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Premium fuel required!?

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Freebeer187

Freebeer187

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I was washing my 01 GTP today and when I opened the gas cover, I noticed a sticker that says "PREMIUM UNLEADED FUEL ONLY"

...Im like WTF! Nooo! Premium is $4.50!

I have been putting reg in there since the day I got the car. No problem that I can notice.

So whats the deal with premium only? Is it harmfull to put regular in there? Please enlighten me about this whole premium only deal.

Thanks!
 


Without Premium fuel, your more than likely experiencing pre-detonation when your engine is under boost or under load. That is a bad thing and can cost you a new engine. You should only run regular unleaded if you have tuned your car to run on it. I for one, would never put anything but premium in my tank since it only cost $3 more a tank. It would take a lot of $3 savings to = a new or rebuilt engine.

If your modded at all and have been running regular, I would be surprised that you haven't chipped a piston yet.
 
JJ91284 said:
Without Premium fuel, your more than likely experiencing pre-detonation when your engine is under boost or under load. That is a bad thing and can cost you a new engine. You should only run regular unleaded if you have tuned your car to run on it. I for one, would never put anything but premium in my tank since it only cost $3 more a tank. It would take a lot of $3 savings to = a new or rebuilt engine.

If your modded at all and have been running regular, I would be surprised that you haven't chipped a piston yet.
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Your right. I had no idea that the car needed premium. I was a little shocked by that. I will from now on run premium. Also the car is stock.

Quick question about premium for my car.

Will it improve gas mileage? I see people saying that get 23-26 mpg when no matter how granny I drive, I still am under 21mpg.
 
Freebeer187 said:
Quick question about premium for my car.

Will it improve gas mileage? I see people saying that get 23-26 mpg when no matter how granny I drive, I still am under 21mpg.
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I don't think so, but I could be wrong. Unless you have been running the 10% ethanol. If you have then you should see an increase in gas mileage. If I was you I would do a tune up on your car. Change things like fuel filter, air filter, plugs, wires, O2 sensor. That is if they haven't already.
 
Not sure if you will notice a change in MPG

Your PCM has a high octane spark table and a low octane spark table. When using regular gas it will use the low octane spark table to prevent knock. Many people have used regular gas on stock s/c V6's without issue. Since the low octane spark table has greatly reduced timing versus the High octane table you notice an increase in performance switching to premium.
 
Andrew_99GTP said:
I don't think so, but I could be wrong. Unless you have been running the 10% ethanol. If you have then you should see an increase in gas mileage. If I was you I would do a tune up on your car. Change things like fuel filter, air filter, plugs, wires, O2 sensor. That is if they haven't already.
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Just had a small tune up the other day. Replaced old PMK (something like that, i forgot the name) plugs with AC Declco plugs. Also cleaned the fuel injectors and intake manifold. Put a drop in K&N filter in about a month ago. Oil is good too. After the tune up, the car just runs great (it did before but now its even better). It gives a real smooth ride with a little pick up too.

IndeedSS said:
Not sure if you will notice a change in MPG

Your PCM has a high octane spark table and a low octane spark table. When using regular gas it will use the low octane spark table to prevent knock. Many people have used regular gas on stock s/c V6's without issue. Since the low octane spark table has greatly reduced timing versus the High octane table you notice an increase in performance switching to premium.
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I didnt know that about the low/high spark. I have about 2 gallons of reg in my tank. I have a long drive tmw (about 30 miles on the high way) so im hoping to burn up whatever I have before that trip and fill it up the premium.

Thanks for all the help!
 


I personally think the pcm still adds to much timing under the Bad Fuel SPark table. If I recall correctly, the pcm (97-03) adds around 8 degrees of timing under full load on the BFST. Under the 04+ grand prixs, the pcm pulls the timing to like 0 under full load under BFST. I uploaded an 05 comp g timing tables to my gtp and the cruise timing was increased from around 30 to 44 degrees of timing. While running on low octane fuel it drops the timing way more than my 97 bad spark table. The 04+ gtp's say you can run on regular fuel but your power will be reduced and that would be partially because the timing was pulled
 
It is safe to say that when you run higher octane fuel, you will get worse gas mileage (unless you have a tune other than stock).

Further, I feel ya on the bad gas mileage - my 97 GTP only gets about 21-23 MPG mixed city and hwy driving. It would be nice to get the 25-26 MPG like the other fellas on here.... but I'm working on that.

Good Luck!
 
I am getting 29mpg with my regal now and running 89 octane with 10% ethanol. I hope I can squeeze some more out of it though.
 
i will say this-- i know of a daily driver stock 99 regal gs that has had a pretty steady diet of 87/89 octane most all of its life, and it's at 187K miles.
 
so your saving yoour self less then 4 buxs.

Spend the 4 buxs and add what it needs. Its going to take 4-5 tanks to fully get the full octane back
 


Depending on your driving style, you should see an increase in MPG by running premium, but probably not a ton. When running off the Low Octane table, you would have to give it a lot more throttle to get the same power, but since the higher octane burns less effective, it might even out.

Running low octane and low timing is also going to increase EGT's which could lead to valve damage or cat overheating.
 
Higher octane fuel does NOT burn less effective. Once ignited, it burns the same or faster than low octane fuel depending on the blend of gasoline used.
 
"Burns less effective" was the wrong term - that's not what I was implying, so sorry for any confusion. I should have explained:

By running high octane, the higher timing table will increase IPW's depending on load. However, efficiency for power should be increased, so loads should be less than running low timing. Just depends on how you drive. ;) I would also suspect that warm-up is slightly increased with higher octane, and fuel usage could suffer, but that is just a guess.

Bottom line is, this engine was designed to run high octane to maximize burn efficiency under the factory timing settings that give the advertised HP. You will get best performance and mpg by running the recommended fuel and driving conservatively (if possible :D).
 
i run premuim but the first fill up "about 3 weeks ago i accidently didnt read the manual or door sticker and put about 3/4 87 octane. oppps lol i added all premium 93 today.
 


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