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i run 93 in my turismo and my daytona as it makes it run a heck of a lot better than 89
 

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I remember back in 86 I was delivering pizza with my 85 Shelby Charger (AH!, Memories), anyway. I got much better fuel economy running premium over the lesser grades. In fact it made up the difference in price to run the premium.
I also know that my 87 GLHS with a heap more power is doing even better than the 85 ever did for fuel economy.

Law
 

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i only run premium or if i am broke i will run 89 but i can tell a differnce in fuel mileage, my sundance gets 24mpg with premium and with 87(long story) it will only get 17 to 18mpg, my mini doesnt care what it has lol dont know why but it gets 22 with all fuel grades. but i still run 89 or better, the only thing i run 87 in is my 90 2.5 dakota just becuse it get better with the cheap it will get 21mpg with 87 and the other grades do the same so not a big deal,
 

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It is worth testing your fuel economy at each level, but with the 4 and 6 cylinder cars I have had, I have found premium fuel made a huge difference with regard to fuel economy, while the V8s showed no real difference. If you're just cruising around and not getting on it all of the time, the lower octane is probably fine, but run a tank or two of each and record the results to determine if it is worth spending a little more per tank at the pump. For me, it has paid off.
 

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It is worth testing your fuel economy at each level, but with the 4 and 6 cylinder cars I have had, I have found premium fuel made a huge difference with regard to fuel economy, while the V8s showed no real difference. If you're just cruising around and not getting on it all of the time, the lower octane is probably fine, but run a tank or two of each and record the results to determine if it is worth spending a little more per tank at the pump. For me, it has paid off.
lol i only tested the fuel at differnt levels in my truck becuse i was driving 5 hours one way and i had nothing else to do! LOL :p and with my van i was curious becuse i ran 89 and it was good so i tryed 93 and it didnt change? :( my sundance my mom put a full tank of 87 in it! well it lasted 2 days of driving.. and was spark knocking alot while driving.:bang head
 

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So still kinda up in the air, again like I said not much racing around town, just cruising and what not, and mileage still sux!
But worried about knocking and blowing it up if I run less than 92-93!!!
You aren't likely to do either, really. Depending upon where you drive, you will have higher or lower octane for premium anyway, so if you were to drive across the country, you may come to a point where premium is 90 octane. If you're driving the car hard, the higher octane will help performance, but if you're just cruising, you may find the lower to work.

Either way, for my driving, I found my two Daytonas both get better fuel economy with 93 vs 87 or 89.
 

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Discussion Starter · #13 ·
Well I can say wont be driving cross country anytime soon!

But it is kind of nice to hear that something less premium won't be
Terribly dangerous to my td!!

Could it hurt to mix like half tank 92-93 and let's say regular or mid grade??
 

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Discussion Starter · #14 ·
Let me ask this ?,
Is there a chance that the mods done to this car have seriously effected gas mileage, as I don't know how it was previously!! And I know it wasn't or hasn't been tuned only had a moparman dcal done to it!!!
 

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I have never tried mixing fuel grades to see if it would be worth the hassle, but I have known people who have mixed them for one reason or another. As for mods, sure they can have impact. I actually saw a 6 mpg improvement after extensive mods on my TII Daytona. It would depend upon what was done and if it was done correctly.
 

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Again, back with my 85 and delivering pizzas, I did mix 1/2 and 1/2 between 87 and 92 Octane with the equivalent power and slightly better mileage than either grade alone. That might just have been in my teen-age brain tho. I only did it for 3 tanks because I thought it was a pain to do and I was rolling in pizza tips...LOL

Best places to start looking for improved fuel efficiency is
1) Clean air filter
2) Cleaned and properly gapped plugs (hotter too maybe?)
3) check that timing is bang-on

I may just be talking through my hat though. I'm sure there are lots of other guys with more/better info that would be willing to help you.
mpgmike is a good source of information and he has lots of experience working on the Xprize stuff.

Good luck
Law
 

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I thought the octane rating was simply a resistance ratiing. Meaning it resists detonation.
Depending the needs of your engine ie: compression ratio, determines the octane rating used.

It has been tested many times over the years, mostly in the racing crowd, using higher octane gas when not needed actually produces less power. (because of the higher resistance).
I don't know about increasing or decreasing mileage, that was not the purpose of all the tests I have seen, so I won't get into that dabate.

Pump gas, as mentioned, is not reliable on the ratings. Probably why there are different results for some of you guys.
 
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