I just got a 2003 pathfinder and it says use gasolne with an octane rating of at least 91. What happens/bad side effects will happen if you do not use premium gas? will engine knock happen for sure?

*i really thought i posted this in the off topic section. My bad.*

If the engine is tuned for premium, it is tuned for a slow burning fuel...and the timing is set to take advantage of the time from the ignition spark to the push on the piston, etc...

If you use a lower octane fuel, the burn time is faster (Flame propagation, etc...), and the ignited fuel will try to push the piston sooner than if you had a slower burn...

so - you might try to push the piston while it is still coming towards the spark, rather than just as it starts away again...

So - Its like you are pushing a kid on a swing...

...and give your shove while the kid is coming towards you, and you knock the kid off the swing.

That's "Knock"

If you just jolt the kid a bit early, but he hangs on, that's "Ping".



So - you should have a knock sensor, which should adjust the timing to keep the kid from getting too banged up...

But, now you are just pushing later, and softer, in fail soft mode so to speak.

The kid wants to go higher and further...but you are too retarded (Timing Joke...) relative to your timing to do it.

TJ, if i can just say, thats gotta be one of the best explanations i've read in a long time

The "kid on a swing" explanation surfaces again.

So how would you explain throwing a rod with the same example? Taking a kid and shovin him through the cylindrical slide in the playpen?

haha thanks tj, good explanation. So pretty much. DONT DO IT!? or if i do use reg gas the ecu will reset for the change and i will loose power.