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I know Eric has gone over this in a video before on octane but I am still a little bit confused. I am getting a different car soon (1999 Mazda 626) with a 2.5L V6 that says premium gasoline. My question is that can I use the mid-grade level and still be fine or is it based on the vehicle? I am not sure where the difference would be between the mid grade and premium. It does have a compression of 9.5:1.
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there is not much i know about these cars but i know the Buick Regal GS and Pontiac Grand Prix GTP have a supercharged engine with a compression ratio of 8:1 or so but beacuse they are supercharged this ups the combustion pressure and it is also recommended too run premiom gasoline in them because of this…
the type of fuel your car requires depends on compression and forced induction and ignition timing and several other factors, but from my experiences you run the car on what Octane it is rated for… maybe someone will say you can get away with running mid grade rather than premium but i would personally recommended staying with the Octane your manufacturer recommends it is possible the engine in your car has a more advanced ignition and running a lower octane will result in that ignition system combusting that fuel much too early resulting in ping or spark knock… lots of factors when it comes too what octane you should run.
From what I could gather the 2.5 Mazda engine uses 9.5 to 1 compression. Using lower octane fuel wont really “hurt” it, but according to the Mazda forums the car will suffer decresed fuel economy. Makes sense really, when lower octane fuel is used the engine will start to ping and the computer will retard timing to compensate. With the retarded timing the enigne is much less fuel efficient and mpg will drop.
This is from the Mazda forums.
Your car uses several sensors (o2, Throttle position, air temp, atmospheric pressure) to determine where to set the ignition advance, base timing and fuel curve. It will re-adjust itself depending on the fuel you use all by itself. The 2.5 will do just fine on 87 octane, and minor gains can be acheived by running higher octane fuel, as the engine can detect pinging and set timing higher for 93 and lower for 87. I run 89 octane during the summer and 87 during the winter (you can get away with this because the ambient incoming air is cooler, making predetonation (pinging) less possible)
any computer controlled car with a distributorless ignition system and an intake air temp sensor can benefit from premium, if the manufacturer allows the computer to adjust for these changes (Thanks, Mazda!) Another reason why the Ebay “intake temp sensor” resistor mod is unnessesary on our cars.Just use premium, It really isn’t that much more to fill up than mid grade/regular (my truck costs $5.00 more per tank) plus then you can avoid the ethanol :angry: in the lower grades of gas. banana:
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