I have a 1.8t a4 b6 what should I use for gas and would it hurt it if I ran regular gas?

 

I got my a4 1.8t two years ago and have only put regular in twice, both because the gas station attendant put in the wrong pump. Lol.

Idk, I always put in premium, it's become almost OCDish. I'm not sure it makes a big difference. I'm not qualified (car knowledge wise) to make the decision. It's what a few buddies of mine told me to do..

 

It does make a big difference. Run premium gas. You have a turbo so you need it for detonation resistance. The ECU is tuned for premium. And if the extra $1.80-2.00 per full tank is that big a deal, you're in the wrong car. They specify premium for a very real reason. Use it.

 

I agree with devil that it's only a couple dollars more a tank to fill with premium instead of regular. But there should be really no tuning difference in a tune for 93/91 octane and 87 octane. The reason to run higher octane gas is the higher the octane the less chance of knock/detonation. As long as you are running stock boost levels and no modifications it would be perfectly fine to run 87 octane unless for some reason you are seeing knock which you shouldn't be. I'm not really sure on audi's if the CEL light flashes when it reaches a certain degree of knock like other cars but that would be one way to tell if you have knock. Then again as Devil said it's only a few bucks more to run premium gas so why not use it...

 

The tuning differences come into play a couple ways. Higher octane fuel is more resistant to detonation (pre-ignition). Having higher octane fuel (from a power standpoint) allows the ECU to set more aggressive ignition timing, building more power. But there's interplay with emissions and economy as well. Run the wrong octane and the car will run and drive, but not happily. The ECU fueling and timing maps, both for idle and for load, retard under boost, etc, are all set up with a specific minimum octane in mind. Going below that to save two bucks on 16 gallons of gas means the ECU has to compensate by pulling timing, adjusting fuel mixture, and in the case of high load/high throttle angle, clamp down some on the boost. The engine is trying to run but is being handicapped by the corrections the car has to make. Efficiency goes down, mileage suffers, and premature wear and fouling can result. Saving that two bucks a week for three years might save you $150 in fuel, but it can cost you a $50 set of plugs, potentially a $1000 catalytic converter, continued lower efficiency from carbon buildup internally, damage from knock if you're boosting hard, and other issues as well. Not a great deal.

Bottom line - the guys that designed and tuned the car know more. Run the gas they specify, spend the $2 a week extra on 91/93 octane, and forget about it.

 

I agree. The manual says the minimum octane is 91. DON'T GO BELOW IT. Your car WILL run like crap. You will feel it struggling. Even though the gas guage does not have premium gas written on it like in other cars it doesn't mean it's your choice of gas to use

Minimum 91 octane or you'll be in trouble with all the problems mentioned above… and maybe more…

 

Now i'm not saying in anyway that anyone should or really has a good reason to run 87 octane, but the car will not run like crap as stated above. I've put 87 in my 01 1.8t numerous times and it runs the same as if there is 93 in it. I've never done any kind of tuning with audi/1.8t ecus, but I am fairly certain it would be set up the same way as most other ecu's. I've tuned many ecu's, besides my audi I own a 600whp DSM that I tuned 100% myself. I currently run 32-33 psi on a 62mm turbo with 0 deg of knock on 93 octane. The OP's 1.8t ecu prob has 2 ignition and 2 timing maps. One for "high" octane and one for "low" octane. When a certain sensor see's that the value is at the level to switch to the "low" octane maps, the ecu will do things such as lower timing and add more fuel to prevent detonation. Your ecu will most likely never go into the "low" octane maps even if you are running 87 octane, unless you are running higher boost or boost for a long period of time at a high load. So after all that.. just run premium gas.. There is really no reason not to but if you were to run 87 or 89 octane gas it would not make your car run bad or anything just has a greater chance of knock, which probably won't occur anyway and could possibly cause the car to use more fuel than necessary if the ECU does switch to the lower octane maps. I just felt like putting my 2 cents in about tuning knowledge. Both Devil and westhive4life were correct with what they said, except for the fact that westhive said the car will run like crap which it will not... All in all just run premium..

 

ok thanks cause i let my mom drive it and she put regular in it but i always out premium in it. Now also on some of the tune software it says you can only run 93.. i have always wondered what will happen if you run premium or regular? Do you have to run 93?

 

The chips are tuned to run that much more aggressively than stock with significantly higher boost. Put in **** gas and you'll misfire and spend your days in safety boost.

The point was already made - even stock, run premium gas. With higher boost, that should be a no-brainer.

 

Sorry, I gotta do this...

$2 x 52weeks(1 year) = $104 x 3 years = $312

$312 =/= $150

That being said, and to stay somewhat "on topic," I currently and in the future will always put premium in a car that says to put premium in.