hediki12

Hey just remembered a talk i had with some friends who swore by BP gas. they realy think it makes there cars faster (evos ,hondas ,subies). I personally dont have a bp close enough to my house to try it often but the few times i did it didnt make any noticeable difference from luke oil gas station. I tried to explain that its the octane rating that is important . 93 is 93 (in mathematically) . I've never thrown knock cel switching from mobile, to bp or to luke oil(so no "watered down stuff or mislabeled gas). Does any one else have an input on this matter? I mean if i can squeeze a few extra *'s of timing by using a certain brand hell ill drive 2 cities over to get it.

kiley_sean

iTrader: (18)

IMO, I think what impacts the quality of gas more (than the brand) is the condition of the tanks under the ground (water,dirt, rust and other contaminates).

Personally, I like Shell, but will take gas from any of the "name brands" as long as the pavement looks good. If the pavement looks like it was laid in WWII...I'll take that as a rusting tank and pass.

WWIXMR

I used to swear by Sunoco's Ultra 94(94 octane) until they pulled it from us in NJ for some reason. Did make the car feel faster.
Since then I've been using Sunoco 93. It's probably all the same crap.

chmodlf

iTrader: (19)

Much of this is lingering "wisdom" from the large bro tuner... He used to go on and on about gas quality. I think it was to cover up tune shortcomings.

I saw an unmarked tanker at a shell station filling the tank. I asked him about the differences in the gas. He said that the gas itself is the same. The difference is in the additives that the various compaines use.

It is also worth noting that the octane rating is a minimum rating.

TouringBubble

iTrader: (2)

Yes and no ...

First, consider that the octane rating is a minimum rating, not a specific rating. So, 93 at one station could really be 94.5, and it could be 93.2 down the street.

Higher octane alone will never add power to a car, period. The car has to be tuned to take advantage of it, OR the car has to be running poorly on the lower quality fuel. If you are getting knock on 93 from one station and not from another, then you would see power gains.

The basic rule I follow and suggest is to get the car tuned on the fuel you will run, and from the station you will buy it from. This will yield the most consistent tune and power results.

If you're not tuned, you'd have to log the car to see how it performs with different fuels from different stations. If you see knock at one, try another.

chmodlf

iTrader: (19)

Then why run race gas? Granted there is a big octane jump but I think it is more about knock prevention than power when we are talking about variance in octane.

I agree about running the same brand for consistency.

TouringBubble

iTrader: (2)

Because you tune for it. Higher octane means better knock resistance ... which is useless if you aren't knocking. So, you turn up the boost/timing/fuel past the knock threshold of 93 for more power.

chmodlf

iTrader: (19)

Of course...What I was saying is this. Tune the car for 93. Go to a track day and put in 110. Are you going to get more power? No you will get knock protection and engine safety. Unless you want to switch maps and tune for more power on 110.

SilverShadow03

iTrader: (19)

I don't have any technical data to back up my comment BUT, when I was first tuned by Shiv at Vishnu, he was unable to dyno tune my car with the gas I had in the tank. It was apparently due to excessive knocking and breaking up at WOT....He asked I come back once the tank was empty and filled with Unocal 76.....91 Octane is the best we get in Cali and that's all he tuned on back then at least.

So..some gas is better than others...regardless if it is the same octane, IMO.

TouringBubble

iTrader: (2)

Yes. This is correct. The same applies to variances of 93. If you aren't knocking on crappy 93, you will see no performance gain from "better" 93 ... just added safety.

Well, some have better detergents and some brands/stations will simply have better quality fuel. However, octane rating is a fixed standard. In most all cases, 2 fuels measured at exactly 93 octane will perform 100% identical as far as power.

For instance, adding 10% Ethanol to Gasoline to get a final blend at exactly 93 octane will make the same power and have the same knock resistance as straight gasoline at the same 93 octane. Fuel economy will change, but not knock resistance.

speifer

After being tuned on 93 octane from a Sunnoco station, I did have issues occasionally with getting bad gas resulting in excessive knock. When I lived in Pennsylvania, I never had issues with Shell and felt they were the best. Sunnoco was my back up.

For some reason, here in Texas, I've had issues with the Shell gasoline and much better luck with Valero. I'm not sure the brand matters so much as the condition of the station's equipment, and how often the gas gets used. In western NY where nobody bought 93 octane, it was terrible, probably because it sat in the tank for months.

Switch to E85 and you won't have any problems with knock

heyzeus11

iTrader: (12)

As it has been said, maybe it is the additives, but I know when I tune on the 93 from the Shell by my house and a few days later fill up on the BP that is by me as well I pick up several counts of knock. I basically have to back off on the tune to keep it from knocking. When the tank is empty again, and I fill up at the Shell I can go back to my previous tune with no knock. I have tested this several times, I don't know exactly what the difference is but there is a difference.

TouringBubble

iTrader: (2)

I've had similar issues, but it was mostly due to Ethanol concentration in a tank I got from a specific station (Shell).

Basically, I was running 100% duty on the turbo and nearing the end of the stock injectors. I went to a track day and the car ran very lean up top. in to the mid 12's toward redline. Basically, the Shell fuel had a higher octane concentration than the BP fuel I tuned it for. I played with the tune and maxed out the injectors to get back to the high 11's up top.

I filled up at my usual BP that night and went back to the track the next day ... on the previous tune the AFRs were back to normal.

This is the reason I recommend staying with one station as much as possible.

I have seen a similar issue to you where the fuel was in check, but knock resistance wasn't as good, but I haven't been able to get repeated results ... either way, I still don't go to that station that gave me knock.

T2Small

iTrader: (1)

There does seem to be some variance, but running on the edge might not be a great idea in case your favorite station gets a tanker full of slightly less ideal gasoline.

If you have a choice in your area, switch to E85 (and upgrade your fuel system to match). I wish I had E85 here. Until then 94 octane will have to do.

_des_

iTrader: (57)

I can't run chevron gas. They have 100% gasoline which makes my car knock for some reason... I have to run atleast 10% ethonal