I was just wondering (Fuel Question)

Check out wikipedia and type octane rating.

It's great... Much better of an answer than I could give you :)

Alot of the small,but high H.P. engines require the mid grade. My SIL has to use it in her BMW and the neighbor needs it for his Nissan. Where do you find 89 cheaper than 87? If it's cheaper, I may switch for my two gas powered vehicles. (TV is diesel)

bob213 wrote:
Alot of the small,but high H.P. engines require the mid grade. My SIL has to use it in her BMW and the neighbor needs it for his Nissan.)

Yup, my daughter's BMW, my SILs BMW, and my BIL Mercedes all require premium gas. My other DD has a Nissan and it is recommended but not required so she uses premium every 3rd or 4th fill up to prevent knocking.

Mjoseph320 wrote:
Yup, my daughter's BMW, my SILs BMW, and my BIL Mercedes all require premium gas. My other DD has a Nissan and it is recommended but not required so she uses premium every 3rd or 4th fill up to prevent knocking.

OK, I have trouble understanding the effectiveness of that choice. Higher octane will only prevent knocking when that is the fuel that is in the combustion chamber. This means that you will only be having an effect, every 3rd or 4th fill up. In between fill ups will be just as prone to knock as if one ran low octane all the time. Even if you are filling up at a half tank or above, means the dilution of the octane boosters will have no real effect. Secondly, the computer will prevent knocking anytime the octane is too low. Any modern engine recognizes the knock, and detunes the engine, so it won't knock. Detuning reduces available power. So what that means is that every 3rd or 4th fill up, they have increased available power. You probably don't notice it unless you run wide open throttle, where the air pressure in the cylinder would be high enough to cause knock. Otherwise, you will never know the difference.

The mid-grade is about 99% marketing. If there is a car out there that the manufacturer says that 89 octane should be used in, I don't know of it.

The cars, that I know about, have one of the following recommendations:

1. Regular (87 octane)

2. Premium (usually 91 or 92 octane)

3. A few OK regular but say that max power comes with premium. These are cars with sophisticated knock sensors and computer programming.


If your manual says that regular gas is recommended/required, that's all you need-----------------unless your car's tune has deteriorated to the point that it is pinging. Than 89 octane might be a short-term solution, but your engine needs some attention.

My 1999 Deville Concours, Says right under the fuel gauge to use only Premium. 185,000 miles
My 82 Pace Arrow 454 4 bbl runs better on premium more pep no pinging.48,000 miles
My 1964 deville convert uses Premium/non oxygenated 71,000 miles
I run Premium every tank.
Sorry but I think it makes all the difference.:B

spritz_55423 wrote:
My 1999 Deville Concours, Says right under the fuel gauge to use only Premium. 185,000 miles
My 82 Pace Arrow 454 4 bbl runs better on premium more pep no pinging.48,000 miles
My 1964 deville convert uses Premium/non oxygenated 71,000 miles
I run Premium every tank.
Sorry but I think it makes all the difference.:B

My 2003 325HP Northstar STS said premium fuel but I always used 87 and it ran perfectly fine for the last 60K miles.all smoke and mirrors on newer port injected computer controlled engines

The OP's first question is why is Plus grade cheaper than Regular in the Mid-West. Are there any Midwesters out there that know why? Curious minds want to know. Here in the Pacific NW, Plus costs more.
As to octane, more may not be better, but modern engines are pretty adaptable. I have an '08 Chrysler 300 with a V6 and the manual basically says that 87 octane is fine but it will have slightly better performance with 89. I'm a cheap bugger so it only drinks Regular.

87 octane fuel is used at a rate much faster than the mid and premium grades. Sometimes if the price of fuel is rising quickly the prices on the 87 tanks change but the mids and premium may wait until their next fuel delivery.


Doug

coolcity wrote:

spritz_55423 wrote:
My 1999 Deville Concours, Says right under the fuel gauge to use only Premium. 185,000 miles
My 82 Pace Arrow 454 4 bbl runs better on premium more pep no pinging.48,000 miles
My 1964 deville convert uses Premium/non oxygenated 71,000 miles
I run Premium every tank.
Sorry but I think it makes all the difference.:B

My 2003 325HP Northstar STS said premium fuel but I always used 87 and it ran perfectly fine for the last 60K miles.all smoke and mirrors on newer port injected computer controlled engines

Both arguments are erroneous and have absolutely NOTHING to do with octane rating.