well lately it seems i haven't been getting quite the same fuel economy on my DIC... i havent been driving THAT crazy...but usually im hangin around 25-27 and now im at 23, and cant seem to bring it up even after a decent highway ride. think i should change my fuel filter? never done it..and where would i get one?

also, i wanted to know what you guys thought about using higher octane fuels, specifically in the GT with no boost. i know high octane is used to prevent knock from happening, but is there anything else 'premium' about this fuel? and is there ANY knock on a GT? i have a choice of 87, 89, 93, and 94 at my local station..
thanks

I wish there was a 91 level . I've heard rumors that the higher the octane level the more amount of time the fuel lasts. But I don't know if thats true.

It's not hard to change the fuel filter. This will help:

http://www.pfyc.com/supportfiles/gasfilter/

You can get one at a local parts store. Personally, I would stick with OE.

As for fuel, there is knock. This is the tricky part... if you don't have mods, then I wouldn't worry about it too much. Think it would be a waste of your money. However, if you do have mods, then premium is a must.

I don't think you'll see much difference in MPG by changing the fuel filter not to say it isn't a bad idea. I live in a hilly area south of Syracuse NY and I typically see what you're getting and I just replaced all the typical items you replace at 60k(plugs, fuel, air, etc) Even after installing the U-bend delete I didn't see a huge change in MPG either.
I went up to the Adirondacks over the weekend and was getting 30 mpg on the thruway at ~75mph.

Outside temps play a role with mpg. The hotter it is the less oxygen there is so the harder the motor has to work.

As for higher octane. Any unboosted car will see no gain in mpg by upping the octane level. Unless you have lots of carbon build up and your engine is experiencing KR.

i'd be more interested in performance...
would there be a difference between 91 and 94 with a standard intense pcm?

I believe the only thing higher octane does is help fight KR (as Herc said).

So, if you currently have KR then a higher octane would free up some HP and give more power. If you don't have any KR, switching to higher octane would be a waste. At least this is what I've always read.

Zuul, try running a can of injector cleaner in your fuel tank. This might help.
I run a can in at about every oil change.

Higher octane fuel will get you better MPG.

Only if you are currently experiencing Knock. Otherwise your wasting money.

Hello,

I used to run premium in my little Blazer, until I read an article that it may actually be detrimental to an engine that doesn't require it. I noticed a gain of a couple MPG on the freeway after switching from "Premium" to "Plus". I'm afraid to drop to regular.

Later now,
Clint

It gives me about 3 mpg in my bike.

That's cause your bike is a high compression ratio'd motor. My Vstar also recommends 91 RON not sure how that fiqueres into the whole R+M/2 method.

so is there anything premium about premium besides the octane rating?

The cost???

Some of the bigger names like Mobil, Exxon, Shell add in some detergents to make it more marketable to those who don't need it. But otherwise no there isn't. And actually some detergents will foul plugs faster then need be. The best thing to do is use the octane the factory recommends and to use a total fuel system cleaner with each oil change. Much cheaper and better in the long run.

Here is something I learned while in a mechanics class: On modern engines with sophisticated engine management systems, the engine
can operate efficiently on fuels of a wider range of octane rating, but there
remains an optimum octane for the engine under specific driving conditions.
Older cars without such systems are more restricted in their choice of fuel,
as the engine can not automatically adjust to accommodate lower octane fuel.
Because knock is so destructive, owners of older cars must use fuel that will
not knock under the most demanding conditions they encounter, and must
continue to use that fuel, even if they only occasionally require the octane.

If you are already using the proper octane fuel, you will not obtain more
power from higher octane fuels. The engine will be already operating at
optimum settings, and a higher octane should have no effect on the management
system. Your driveability and fuel economy will remain the same. The higher
octane fuel costs more, so you are just throwing money away. If you are
already using a fuel with an octane rating slightly below the optimum, then
using a higher octane fuel will cause the engine management system to move to
the optimum settings, possibly resulting in both increased power and improved
fuel economy. You may be able to change octanes between seasons ( reduce
octane in winter ) to obtain the most cost-effective fuel without loss of
driveability.

No, the best thing to do is scan for KR. If you're getting no KR with 87, then going to 89 is a waste. If you have KR with 87, and you go to 89 and get no KR, then going to 91+ is a waste. You can't go with what the factory recommends unless your car is the way it came from the factory. Modded cars need to be scanned to tell what you need. My .02

Hercman,

I did a search and found out that the difference between RON and the (R+M)/2 is 1.0454 to 1 (RON to R+M/2). So your bike requires 91 * 0.9565 = 87.04 R+M/2 gasoline. So regular 87 should be just fine for your bike. Hope this helps. Here is the link that I got the information from:

http://www.asmaracing.com/TracksideSupport.html

Thanks Caesar.

As for 99GT2dr,

Not everyone has access to scan for KR and not everyone has a modded car. I was giving general advice that applies to most vehicles.

i've got a scanner coming in about a week or so hopefully.... im eager to check out the knock retard!!!!!!!!