Modern computer question / fuel economy

I realize this is off topic (as in not t-bird related) but thought I would ask anyway. I know that historical folks have said that it isn't worthwhile to put higher grade gas in a car that doesn't require it. I'm curious as to whether that still holds true with the newest cars and computers. I've got an '05 Focus and while I may go ahead and do it anyway just out of curiousity, I was wondering if the car would adjust to running premium... mostly from the perspective of improved fuel economy.

Any insights?

There is nothing to adjust. Octane is a measurement of the ease of which a fuel will combust. Higher octane fuel is needed in vehicles that run higher combustion chamber pressures to ensure a proper flame front is created when the mixture is ignighted. This is done through constructing longer hydrocarbon chains that effectively take longer to burn. This is the key component that makes high octane gasoline, high octane.

In a vehicle that doesn't achieve higher combustion chamber pressures, it is possible that higher octane fuel will not be fully combusted by the time the exhaust stroke completes. Thus at best, an engine designed for 87 octane running 92 will show no performance change what so oever. At worst it will have incomplete combustion increasing hydrocarbon emissions, reducing fuel economy, and leaving more than normal carbon deposits.

Thus the goal that most people set is to run the lowest octane fuel you can that doesn't cause pre-ignition when operating across it's range of performance. Accordingly, whatever the owners manual says, should be it.

Ding Ding Ding....We have a winner!!!!!
Mikes right on target, your engine is not designed to run on Premium fuel so you will get NO benefit from useing it. Your car will probably get alittle less gas mileage as well along with higher emissions. Premium fuel burns slower and you need higher compression to raise the charge temp in your cylinders to get complete combustion.

thanks for the info. In terms of 'adjusting' I was thinking in terms of advancing spark...

plev72 said:

thanks for the info. In terms of 'adjusting' I was thinking in terms of advancing spark...

Click to expand...

There is a (mis)conception that better fuels will clean out your engine better too due to better octane, higher burning temps, or better additives. Like running every 5th tanks as premium or so.

Any truth to this?

JStudrawa said:

There is a (mis)conception that better fuels will clean out your engine better too due to better octane, higher burning temps, or better additives. Like running every 5th tanks as premium or so.

Any truth to this?

Click to expand...

Premium and regular gas has the same kinds and amounts of cleaners and detergents in them and thats what cleans the fuel system and such, octane has nothing to do with cleaning. The only way prem gas will make a good difference is IF your engine is setup to run on premium to begin with but you have been running reg instead, then running a tank of premium will make a difference.
The oil co's perpetuate the switching to premium because they make more money from selling the high grade gas to people that do not need it. Cheveron in my mind is the lessor offender in this case because they do say in there TV ads that there cleaner Techrolene(or whatever its called) is what does the cleaning, thats much closer to the truth than what shell is doing with there V gas(or whatever catchy marketing name they've come up with lately).