Do I have to run Premium

[wickedz]

I know turbo your suppose to run Premium, but do you really have to? I have a long trip from FL to Michigan and back to FL again, and wanna do it as cheap as possible . If I have to run 93, then I will.

 

[joe sobo]

nikikuh bovice, i just read some of the comments from people that bought it, and i just wanted to say that it is hilarious rofl

 

[LiquidX]

ok, i totally agree with what you are saying. but shockracer posted above that in his area, the highest is 91 octane...............so what?, he must tow his car to the nearest place that has 93, even if the next place is 300 miles away? and i am quite sure that the area that shockracer is from has a mitsubishi dealer that sold 95-99 turbo cars their new............................unless they didn't care that the area they were selling these cars' didn't have sufficent octane fuel

I agree with you as well. I personally believe the octane rating is half for engine health for the more extreme conditions as well as a liability. Not everyone has the same octane ratings so they will use the highest they can get. To someone it'll be 98 and another will be 86. They are both "premium" in their respected areas so whos to say what premium is without the manufacture stating an octane rating.

Higher the octane the less chance for knock when boosting. If you don't boost I would say you can use "low" grade fuel but it may run shitty because the turbo is still blowing air into the motor. If you don't plan on boosting, use a lower grade for the trip if all you are doing is cruising. If it starts to run bad then add higher grade to raise the octane in the tank and stick with that unless it still is running bad.

 

[joe sobo]

I'm not saying that at all. I'm just stating that its in the car's best interest to run the highest octane that you can get. 91 and 93 are great for these cars from what I've read. Any boosted car/truck for that matter. Correct me if I'm wrong but the factory fuel maps in the boosted DSMs were written to assume that the fuel being pumped into the engine was in the upper end range of octanes. Changing the octane rating to one that pre-ignites much easier is changing a factor in the calculations that the car is having trouble comprehending. Its like your TPS not reading correctly or MAP, an unaltered PCM is going to have difficulty adjusting to something it was not programmed to do.

well said

 

[GooeyGus]

The way I see it, you're looking at about a 3 dollar difference on a complete fill up. Is it worth it to put your engine into the hands of the knock sensor and hope that it does its job for $3? I dont think so.

Not to mention that it actually might make your gas mileage worse, therefore negating any cost savings over premium. The reason being that (and someone correct me if I'm wrong...) once the ECU sees knock, it will switch over to a less aggressive timing map, even when cruising. Less timing advance while cruising = less fuel economy. I'm not sure how long the ECU uses a less aggressive timing map after sensing knock. BUT, with premium you shouldn't get any knock and you'll have the most advance possible, giving you good fuel economy.

 

[Squirrel8811]

The higher the octane the higher the flash point of the fuel. (It takes more heat to ignite the fuel and compression creates heat) You want a higher grade of fuel because the turbo is packing all that air in the engine upping the amount of compressed fuel. If you dont run premium then you will have preignition causing spark knock which can damage the piston. So yes run premium like the manufacture suggests. And premium here is 91 so I think that would be fine instead of 93.

 

[etay89]

well, i'm a cheap guy. very cheap in fact. at first, i didn't think it made a difference, but then one night, i filled my tank up with 93 and it ran so much better and smoother...then i got the oil change with synthetic and it ran and accelerated like it was a new car.

needless to say, just bite the bullet and get the expensive stuff. the car will thank you later. if you don't wanna put in the good stuff, i'll gladly take your car haha

 

[knochgoon24]

There can be some reasons for N/A cars to run a higher grade gas. I have a friend with a Mazda 6 with minor bolt-ons. He had it dyno'd an they noticed it was knocking (it has a knock sensor). They filled it with 89 instead of 87 and the knocking went away. The improvement was seen on the dyno charts. He runs 89 now.

 

[bry2gdsm]

Premium Fuel Is A Must On These Cars! Otherwise The Car Will Run Pretty Bad..

 

[907gs-t]

Up here in Alaska were stuck with 90 octane premium which ain't cool imo.

 

[2gawdtsi]

Does anyone know when exactly the ecu will switch to the lower octane gas map?
All I can find around here is 91 octane, and i am curious to if 93 octane will give better performance?

what was the stock ecu originally tuned for. 91 or 93 octane, seeing how they are both premium in different areas.

 

[DSMopar]

You know I was curious about this when my DSM was bone stock, 9 psi isn't a ton of boost... however at the time I didn't have access to a logger.

