That is interesting it used to be 89 for the auto and 91 for the 6speed.That is really interesting John. I use 91 as that is the recommended octane in the owners' manual. I only use pure gas, so my mileage is pretty good. I got 27 mpg to Rapid City & back. Even when I am in town a lot, it only drops down to 22 to 25 mpg.
From The Owners Manual:will it hurt if I run 93 octane in my automatic R/T
Sounds about where I was at pulling 27 mpg on the highway to and from MA to Carlisle. My work commute is a mix of city and highway and I'm getting around 22 mpg on those fill ups using 92 and 93 octane depending if I gas up at home or work.That is really interesting John. I use 91 as that is the recommended octane in the owners' manual. I only use pure gas, so my mileage is pretty good. I got 27 mpg to Rapid City & back. Even when I am in town a lot, it only drops down to 22 to 25 mpg.
Less chance of knock on real hot days, that is about it.
This is my 2 cents also. Depending where you live and what type of driving you have to do....I could well see how on a 97 degree day stuck in bumper to bumper traffic running 87 in the auto might start recording knock that you would never hear but would start cutting back the fuel and timing. That and having no confidence in the true octane would be reason enough for me to use the 91 if I had an auto transmission. Another thing to consider is the past post I seem to remember where people running higher octane at the track where saying they consistantly had better times. Of course...none of the above matters if getting the very best horse power you can doesn't mean has much has saving the few cents per gallon at the pump has the car WILL run just fine without hurting anything under the worst conditions with the recommended octane if you are not worried about lossing some horsepower.When I had an R/T I generally ran 93 fuel but also usually ran a diablo 91 tune. I don't have much confidence that most pump gas achieves the octane rating on the pump, so I figure to be on the safe side I usually go a bit higher than required.
If I had the auto I would probably run 89 until the temperatures got into the 90s.I've used the recommended 89 octane for 5 years and my car runs like a top. I've noticed about a 1.5 mpg improvement around town since I put the new exhaust on at least according to the evic.
John,I've filled my tank with 89 up until a few weeks ago. For the last three fill-ups I've used 91 (highest available in San Diego). What I have noticed is that my MPG average dropped from 17.5 to 14. I'm not completely sure the higher octane resulted in the MPG drop, in fact it doesn't make sense to me. But for my next fill up I'm switching back to 89 just to see what happens.