I currently have a 2008 Mitsubishi Endeavor SE which I bought 4 months ago. I haven't had a single problem with it until just the other day when I filled it up. Granted, I used 89 octane instead of 91 but now I am hearing a sloshing sound coming from the fuel tank which I have never heard until now. Any ideas?

 

If your owners manual calls for 87, don't use anything else.

There is nothing wrong.

 

I used 89 and the owners manual says 91.
I'm just a little freaked out because I have not heard the fuel sloshing around before.

 

Use 91, don't be a cheap ***. There's a reason for it, google it.

 

If the owners manual calls for 87 then yes its a waste of money to buy higher octane... If it calls for 91 yu shood use 91 oct etc... I have two 3000 gt vr4s that call for 91 onlee but i have used 87 lots of times and experienced no real known issues by doing so what so ever but try to use what the manual calls for