In short, you can run 87 for sure if you stay out of boost completely... How much boost you can hit on a stock setup with that fuel is yet to be determined... However like they said the price difference isn't enough to justify it IMO.

 

[eclipse gsx]

damn i always run cheap gas i think ima run premium or 93 for now on thanks guys

 

[knochgoon24]

Does anyone know when exactly the ecu will switch to the lower octane gas map?
All I can find around here is 91 octane, and i am curious to if 93 octane will give better performance?

what was the stock ecu originally tuned for. 91 or 93 octane, seeing how they are both premium in different areas.

It switches based on the amount of knock it's seeing. It doesn't completely drop to the low octane map. Think of it more like a max/min deal. There's an "octane trim" that is used to interpolate between the two. So at 50% trim, it would use an average value between the two. If it doesn't see knock, it will stay at 100% and use the high octane map values for fuel and timing.

 

[2gawdtsi]

oh, i gotcha.
that makes alot more since now,
so the only way to tell for sure is to log for knock?

thank you, good information.

 

[knochgoon24]

oh, i gotcha.
that makes alot more since now,
so the only way to tell for sure is to log for knock?

thank you, good information.

No, actually there's a parameter to log using MUTII for octane level, aka octane trim.

I know evoscan has it. I haven't tried any other 2g loggers so I don't know. Anything that logs using MUTII or MUTIII should be able to log it.

You can get occasional knock and the octane level won't change. It's when there's consistent knock that it adjusts.

 

[2gawdtsi]

yeah,
iv read up some on ecuflash, and evoscan and plan on getting it in the near future.
hopefully

I've read that generally the ecu will pull one degree of timing for every 3 counts of knock.
is this when the ecu changes the fuel trim also?

 

[knochgoon24]

yeah,
iv read up some on ecuflash, and evoscan and plan on getting it in the near future.
hopefully

I've read that generally the ecu will pull one degree of timing for every 3 counts of knock.
is this when the ecu changes the fuel trim also?

No. I'm not 100% sure on the what requirements have to be met to adjust the octane level. I've never had my car knock enough to change it.

When the car pulls timing like you mentioned, it is just applying it where there's knock. The octane level applies to the the whole map.

This is about the limit of my knowledge. Someone more versed in ECU code should probably take it from here.

 

[ruben2566]

You should use 91 minimum, or 93 if available to play it safe. Using low octane fuel, will cause the timing to be pulled, making you use more fuel, which defeates the purpose of using cheaper fuel.

The lower octane fuel also causes the engine to knock sooner, and over time it adds up to flattening then spining a rod bearing.

 

[constant_proj21]

I've always used bp93 ultimate in my cars, but then again I have access to it. I would never risk using a low grade fuel, not worth my engines life.

 

[IgotBoost91]

well doesnt the higher the octance the more is does to prevent engine knock or detonation? ive always heard run super grade on turbo cars and they dont really tell you that for shits and giggles.

 

[beihl304]

you should probably spend the extra money in fuel than risk the life of the engine by going with what is not preferred.

 

[jeffo]

ok, i totally agree with what you are saying. but shockracer posted above that in his area, the highest is 91 octane...............so what?, he must tow his car to the nearest place that has 93, even if the next place is 300 miles away?

There is a good reason why the octane rating of premium varies from state to state, its called altitude:
http://en.wikipedia.org/wiki/United_States
Simple answer, you should ALWAYS run the highest octane premium available in your area in your turbo DSM. It allows the ECU to keep you at full timing advance, for the most HP.
But, that being said, if I was wickedz, just making a long cross-country drive on the highway, just blowing through many gallons of fuel, yes, you could get away with using lower octane fuel. BUT, I would turn the boost way down and stay out of the boost as much as possible. I have done that in my GVR-4 when we drove 10,000 miles out west and back a few years ago. I bypassed the BCS solenoid so that I only had 7psi boost max, and I had a knock gauge to watch, to make sure it wasn't causing any issues. You will get better mpg also.

 

[this_tsi_8urV8]

damn i always run cheap gas i think ima run premium or 93 for now on thanks guys

And you've run 11.5 in 1/4mi??? Using cheap fuel??? Unless you meant in price.

For you cheap ppl out there, you can also make the car run a bit leaner, if you have a way of doing so. I still don't see the need for it, since I get about 30mpg on the highway crusing @ 70. Just use what it was made for.

 

[Dert]

Only if you also add the "PREMIUM ONLY" sticker inside the gas door. +25hp

 

[ruben2566]

Cheap fuel is not always cheaper.