Quick octane lesson: higher octane has less energy in it. It is used to add horsepower by adding timing and increasing cylinder pressure.

Using premium in an engine with a PCM that can't really adjust for it, like ours, can/will reduce mileage. Age can increase the octane need through hot spots that develop from carbon or sharp edges that form... but I say you give regular a chance. Do a few tankfulls at least.

Well, that explains why i always seem to get less mileage on higher octanes...

I have a 1993 Bonneville SSE with 195,000 miles...... always use regular gas, and always get 20 mpg

My 20 mpg is a combo of highway/city, A/C ALWAYS on, and sometimes watching the boost gage jump, so I guess I'm normal. I'm taking it on a trip to Vegas Friday night, so we'll see how she does with complete highway driving.

I agree with this comment, and so do others, including professional race car drivers - using high octane gas in a normally aspirated engine designed for regular unleaded gas is a waste of money.

I get up to about 26MPG, mixed now that it'* warm. But, I just changed my O2 recently, switched to full synth oil, and did a tune up. Also, I almost never use the AC. I prefer the feel of the windows down and the music up.

With my 94 SSEI I get an average of aobut 23-25 MPG out of her. Thats alot more city than highway as well.

Erik

23-25 city is exceptional. The states that require the10% ethanol blended fuels, like ours caused people to get 2-3 mpg less. My friend regularly gets 27mpg in his intrepid. He took a trip to PA, filled up there and got 31 on the way home. Just shows you what different fuel blends can do to mileage.
Can't get close to 18 around town with ethanol.

wow! how do u guys get the 33 on the freeway i cant break 27. that driving to detroit at 75-80 for 2 hours. in the city i avg 19 with a medium foot.