Hi there,

I read some where on the Internet that I am supposed fill up with 89 instead of 87. Is it really necessary??? However, somebody told me that 89 is a rip off and was told to fill up with either 87 or 91.

FYI, mine is SXT 3.5L AWD.

 

I'd go ahead with using 89 octane. Although modern engines have technology that are supposed to prevent spark knocks and pinging from happening, it doesn't always work. By using 89, it doesn't hold back on the output that the engine produces as it would have to with 87. The only reason I know of that someone would say to go with either 87 or 91 is the concern that at some fueling station they will have 10% Ethanol as their mid-grade offering that is at the same price as regular (sometimes even cheaper depending on the price of Ethanol to that of gasoline). The route of this belief system is because this was how it started out as farm co-op places like MFA Oil, Gateway FS started this, followed by chains such as Casey's that almost exclusively do this, and even some major brand stations will do this. Now days depending on what state you are in, many stations have 10% Ethanol in all grades.

The reason for dislike and concern is Ethanol has less energy in it which is why E85 isn't a practical solution; however, in the 10% level the difference is so small it is hardly measurable outside of a margin of error. I use 10% Ethanol all the time and get excellent results (not that I have much of a choice since there is only one station around that has 100% gas in the 87 octane offering and my engine runs better on 89.

I prefer to stick with what is recommended. My theory is if you want it to last, use everything they recommend because they recommend it for a reason.