MGB Gas Octane for MGB's

[Steve_S]

We get no MTBE fuel here in CA. The last I saw of it was early last year at Chevron.

 

[swift6]

MTBE shouldn't be anywhere anymore. They figured that it was bad for the environment. The 10% Ethanol we now have is not MTBE. In the broad strokes, it is 10% corn squeezin's while E85 is 85% of the same stuff. Old rubber bits in the fuel lines love to fall to pieces when presented with any of the ethanol. Fuel vaporization also happens at lower temps. So you are more apt to see vapor locks with this stuff. Add together high altitude, high summer heat and 10% ethanol fuel and you have a whole new range of tuning issues that we get to deal with.

My basic point with the first post was that we don't get the choice of searching out stations that don't mix their gasoline's with 10% ethanol. They all do it here. On the plus side I guess is that because of the politics surrounding it, all but three counties in Colorado no longer have an emissions test program. Although the scuttlebutt at the state level is that we might be getting a new statewide system that will be NOx based like California instead of our old CO based system.

 

[RickB]

I've used the 92 from Costco gas the past couple fill ups.
One thing I noticed is a bit of increased mpg. That's kind of nice, it does feel a little peppier also.

I probably break even at just 20 cents a gallon more than the 87 considering a little better mpg.

The cost is just 6.6% higher so that would break even if I increased from 23mpg to 24.5mpg - and hopefully my engine has other benefits from the 92. One thing for sure, the 92 gas can't hurt my car.

 

[Mac_Townsend]

I use 87, in a 9.x CR engine. No problem.

 

[PAUL161]

I was just in Mississippi and it seems like all the gas stations are selling 10% Ethanol gas. There is a slight loss power in my truck using that stuff, which means a loss in MPG.

 

[tony barnhill]

And just something else to add fuel to the fire (hehehe):

In my big Dodge truck, BP/Amoco gets the best gas mileage, Chevron/Texaco 2nd best, & Exxon a far 3rd! All the same octane rating.

 

[jlaird]

"fuel to the fire" sigh

 

[MGBGT_noob]

That's right. Look at the passage that says "93-octane Research". If you look at an American gas pump, you'll see that the label says "XX Octane (R+M)/2 method".

The R stands for "Research", a method of determining the knock-resistance of a give fuel formula, under "ideal" conditions.

The M stands for "Motor", a method that tries to measure performance under "real world" conditions.

The Motor octane rating of a given fuel almost always comes out lower than the Research rating. Therefore the (R+M)/2 number will fall halfway between the Motor and Research values. It all depends on the composition of the fuel. Some fuels have values closer together than others.

In Europe, they use the Research rating exclusively. Thus the US rating will usually come out lower for the same fuel. "93-octane Research" might equal 89 or 90 octane, (R+M)/2.

Further reading I found this section about HC & LC engines:

<span style="font-style: italic">"When fitted with H.C. engine (compression ratio 8.8:1)

The octane number of a mtor fuel is an indication given by the fuel technicians of its knock efficiency. High-octane fuels have been produced to improve the efficiency of engines by allowing them to operate on high compression ratio, resulting in better fuel economy and greater power. Owing to the high compression ratio of the 'MGB' engines, fuels with an octane rating below 98 are not suitable; should it be necessary to use a fuel with a lower octane number, the car must be used very carefully until the correct fuel can be obtained.

It is necessary to use Super grade fuels in the 100-octane range unless Premium fuels of minimum 98-octane are available.

When fitted with L.C. engines (compression ratio 8.0:1)

Premium fuels of minimum 93-octane Research up to 97-octane are required, with preference to 93/97.

Super fuels in the 100-octane range can be used if preferred."</span>

Wonder what their 100-octane fuel relates to today? Same with their 98-octane?