So I was wondering if I ran 89 through a tank how many more KM could I get out of a tank of gas? I ran 87 and got around 500KM to the tank of gas on 33" nittor mud grapplers. Just wondering if I will get a noticeable differance? Like if I will get another 100KM to a tank I would definately use 89 opposed to 87 but the higher 89 octane is 10cents more for a litre. Thanks

 

I don't have the numbers anymore since I've been running a performance tune on my Hemi with 93 octane fuel since early '06. But I know the higher the octane I used when stock, the better fuel economy I got.

BUT I can tell you that EVERY Hemi I've seen with one or miltiple blown cylinders, that was not the cause of a broken vavle spring, the owner has admitted to running 87 octane fuel on a regular basis.

Not saying you are gonna blow your engine if you run 87 octane, but I like the 10 cent per gallon "insurance policy" myself.

I know the manual says "87 OK, 89 Recommended", but I personally don't think they should have given the option to run 87 octane at all...

 

you guys may only pay 10 cents more per gallon but we pay 10 cents more per litre which is quite a bit more

 

I know when i first got my Hemi i was running 87 do to it being $1.05 per liter (average) and the 89 runs about 7cents more ( 2 hrs west of you in Toronto ) and i think the engine runs and performs much better and i do notice better fuel milage I am not going to say i get 100 km per tank or anything but i feel it is worth it ..

 

3.7 lt = 1 gallon.

I allways try to run the highest octane at the pump I can find, I have stock tune and my hemi responds to the higher octane flue, as mentioned 87 octane causes problems with long term use, as my gen rule I use mid grade for day to day driving, 92 for highway, towing, in Calgary 92 runs abought 1.18 a lt.

 

Today we had $1.22 per liter octane 89. I do run 89 and I don't think that the difference between 87 and 89 so noticeable, about 1 liter per 100 km.

 

Just switched to 89...Figured it was a good insurance policy to pay the extra cash!

 

I run 93 in mine religiously as do I make the wife do it in her Mini. Hammer is correct that we have seen guys come in here with ruined pistons and all admitted running 87. I wont go as far to say that is the main cause but it sure isnt helping.

 

I agree with everyone else that the Hemi's are built to run 89. Once you start to mod them you are throwing the computers adjustments out of the normal range and they may not be able to compensate enough to keep the engine safe when abused. Engines don't heal either, once damage is started it will continue. It may be a week, it may be 2 years until it shows its ugly head.

Engine tuning is not as simple as it may seam. Especially when your balancing compression ratio, cam timing, spark advance, emissions, etc...

From what I remember the higher the octane the harder it is to burn (resistance to knock and preignition). Your engine will take more energy to burn the mix of a high octane with everything else being the same, so it mean energy output is down slightly. Don't read into this as it must be fractional at best, but it makes sense to me. Maybe over 1000 miles you might be loosing a couple. I'll pay the few extra cents per gallon to avoid blowing ring lands off my pistons.

 

Im confused, here our 89 is the "cheap" gas. 87 costs 0.10$ more here. It sounds like everywhere else it is the exact opposite. I use the 89 but why would 87 be more expensive?