as the BMW discussion board I visit. The gist of the information is that our cars have a knock sensor that detunes the car if it starts "hearing" knock from the engine. Knocking indicates that you are demanding more from your car than your fuel can deliver. I would suggest that most of us never need the 200+ horsepower that are under the hood of our vehicles.

I am one of those who believe that horsepower ratings by the manufacturers are merely a marketing and advertising tool.

Ok, off my soapbox.

Gary

'05 330

Actually there are two distinct causes for a modern day engine knocking. Too lean mixture, octane too low, or lugging the engine.

Most modern day cars will simply enrich the mixture to correct for the first two and some will downshift the transmission, assuming a lower gear is available, for the latter.

[Grumpa72]

Actually there are two distinct causes for a modern day engine knocking. Too lean mixture, octane too low, or lugging the engine.

Most modern day cars will simply enrich the mixture to correct for the first two and some will downshift the transmission, assuming a lower gear is available, for the latter.

I agree with your statements, at least from what little I know of modern FI systems. I was specifically addressing knocking from an octane point of view. The FI systems today will run on regular grade, some better than others. If you have a 500 hp, high performance beast, it may not run well at all. However, in most family style vehicles, I would bet that most of them run just fine on regular grade gas.

As an example, my wife's '05 330 states that regular grade fuel is just fine as long as you don't mind suffering a small loss of horsepower. Like she would even know the difference? ;0 I drive a 2007 BMW 328xi and the owner's manual states that regular fuel of 87 octane is just fine but premium will give the most power. Sounds familiar doesn't it? Oth, the BMW 335i with twin turbos states that premium fuel is the minimum fuel requirement. There may be some instances where the 335 just won't run well with regular gas. Of course, what do you do with your vehicle if you are in Timbuktu and all that is available is regular?

Gary

[wwest]

Actually there are two distinct causes for a modern day engine knocking. Too lean mixture, octane too low, or lugging the engine.

Most modern day cars will simply enrich the mixture to correct for the first two and some will downshift the transmission, assuming a lower gear is available, for the latter.

I agree with your statements, at least from what little I know of modern FI systems. I was specifically addressing knocking from an octane point of view. The FI systems today will run on regular grade, some better than others. If you have a 500 hp, high performance beast, it may not run well at all. However, in most family style vehicles, I would bet that most of them run just fine on regular grade gas.

As an example, my wife's '05 330 states that regular grade fuel is just fine as long as you don't mind suffering a small loss of horsepower. Like she would even know the difference? ;0 I drive a 2007 BMW 328xi and the owner's manual states that regular fuel of 87 octane is just fine but premium will give the most power. Sounds familiar doesn't it? Oth, the BMW 335i with twin turbos states that premium fuel is the minimum fuel requirement. There may be some instances where the 335 just won't run well with regular gas. Of course, what do you do with your vehicle if you are in Timbuktu and all that is available is regular?

Gary

"if you are in Timbuktu...."

When we picked up our '01 Porsche 996/911 (300HP/high performance[??]) at the factory I was told that in our travels throughout europe we would not always be able to buy premium fuel, and that would be fine, but we should not refuel with leaded as that would require a new catalyst ($1000) before shipping stateside.

[tjmc11]

Bottome line - It does not make a difference that is noticable. If you are driving a Ferrari which is a highly tuned vehicle and engine, or a hemi, it can make a bit of difference. In vehicles like ours, it will not matter and you will gain no noticable advantage either way other then carbon deposits / exhaust differential etc. which are miniscule either way.