I was talking to a friend today that said that putting premium (92 octane) gas in the hemi truck causes it to misfire because of the higher octane amount. Is this true? should i only put mid grade in it or is premium better?
That's a new one to me, having a 91/92/93 octane pump gas actually cause a misfire in any normal modern vehicle. I haven't seen or heard everything, but I'd like to hear the specifics about how it's supposed to happen. As to the value of the fuel in performance vs. price vs. economy, it's a debate that rages all the time. The claim for higher octane is that it will produce a small power increase because the anti-knock sensor, timing, and other computer controls will allow the engine to yield more power. There's some truth to this in very small quantity. Fuel enconomy "can" improve in some cases, but it's debateable how the price and mileage gained balance out. As an engine gets more extreme in its tune/components or at least the useage gets more extreme, the higher octane probably does yield more useable power. Under real "hotrod" or maybe even towing conditions, the higher octane fuel might be more noticeable in its value vs. performance. Here's a link about fuel octane and even octane boosters that might be interesting.
I was running 89 in my 2009 until I noticed the cylinders knock under load such as going up a hill in cruise, I've now switched back to 93. We have 87, 89 and 93 here. I don't think your friend is correct.
As others have said it might be a waste of money, but I personally dont think it will hurt it any. I rarely ever run 87 in my two Hemi's, It's 89 98% of the time, To me they run better on 89. Sometimes I treat them to a tank of 93 or even add the 93 to the 89.