MINI2 - MINI Forum - View Single Post - High Octane Fuel

quentinberg007 · Sep 2nd, 2005, 04:02 PM

Quote: Originally Posted by Vizilo

I have just purchased a MCS Converible as a "sister" to my Saab 9 3 Turbo. I am embarrased to say that I generally use regular gas even though super is recommended for the Saab. I do not notice a difference in performance or fuel economy.

I don't know much about cars. Would using regular gas in the Mini be better or worse than using it for a turbo engine?

You do make a good point. You spend CDN$40K on a car. You shouldn't worry about spending another $4 to $5 per tank of gas if you can save on potential repairs. I'll try to do better with the Mini

Seriously, you have supercharged cars (the turbocharged saab is technically supercharged). You need to use the fuel that the owners manual says. My Impreza is naturally aspirated with a compression ratio of 10.1:1. This can easily handle 87 octane gasoline (as per the owners manual). My g/f's MCS is supercharged. The final compression ratio of the air fuel mixture in the cylinder at top dead center is much higher than my 10.1:1 in my RS, due to the supercharger. That is why is makes the same power (165 hp) out of a 1.6L as compared to my 2.5L in my Subaru. Now, if you put 87 octane in the MCS, the air-fuel mixture would auto ignite at a compression ratio that is well below the top dead center compression ratio. i.e. The piston is still sweeping upward and the fuel auto-ignites before the spark plug sends the spark to the mixture. So, you get early detonation of the fuel when the piston is still much earlier in the upswing motion than it was designed to be. You have the inertial forces of the piston going upward and the explosion force of the fuel and air forcing downward. That is bad times, indeed. Seriously, if you want to destroy your engine, keep putting 87 in it. I hope, for you 9-3's sake, that it has a low compression engine with low boost.

~~Quentin

Sep 2nd, 2005, 04:02 PM	#6
quentinberg007 MINI2 Regular Join Date: Nov 2004 Location: Eleanor, WV Local Time: 11:43 AM Posts: 62 Offline	Quote: Originally Posted by Vizilo I have just purchased a MCS Converible as a "sister" to my Saab 9 3 Turbo. I am embarrased to say that I generally use regular gas even though super is recommended for the Saab. I do not notice a difference in performance or fuel economy. I don't know much about cars. Would using regular gas in the Mini be better or worse than using it for a turbo engine? You do make a good point. You spend CDN$40K on a car. You shouldn't worry about spending another $4 to $5 per tank of gas if you can save on potential repairs. I'll try to do better with the Mini Seriously, you have supercharged cars (the turbocharged saab is technically supercharged). You need to use the fuel that the owners manual says. My Impreza is naturally aspirated with a compression ratio of 10.1:1. This can easily handle 87 octane gasoline (as per the owners manual). My g/f's MCS is supercharged. The final compression ratio of the air fuel mixture in the cylinder at top dead center is much higher than my 10.1:1 in my RS, due to the supercharger. That is why is makes the same power (165 hp) out of a 1.6L as compared to my 2.5L in my Subaru. Now, if you put 87 octane in the MCS, the air-fuel mixture would auto ignite at a compression ratio that is well below the top dead center compression ratio. i.e. The piston is still sweeping upward and the fuel auto-ignites before the spark plug sends the spark to the mixture. So, you get early detonation of the fuel when the piston is still much earlier in the upswing motion than it was designed to be. You have the inertial forces of the piston going upward and the explosion force of the fuel and air forcing downward. That is bad times, indeed. Seriously, if you want to destroy your engine, keep putting 87 in it. I hope, for you 9-3's sake, that it has a low compression engine with low boost. ~~Quentin