Regular v. Premium Gas

**jkf243** · 04-30-2006, 07:58 AM

I was wondering if anyone has tried using regular gas in their 04 GTO for daily driving. I know that in the past using a lower octane caused knocking but have heard that you don't have to use premium in today's computer controlled cars. Sure, HP will have to decrease some but I wondered if anyone had tried it and how it affected the car. The only reason I'm asking is that I might have to start driving 50 miles a day for work and am not sure how excited I am about having to pay for premium when I get my GTO.

Thanks,
James

**Pulse Red GTO** · 04-30-2006, 03:29 PM

I haven't yet, but I also just started driving the GTO again after the winter. This weekend was the first time I was driving it & it still has premium in it. I will let you know however, b/c I am going to try it on the next tank, I have never ran anything other than premium in it though so far

txcosmos · 05-01-2006, 11:22 AM

Depends if you have a tune on your car or not. If you do, most likely it has been tuned only to accept the higher octane to eliminate detonation (knock).

If you are running a stock car, the PCM will make some changes because of the lower octane.

As long as you are not running it WOT throttle and getting into it too bad, it should be OK on a stock car.

**Jason05GTO** · 05-02-2006, 02:05 AM

I dont, every now and then Ill mess up and put mid-grade in there - but generally its 93.

**Wesman** · 05-02-2006, 12:44 PM

I just put premium (93 octane) in my LS1, haven't tried anything less. It says "Premium Fuel Reccommended" in the gas door, so thats what I go with.

I wonder how much power/fuel mileage it would lose with 89 or 87 octane??

**camarozzzcamaro** · 05-04-2006, 07:37 AM

I always use 87 octane. and i drive my 04 year round. No knock problems here.

**jkf243** · 05-04-2006, 09:06 AM

Do you notice any drop in performance or mileage with 87? Glad to hear there's no knocking.

**01SSto05GTO** · 05-04-2006, 09:29 AM

I fill up once a week and usually get about 15 gallons. If you use the typical +$.20 for premium it works out to $3 more per tank. That works out to $156 more a year for 52 tanks. It's not worth using the lower grade stuff so thats why I use premium.

**AUSI GTO** · 05-04-2006, 01:58 PM

My thoughts on this is if you want to use cheaper fuel then buy a cheaper car.........These performance GTO's and many other late model performance cars were designed, built and they do require the type of premium fuel that is suggested. GTO's would not have a decal on the fuel filler door that states to use premium fuel if low or mid grade fuel was acceptable

**jwulf** · 05-29-2006, 06:28 PM

Hi,

From waht i have learned from the Grand Prix Forums, if you use regular in the GM "Premium reccommended/required" cars, the regular gas will cause knock which is very destructive to the engines. in the GP's the pistons tend to fail with high KR.

JW

Hoping to get 05' Yellow Jacket GTO very soon...

**Wesman** · 05-29-2006, 06:43 PM

Originally Posted by jwulf

Hi,

From waht i have learned from the Grand Prix Forums, if you use regular in the GM "Premium reccommended/required" cars, the regular gas will cause knock which is very destructive to the engines. in the GP's the pistons tend to fail with high KR.

Hence the reason they have knock sensors

The sensors detect if the fuel is pre-igniting, and can retard the timing and cut power so that engine damage does not occur. So basically you will loose power and fuel economy, but at least your engine won't blow up.

**jacobyb** · 05-30-2006, 01:27 AM

All modern cars that require premium fuel acn use 87. Even high-end exotics. The ECU will remove timming and enrich the air/fuel ratio. You will lose power, some have stated up to 40hp, and you will get worse fuel economy.

So, you can use 87 and pay less for the fuel, however you are going to end up using more fuel to go thesame distance and that is going to eliminate any advantage you would have in terms of saving money at the pump. You are also going to have less power to show for it.

Think about it realistically. When I fill my tank it usually takes about 15 gallons. Filling with premium means that I am paying a whopping $3 more to fill with 91 then if I was going to fill with 87. hen you are spending $50 to fill your tank, is another $3 going to break you? Honestly?

**454 FTO** · 05-30-2006, 02:29 AM

The ECU contains two advance maps for high ocatne and regular. In past models, both of these curves have been found to be rather conservative. The important thing is do you like having full power available? Besides, a tankfull of good fuel is only a few bucks dearer.

**jkf243** · 06-05-2006, 07:28 PM

Hey guys, thanks for the answers to a kind of silly questions. After really thinking about it I decided that if I was going to buy a performance car I should use the high test gas! Luckilly, I don't think I'll have to drive 50 interstate miles a day anymore and I'm keeping the GP so this should be less of an issue. I suppose if gas goes up a lot then the goat will get parked more often and the GP will be used. Thanks for all the good info. I appreciate everyone's comments and opinions.

**third_shift|studios** · 06-06-2006, 12:19 PM

TO my knowlege, lower octane detonates at a higher temperature, creating more heat, creating more stress for the engine.

**Wesman** · 06-06-2006, 08:31 PM

Originally Posted by dipherentdesign

TO my knowlege, lower octane detonates at a higher temperature, creating more heat, creating more stress for the engine.

Not quite.

Lower octane detonates at a lower tempurature and under less pressure than higher octane fuel. This causes pre-ignition (knock), poor emissions, less power, lower fuel economy, and can even damage the engine if you don't have a computer controlled vehicle with knock sensors.

Bottom line - Use Premium fuel if the manufacturer reccommends it

**Pulse Red GTO** · 06-07-2006, 06:52 AM

My brother had a 00 & 02 Camaro SS & never used anything other than 87 in either of them & never had a problem! I used 87 in my 02 WS6 since it was new & never had a problem with it. No on the 04 GTO, I have always used 93 from Shell in it except for this last tank I used 87 by mistake & looked like I got better MPG actually!

**fantomx** · 06-07-2006, 02:55 PM

If your manual or gas cap states 'premium recommended' - that means you can use a lower grade.
If it states 'premium required' - that means you MUST use premium fuel and you will damage your engine. I have used 87 a few times in my Z & I heard slight knock and pink and some decrease in performance. I use 93 Octane 99 % of the time.

nhra_ta · 06-09-2006, 04:55 PM

Hello.
First, I guess I should introduce myself as I joined, but have not posted yet. My b/f and I have an '05 MBM GTO. When we bought this I sold my '02 NHRA edition Trans Am. So far, the GTO is stock, hopefully we'll be able to start getting some mods next year.
Now, for the reason I chose this section for my first post. We have about 1/3 barrel of VP C16 fuel in the garage that was for my b/f's racecar. He sold the car so now we have nothing to do with the fuel. I was wondering if we could possibly mix a small amount of that with 87 octane in the GTO or if that would be a very bad idea. It's such a waste to have the C16 sitting in the garage and paying rediculous prices for premium if we could mix our own.

We'll build another race car someday, but that's a few years off.
Any thoughts or advice on the wisdom of doing this would be greatly appreciated!

Dawn

**QuickSilverGTO** · 06-13-2006, 10:09 AM

I put 87 in my 05 one time to see. It had spark knock really bad. I had to put 104 octane booster in it to get it to stop knocking. From my experience wouldn't put anything lower than 93 in. I agree with 1badcobravert you want cheap gas buy a cheap car. It cost money to go fast!