hi,
what exactly is premium? it is mentioned in the owners manual and it was recommended by the salesperson.. the manual says use 91+ so is premium anything with the octane rating of 91+ ?

im seeing regular, plus, and super (also, ULTRA at sunoco) at the gas stations here in NJ.. any help appreciated

Also, what gas vendor do you guys trust? Exxon? BP? Sunoco? Mobil? (i think Exxon/BP/Mobil is the same company, not sure if its the same gas)

thanks

 

Any major brand of gas is the same as any other as far as the octane rating, i.e. 91 octane is the same for all major brands. DO NOT use anything less than 91!! Some drivers have asked the same questions and tried mixing the mid-stuff (less than 91) with the premium (91 and higher), but it's NOT a good idea to sacrafice the engine for a few pennies. If you can get 93 or 91, don't burn the money on the 93. 91 octane is fine and will keep the engine in top running shape.

 

so what exactly is "premium"? anything over 91+?

 

Yes, 91 and over

 

so does plus and super vary from state to state? or is plus 91 and super 93? sorry i never used premium fuel before, i always filled regular before i got my coupe today

 

I'm glad you made it home. You sound pretty stressed out over some Big Oil marketing labels.

 

im not stressed out.. the price isnt an issue i just want the car to work great.. its worth it

 

Don't look at the names of the different gases, just go with 91 octane or greater.

 

i see.. thanks.. so what kind of difference is there between 91 and 93?

any difference at all? besides the price?

 

Yes, 93 octane burns faster than 91 octane. Gives a little bit more (probably imperceptable to the normal driver) boost but don't waste your money. Just be sure and use 91 octane and nothing lower.

 

alrighty, will use 91 will also ask the dealer what they filled the car with since i got a full tank from them

 

I could be wrong but isnt 93 octane harder to burn then 91? the more octane it has the better it resists detonation especially in high compression engines?

 

The higher the octane the slower the burn [flame propagation speed].......the graph shape of the burn rate from ignition thru the peak BMEP [~~14-17 degrees after TDC] when the rod angularity is at the point to exert maximum torque on crank.

Knock is when the peak pressure builds too high too early before 14-17 degrees and thus tries to drive the rod straight DOWN into the crank and causes bearing damage, instead of turning the crankshaft.................getting the timing just right is an art.....why oem just use later [after 14-17 optimum timing] to build in some safety reserve for regular or just bad premium.

If the plug fires at 22 before TDC and optimum pressure is achieved at say 16 [after] the burn time [flame propagation speed] is said to be --22 + 16= 38 degrees.

38 degrees at idle is obviously 10 times longer [in fraction of seconds] than 38 degrees at 6500 rpm! If intake and exhaust cams have valves open 248+248=496 degrees out of 720 degrees the total time remaining is 224 degrees, but all the power [turning of the crank by an individual cylinder] ramps up, peaks and effectively declines in 40-60 degrees.

Lean [14.7AF cruise] mixture take longer to burn because fewer farther apart fuel molecules, thus timing may be -30 or even -35, so the burn takes [-35 + 16= 51 degrees]........leaner the mixture more time for knock to start or things to go wrong in flame burn.

The ecu guesses [from preprograming] what it thinks timing should be, then relies on knock sensors to zero in on what is optimum plus a little reserve. Optimum changes from cycle to cycle and thus advance is constantly being tweeked for fuels every 5-10 revolutions.........each ecu has different THINK/REACT speeds.

 

Does 93 really burn faster than 91?

I live in NJ and I always just tell them to fill it up Premium/Super (93) because its only a few cents more than 91 is, and I dont mind spending the total extra dollar or so.

 

Exxon Mobil is one company although they still sell under two brands, BP is British Petroleum (formerly Amoco)