Regular or Premium fuel? [merged]

[Eclipse_98_RS]

Hi guys, my car is an all-stock RS, but I'm going to start doing some mods to it. Right now I just use regular unleaded gas, but when should I start going up in the octane? After intake/exhaust, or beyond that? I don't want to screw up my engine but I don't want to have to shell out more cash on fuel than I do now. I know, I'm a cheap bastage.

 

[jpolizo]

Poor mileage can be a single cause or multiple causes all adding up. It is one of the hardest things to diagose. Some things to check are:

o clutch slip
o transmission problem
o underinflated tires
o poor wheel alignment
o brake drag
o thermostat stuck open
o clogged exhaust
o mis-tuned (timing)
o burned valve(s)
o fuel leaks
o engine wear (compression too low)
o fuel pressure too high
o O2 sensor
o driving style

 

[BitAddict]

Could it have something to do with a bad air flow sensor in the maf?

 

[FrostbyteTalon]

MY gas mileage wasn't that bad but it was going down. My buddy and I did a combustion chamber cleaner (its a mopar product we bought at a dodge dealership). What you do is remove the PCV valve and turn the motor on. The car will start to stall because the PCV sucks in and with out back pressure (if you will) the car will putter so you need 2 people to do this. One to spray in the cleaner (on the hose end that connects to the pcv) and one to keep on the throttle so the car doesn't stall. Once the can is empty re connect the PCV WITHOUT letting the motor stall and let it run for about 10 minutes. Then turn it off, and take out your plugs. Clean them all very well because they get really junked up and replace them. Then do an oil change. I'm not sure, but I'd imagine my mileage has gone up at least 5-10 mpg on average since we did it like a week ago. The combustion chamber cleaner is rather hard to find but well worth the effort. I'll look into the part number. I think its like $8 per can.

 

[Jeremoose]

Quick stupid question all: does a '96 TSi AWD "require" Premium (Supreme)?? or will it run fine on regular?? Thanks.


P.S. I searched for this, but i couldn't find anyting...

 

[nutshot]

My car runs poorly when I achieve boost on low octane.

 

[Gigaah]

Being turbo charged the excessive heat and pressure created make the process more suseptable to engine knock. Higher octane gas helps prevent knock because the higher the octane rating of the gas the less likley the fuel mixture is to ignite when its not supposed to(knock). That is why it says you should run premium fuel. Even at stock running conditions I agree premium fuel is safer for the car. But hey..if you can run regular and log acceptable knock I'd say go for it and use regular gas!

 

[leet]

At the VERY least, 91 octane.

 

[Defiant]

Okay, nobody whisper a word about this, but mine can drop-kick its way up to Tahoe in the summer on regular just fine. It's not a leisurely drive.

But then, the Owner's Manual also says to not use fuels that contain MTBE, too, so what the eff.

 

[Jeremoose]

Very helpful guys: thanks!! BUT, its not going to like DESTROY my car right?

 

[dsmayhem]

The gauge cluster says "use premium only" just to mess with you.

 

[Gigaah]

Naw you should be ok. I didn't check your mods though.
If you have a logger couldn't hurt to check the knock, any additional knock for the lower octane is the only thing that would cause harm to your engine.

 

[Jeremoose]

Thanks a lot guys!!! Super-helpful, and FAST responses too ... By the way, i don't have any mods YET, i'm just going to pick it up tomorrow!!! its about 5 hours away and i'm gonna drive it home with Regular in it, so i'll let you all know how it goes!!! And i'm sure there'll be MANY more questions to come

 

[kyledykstra]

Thanks a lot guys!!! Super-helpful, and FAST responses too ... By the way, i don't have any mods YET, i'm just going to pick it up tomorrow!!! its about 5 hours away and i'm gonna drive it home with Regular in it, so i'll let you all know how it goes!!! And i'm sure there'll be MANY more questions to come

That's what I do when I'm going on a longer trip where I'll be burning a lot of gas. I don't see the need to pay for premium if I'm just going to be going 75 MPH for 6 hours straight.

 

[Jeremoose]

Good news all: I got my TSi today, its drove AWESOME, its really clean, it ran great on regular and i love it !!!! I think i'm in heaven Pics will be comin soon! Lata

 

[a_scobel]

I use the middle octane available at the pump.

 

[MrDee]

while on the Gas issue..is it correct to say a lower octane gas will give you more carbon over high Octane?

 

[Defiant]

while on the Gas issue..is it correct to say a lower octane gas will give you more carbon over high Octane?

No, just the opposite. However, most carbon deposits come from oil burning issues.

 

[Jeremoose]

Again, back onto the gas issue: I found that its a lot cheaper to fill with regular and then buy one of those Octane Booster's.. That's what my bro did with his stealth and he said it ran better than with premium... Any thoughts?

 

[its_hey_ma]

Thier is alot of articles all over the web about octane boosters, both store bought and home made, but from what i understand the store boughten ones raise your octain 1 point for every 4 bottles used. The homemade stuff is not only cheaper, but you can make as much 'octane points' as you want. It works great on my daily driver/ parts getter car, V8 caprice, but I'm a little scared to try it on my RST Laser. If you can find any info on that working for turbos with no probs I'd go that way

 

[Jeremoose]

Ah, cool thanks... I'll see if i can find any info on that homemade octane booster..

 

[crankbender]

Many people use toluene to up the ocatane....they actually use to use it in f1 if you remember them talking about rocket fuel...

Anyway you can burn lower octane gas and it will actually be cleaner for your engine. Where you will run into problems is under full boost when you are approaching detonation. You may not notice any change, you may notice a little loss in power, you may detonate and blow up your car. None of us can tell anybody else what will happen with there engine because we don't know the condition inside. Just be aware of this and log it to see if you get knock under wot when using the lower octanes.

When not at WOT or full boost you should actually run better on lower octane gasoline.

 

[67goatpimp]

You need premium gas, don't get on it without it. If you have a LONG drive ahead of you, fill up regular and just cruise but stay out of the boost and get as low as you can before you fill up with Premium again. On a side note, if you're building a performance car and you can't afford the extra two bucks at the pump to keep your baby (that you keep throwing money into) from knocking...something's wrong with this picture. Just my $.02

 

[Jeremoose]

Well, as soon as summer rolls around, this won't be a problem... I just didn't want to fill up with premium in the winter while I'm putting around. But, in the summer, Premium it is!!!

P.S. I don't know why I car so much anyways, my parents gave me a gas-card for while I'm going to college

 

[Defiant]

P.S. I don't know why I care so much anyways, my parents gave me a gas-card for while I'm going to college

Ah, so they'll be learning something during the same time you are. The poor fools. AM/PM, $11/24.

 

[Jeremoose]

, yeah, that's probably true..