Thanks everyone. We will use what is supposed to be used. The owner's manual gets delivered this week so we can see exactly what octane is required.

Your manual probably reads that you should use "premium", or some certain AKI (antiknock index, what we used to call octane rating) number, for optimum performance. That means no reduction in fuel economy or power output.

It also probably reads that you can use some mid-grade fuel, or (again) some certain lower AKI, as a minimum. However, you will find less than optimum performance. The reason is that the engine will occasional ping in certain conditions (load, acceleration, temperature, etc.) that will make the computer reduce the spark advance and change the fuel mixture.

This will lower your fuel economy, at the very least (it also lowers power output, and is not good for your combustion sensors, etc.) So think about this: if you save 10 cents per gallon, that's about (at today's prices) 2.5% of the cost of your fuel ($0.10/$4.00) -- you will certainly experience more than that reduction in fuel mileage, so you're actually losing money from that decision.

And absolutely No, you cannot change the timing on your car. Sure, when distributors could be manually "rotated" to change the ignition timing, that could be used to prevent ping (but it retards the spark and reduces economy and power). However, in our newer cars, the timing is controlled by a computer based on the position of the crankshaft (i.e., flywheel), and rotation of the distributor (if even possible) has no effect.

Really, your car will be happier long term with the specified gasoline and will have more power. If you want a car that runs on regular, get a generic Chevy, Ford, Toyota, etc.

The knock sensors will hear any 'pinging' long before your ears can, and when that happens: The mixture gets enriched and the timing retarded, resulting in poor gas mileage and soot coated O2 sensors. Typically, the 'regular' gasoline does not contain any cleaner additives, which help keep the injectors and valve seats clean.

The turbo is more suited to use 87 octane because of the lower compression ratio, BUT, the low pressure turbo comes on at about 1500 rpm and raises the ratio to over 10.5:1.

The normally aspirated engine has a ratio of about 10:1 which requires 'premium' gasoline.

Many have found that if they drive nicely, meaning gentle accelleration and without long hills, the 89 octane works for them. But do not go over 4500 rpm, because the extra heat will cause pinging.

The differencee in price is 10 cents/gallon between each grade. For an 18 gallon tank, that is $1.80 or $3.60 for a tank that will take you close to 500 miles. Less than one cup of Starbucks! Be kind to your car and use the grade that will keep the engine clean and efficient.

Klaus
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Always willing to listen, just not able to take direction.