road trip coming up.. gas?

[S4evr]

ill be driving home from college in a couple of days (6-7 hour drive) and in spite of damn high gas prices, is it alright for a stage 3 car to run 87/89 octane to save some money? i wouldnt be boosting eitherway due to a bad clutch, so would low octane be ok?

[AMC]

i messed up my EGT's and 02's when i forgot to put 93 and put 87 by accident. 91 is the lowest ill go

[wheel366]

I put 87 my mistake and ran it the full tank. I put my chip back in stock mode and didn't run hard. I haven't noticed any problems and when I was almost empty I put in 93.

[ThirdStrike]

op dont do it. you will save what...5 bucks a tank? its not worth the risk.. even in stock mode in heat you will probably detonate

[sCeRaXn]

Personally, i wouldnt do it. But i dont think it will hurt anything if you dont boost and drive like an old woman. I dont see how it would hurt your 02's or egt's, because these same parts are in lower model cars that run perfectly fine on low octane. Its a low compression motor that isnt near lean under normal driving conditions, so you shouldnt have any problems with detonation. Like i said, i wouldnt do it...but you should be ok. If you decide to get heavy on the throttle because a vette is messing with you then dont blame me when your motor blows lol.

[saucys4]

long story short: my GIAC flashloader had the ECU on RACE as i was using 91 craptane for more than a tank. didnt feel unusual and my O2's are still fine.

[ThirdStrike]

^LOL
yah that wont hurt your motor at all. dont worry op you will be fine

[Dimcorner]

I averaged 24.5 mpg on a 900 mile trip at about 70mph.
Getting 89 octane will save you 30 cents or so per gallon. 14 Gal tank... $4.20.
You won't save that much.

[VinNyS4]

its not worth it for a few bucks just go 93, 91 is the lowest i would go ..If you are able to afford a s4 you should be able to spare a few extra bucks.

[FrimmelNoJerz]

uhh...

[SoEvoL]

wouldnt you lose gas mileage running cheaper gas or is it just me. if you wanna save on gas dont drive it like you stole it, and run the speed limit. you can stretch a tank further going 65 than you would going 75 or whatever.

[S4evr]

wouldnt you lose gas mileage running cheaper gas or is it just me. if you wanna save on gas dont drive it like you stole it, and run the speed limit. you can stretch a tank further going 65 than you would going 75 or whatever.

that was my thought i wanted to see if anyone else came up with that too..

i guess i will run 93 all the way home then.

[Dimcorner]

Accelerate going down hill, bleed a little speed going uphill. Also going up hill get behind a draft.

When getting off the ramp, just let go of gas and coast to stop. If you can anticipate the ramp you can get off gas sooner. That 24.5mpg average included 3 days of Miami city driving... Highway only i was peaking at 30mpg. Just take it easy when driving.

[sCeRaXn]

wouldnt you lose gas mileage running cheaper gas or is it just me. if you wanna save on gas dont drive it like you stole it, and run the speed limit. you can stretch a tank further going 65 than you would going 75 or whatever.

How would you lose gas mileage? Im not saying youre wrong, im just trying to see how that would be possible. The car will be running the same fuel pressure and same injector duty cycle, so there wont be any increase or decrease from that. If its running stoich then the 02 should see very similar, if not identical readings, so it shouldnt compensate by adding more fuel. In normal driving lower octane gas will burn easier and more completely than a higher octane gas. Maybe im missing something.

To the OP...im not saying you should run 87oct at all. Like i said in my previous post, i wouldnt do it. Im just trying to figure out how yall came up with this.

[Jurjen]

op dont do it. you will save what...5 bucks a tank? its not worth the risk.. even in stock mode in heat you will probably detonate

And what if you run into a Z06 or 911 that needs to be shown who's boss?

[Charlie]

What you would save on gas wouldn't Equal to the amount of damage you cause to you car because you want to save 14 cents a gallon.

[Dimcorner]

How would you lose gas mileage? Im not saying youre wrong, im just trying to see how that would be possible. The car will be running the same fuel pressure and same injector duty cycle, so there wont be any increase or decrease from that. If its running stoich then the 02 should see very similar, if not identical readings, so it shouldnt compensate by adding more fuel. In normal driving lower octane gas will burn easier and more completely than a higher octane gas. Maybe im missing something.

To the OP...im not saying you should run 87oct at all. Like i said in my previous post, i wouldnt do it. Im just trying to figure out how yall came up with this.

With lower octane if the car starts to knock it probably would retard timing and then your acceleration would suck. Which would mean you have to hit the gas more to accelerate.

[smaggs]

just fill the tank up with 93, Our cars are very good on long distance drives with no boost. When driving from Canada B,c vancouver to L.A Cali I averaged 500-600km to a tank. And please do NOT do 87

[exorcet]

With lower octane if the car starts to knock it probably would retard timing and then your acceleration would suck. Which would mean you have to hit the gas more to accelerate.

exactly.. all things equal (mileage) it's still not worth saving $5 / tank. We're talking $10 total the whole trip.

