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Hi, im just wondering what octane gas I should use. In the owners manual is says to use 87, but to my knowledge isn't 91 always better. 91 octane is supposed to be for, correct me if im wrong higher compression motors. So does the V6 mazda 6S motor need 91 or is it just a waste?

I also know if the motor is supposed to use 91 and you use 87 it will throw on the "check engine" light, because the emissions sensor will read incorrectly if 87 is used. I'm currently using 91, but I really dont want to waste money if its not going to really matter.

Thanks!!!!!!!!
 

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87. Only 87. Never 91. Premium is most definently not "always better". You're doing more than just wasting money -- Burning a higher grade fuel than your car is tuned to run actually hurts the engine (actually the exhaust system), decreases your fuel economy, and costs you power.
 

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As stated above use 87 ONLY. A friend of mine who is a service tech for GM told me that you should always use what the owner's manual recommends when it comes to what the octane is. It can hurt your engine if you put any other in it.
 

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trust me 93 means you pay more per tank of gas. If you aren't after marketly tuned, Spraying n2o, Or Speed badged from the factory you are paying for nothing but heartache. Damn shell and their (watered down) V-power is better adds!
 

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I use 89 currently and I don't care what everyone else says either way...I wont use 91 92 or 93 because - agree - it is over the top and not neccessary...Since I have the MTX trans I find that sometimes "under load" in the low rpm range the shifting is "more smooth" when using the 89 as apposed to 87...It's for me like using the "monster cable" on my vidieo equipment...
 

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...Since I have the MTX trans I find that sometimes "under load" in the low rpm range the shifting is "more smooth" when using the 89 as apposed to 87...
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:huh:

How does 89 octane gasoline give you smoother shifts?

It's for me like using the "monster cable" on my vidieo equipment...
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Once again... :huh:

In this case, MT-90 for smoother shifts is equivalent to your example, NOT 89 octane! :slap:

Have fun wasting your $$$.
 

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Since I have the MTX trans I find that sometimes "under load" in the low rpm range the shifting is "more smooth" when using the 89 as apposed to 87...It's for me like using the "monster cable" on my vidieo equipment...
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Like your 89 octance usage, monster cables or cables of equal quality actually make a difference when used with the appropriate system. A $50 DVD player hooked to a regular CRT TV doesn't need them, but you bet you'll notice a difference with HD signals :)
 

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There has been a lot of discussion about some sort of odd knocking sound when at low rpm's ... just as you step on the pedel to accelerate. You can compare how your car behaves as you change from 87 to 89 octaine and back again. To be fair - it really takes about 3 tank fills to fully "switch" over. I feel that the 89 octaine limits this "odd" behavior at low rpm's. Also if you are in 5th gear going uphill at about 60 mpr...floor your car in5th gear and see what happens...it has been my experience that 87 octaine will give just a slight "hesitation" while at (wot) (wide open throttle) going uphill (under load) while using 89 octaine provides a constant smooth acceleration. Feel free to give this a try...I don't see this as a waste of money. Once again - I agree - there is simply no need for 91/92/93/94 octaine. Perhaps I am wrong...it's sort of like a reluctance to actually buy no name brand Tylenol. Is CVS Brand Acetominofin "really" exacty the same as "Tylenol"??? Some say YES it's just that the no name is much cheaper because they were not responsible for expensive Research and Development (R&D). Others are steadfast and say NO the manufacturing process is not the same and what you get in the off brand may or may not really be "Tylenol". In the end you pay more for what you "believe" you get!!! Why else would someone pay good $$$ for bottled water and forgo the tap which is free??? Go ahead and try my hands on test...maybe just maybe...someone will actually agree...
 

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FWIW,

Octane rating is gas's ability to resist detonation. The higher the octane, the harder it is to detonate. That's why you need higher octane in high performance (high compression) motors and turbo (turbo creates high compression) motors. As compression increases, the gas needs to be able to resist combustion until the spark hits. If it doesn't, the motor will knock or ping.

A higher grade of gas shouldn't actually hurt anything. It'll burn clean. It's just that you don't need that quality in a lower compression motor.

A mechanic I know used to race legacy series stock cars (3/4 scale w/ 4 cylinders). He actually ran regular 87 gas in his race car because the motor didn't require any more.
 

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Any knocking can actually be caused by pinging (resistance to detonation not high enough in the fuel.) But this should only happen in very high temperatures or high altitudes and certainly has nothing to do with transmission smoothness. So if you noobs find your car is pinging (ask us first), you may want to switch to 89 for the summer months.
 

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I use to put in a higher grade just to be nice to my motor anyway. But with the gas rising up again. Its back to plain old 87. :(
 

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I run 93 bitches!!!

J/k why would you pay for something you don't need?
 
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