Realistically, you will see more power, and better fuel efficiency with the 93, and the increase in MPG would offset any additional cost (which shouldn't be considered additional because you should run it anyway).

[DonnieD]

Northern California - Bay Area's Gas stations only offer 87, 89, and 91! What gives!!!

[sCeRaXn]

With lower octane if the car starts to knock it probably would retard timing and then your acceleration would suck. Which would mean you have to hit the gas more to accelerate.

First of all...if your car is detonating DO NOT HIT THE GAS HARDER!!

Second, if youre driving like a normal human then the car shouldnt detonate. Higher octane does NOT mean more effeciency in most cases. The octane rating is only the ability to reduce knock, and it does this by actually making the flash point of the fuel higher...therefore you actually get a more complete combustion when using lower octane. Now, all of this goes out the window when youre talking about racing or even "spirited driving" as youll need that extra protection against knock...but normal driving(and no boost) youll see no real advantages with higher octane.

As smaggs said, our cars really arent that bad on long highway trips. The amount you save isnt enough to justify not being able to hit the gas to get in front of a slow moving car, or if someone wants to have a run on the hwy. Id go with 93 oct if i were you...but if youre really that strapped for cash then put in 89 and granny the car and you should be fine. Whatever you do...DONT GET HEAVY ON THE THROTTLE!

[SoEvoL]

i suppose in theory you could run a lower octane gas just fine, but you would have to do a zero boost drive cycle to stay out of any danger, so if you had to drive hard or do something that required heavy accel you would be risking your car. not to say your car will blow up, but whats saving a few bucks when you can risk losing a engine? im no penny pincher so ive always used 93oct even on my supercharged gsr, with lower octane the car just runs like crap and my compression is way to high to make me feel comfortable. its true your audi will be able to compensate if the knock sensor detects something and it will retard your timing... to an extent. your car is designed to run a certain octane and its engineered for it, now you have a stage 3 setup, the octane doesnt lower obviously, i would be even more meticulous about it...... i wont get into detonation and preigition, but heres a article discussing them and other engine basics.

http://www.contactmagazine.com/Issue...ineBasics.html

i wouldnt risk it, just my 02 cents

[quickdub]

"therefore you actually get a more complete combustion when using lower octane." = FALSE

Higher Octane fuel burns more complete. Lower Octane fuel burns more uncontrollably, which is the meaning of "knock" or better known as "pre-ignition"

With higher octane fuel your engine can take advantage of more advanced timing, especially under no-load (highway) driving, which leads to a more efficient combustion cycle. Timing is key when you're looking at maximizing efficiency...

[b5s4tt]

i did it once in the auto s4 just to see what would happen. it wasnt bad really, but i didnt really beat it. but it did ping which i didnt like. i wouldnt recommend it though

[sCeRaXn]

"therefore you actually get a more complete combustion when using lower octane." = FALSE

Higher Octane fuel burns more complete. Lower Octane fuel burns more uncontrollably, which is the meaning of "knock" or better known as "pre-ignition"

With higher octane fuel your engine can take advantage of more advanced timing, especially under no-load (highway) driving, which leads to a more efficient combustion cycle. Timing is key when you're looking at maximizing efficiency...

Higher octane fuel burns more complete at higher cylinder pressures and temperatures. Have you ever wondered why putting 93 in a car that only calls for 87 will gain NOTHING? Because when putting around town(which is what any car running 87 would be designed for) 87oct gives more than enough knock protection. This is exactly what would happen if you were putting around town in an s4 with lower octane fuel. The only thing that would change that would be higher compression, advanced ignition timing, REALLY aggressive cam timing, etc...which is usually only found on high performance all motor cars. Under normal driving and out of boost, the s4 motor acts just like every other lower compression gas saving motor. Theres nothing that would cause knock under these situations unless there was something majorly wrong with the car.

I agree about the advantages from timing changes with high octane, but most people with these cars dont have the software to change timing enough for it to make a difference. To those who can, this would be a good option for more complete combustion and lower cylinder temps. If you cant tweak the timing then i still say you wont see any difference in octane. Once again...this is only talking about driving normally(like the op was talking about).

BTW-Pre-ignition is a FORM of detonation...it isnt the cause of all detonation. Pre-ignition is when the gas is ignited before the spark plug fires. Once again, this isnt something that would happen under normal driving conditions unless something was wrong with the car. Its usually caused by high cylinder pressures(boost or high compression) and/or temps, but can be caused by other things as well.

[aaaudiprotein]

I understand your situation, but u gonna save prolly 15 cents on each gallon going with 89... Maybe it is better to save up those $5 on something else??? :)))

[OldYella]

You could run a mix of cheaper e85 (about 30%) or less and run 87 and i wouldn't think you would run into problems. The problem would be finding the station.