Fuel "Quality" vs Octane Rating

[Audi Junkie]

Does octane equate with quality? Say, is buying a "premium" fuel at a generic (not-top-tier) pump carry any promise of good quality in terms of deposits? To say it the other way, is low octane top-tier good "quality", again in terms of deposits?

So, let's say you have a vehicle that takes "super" and suffers from deposit formation. For the same cost, would it be "better" to run TT 89 or better to use other brands, like Sunoco or generic 91? I don't mean in terms of performance, just what is better for the engine. You could even say, generic 93 vs TT 91 or whatever.

I just want to ask really in a general sense, is generic premium as clean as TT lower octanes?

The way I always understood it is that all grades of a brand have the same quality. Super has more detergents to compensate for it's "slower" burning.

The reasons I'm asking is now I have the ECU chip for my VW 2.0T. I can switch for stock 91, 93 and 100 octane. It screams on 91, which is sufficient for my needs, but super is sold as 93 here, with the exception of Sunoco, who has 91. Other option is generic 93, or a mix of TT 89 and 93.

Just kind of confused how I want to proceed. TT 89 is cheap, +10 cents. TT 93 is +30 cents. My mfg calls for TT gas, but I can get generic 93 for the same as Sunoco 91, +$.20c.

 

[justinf89]

top tier gasoline is better than octane. Not all cars are designed to run on higher octane. It takes a more robust ignition system to burn the higher octanes so don't run premium if the car doesn't call for it. You could actually lose power because it will not burn completely. So back to the question, I don't think top-tier and octane are really comparing apples with oranges. If you can afford it, run sonoco or whatever you like, but don't put premium in if the car calls for regular.

 

[Audi Junkie]

The car has yet to run bad on any gas, but calls for 91. Now I have the chip that can use 93. 89-91 is sufficient, run on the 91 ECU setting. It does run really well on TT, but also on the generic 91 and def the 93.

So, are we simply saying that lower octane TT is a better bet?

I find buying 93 TT every time to be overkill for the short drives I do as well as the longer hwy runs.

 

[JHZR2]

Octane has no relation to quality in terms of commodity product. Amoco used to have a separate ultimate line that supposedly went through extra hydrotreating to ensure low sulfur and product quality, but that was an exception.

Some refiners do produce a higher quality product range overall, for example the irving refinery produces a better quality product than others. Hlwever given the commodity nature, that base product may as well be sunoco, mobil, etc at the distribution level.

There are some theories that the slight differences in volatility of 93 octane fuel could lead to deposits in engines where the injection and ignition arent optimized to its combustive properties - but I dont know that this is proven.

Some end product brands may be better additized, but this is dependent upon the station, etc., as the product will come from the same one or two refineries.

 

[dtt004]

Top tier gas means it's good gas. However, it also means it has been tested and approved by manufacturers in order to be called "Top Tier." Some automotive manufacturers don't belong to this circle, and some gasoline retailers are too small to have sufficient funding in order for their gasoline to be "certified."

In this sense, when a gas is Top Tier, it's a safe bet that it's good gas for any car. However, when a gas is not Top Tier, it's important to think to yourself..."this gas is not certified as Top Tier, but doesn't mean it's bad gas."

Just like GM coming out with that craziness that is Dexos. Auto companies want a cut of the profits too (in application to the Top Tier gas standard of testing)

So. The rule is that for your car, a Top Tier gas is a good idea. But when a gas is not Top Tier, it's not bad gas...but it could be...or it could not be. It simply hasn't undergone the testing set forth by the standards/automakers.

Why does Ford recommend BP when BP is not considered Top Tier? Although I do not drive a Ford, own one, or work for them, it's pretty safe to say that they wouldn't recommend bad gas...right?

All gas sold needs to meet the minimum EPA standards for detergents.

Oh and by the way, in my own personal opinion (if it matters) 89 octane gas is really pointless. I think they came out with that thing as marketing simply because most people don't want to put in premium, but think that 87 octane is "bad." Either you have a high compression, forced induction, etc. engine which requires 91, or you have a low compression, naturally aspirated engine that requires 87. I think it's a waste of money. But that's just my personal opinion.

Oh and we design cars nowadays to cope with variances in octane. I'm pretty sure you'd have to try pretty hard to destroy your engine if it requires Premium and you put in Regular. ECU's are designed to cope with this. I do not have any experience with a "chip" or whatever but I'm sure all the thing does is change the fueling and ignition timing. Maybe the margin for error is narrower.

Regardless. A real world example for you. I have a 2005 Acura NSX. I put in 87 octane, 89 octane, and 91 octane in it before. These are the 3 grades in Southern California. Then again, it has what I would call a normal compression ratio (10.0:1) and is naturally aspirated. I also drive slow if that matters. Nothing really changed. The ECU in the car does the homework for you. I don't recommend what I do for what you do. It's a matter of choice really.

I have a 2004 ZX-10R. Now things are a bit different. The ECU in the bike cannot compensate as much as the ones in a car because the ignition loop is different. It also runs a 12.4:1 compression ratio. I have put in 87 octane in it. It knocks a little bit, and is audible at idle. Then again, bikes always have a bit of a rougher idle because the cam profiling and ignition is different. And almost everything on a bike makes noise. However, I just rev it higher :] woops noise goes away.

I think I got off topic though. haha

 

[tomcat27]

My understanding is that many of the fuel suppliers share a common depot - and that the base product is litterally the same product, with a bottle of (brand specific) additives added as they fill the tanker. with the exception of BP Ultimate.

 

[motorguy222]

Gas

 

[exranger06]

Gas is gas, more or less. The brand doesn't matter much imo. I always simply go to the station with the cheapest gas, name brand or not. Never had any problems, or even noticed any difference in driveability for that matter.

 

[spasm3]

i run 87 in my avalanche except when i tow my 5000lb tt. I run 93 octane when towing. I'm not sure why, i have just always done this. Anyone else ? should i tow with 87 octane?

 

[JustinH]

Here is one for you. Mobil was recently added to the "Top Tier" gas list. Until then we have never had a "Top Tier" gas station in the area, no shell, nothing like that.

I work nights, and on my way to work I see the trucks filling up the tanks for Mobil. I have bought my gas there for years.

It is the same trucks providing the same gasoline. Its not mobil tankers providing the gas, it is a generic gas truck that I have watched go to several other gas stations on the same road.

I think a lot of this Top Tier is marketing. If you pay enough, you can get some of your gas tested, and you can get your certification badge.

I noticed that none of the gas stations are touting Top Tier, and Joe Consumer has no idea what the program is.

I buy my gas at the Mobil weekly. It costs almost a dime more per gallon, but I don't mind because it is a block from my house. It is an up kept station, and I have never had a gas problem with them.

 

[Audi Junkie]

I just don't want any regrets if I buy cheap super 93 over TT, mixed to 91-ish or Sunoco 91, which I get cheap from a rebate programme. My grocery shopping card is loaded to get $.60c off right now, usually less though.

The jist of the posts so far is that there IS NO difference in brand quality...?

All I care about is intake valve deposits on my DI turbo. I understand low grade gas may be to blame, when it flashes off the hot intake valves during VVT overlap.

 

[getnpsi]

2006 ranger gas cap says "Ford recommends BP." Where I live we do not have BP stations, but Arco Is part of BP. Arco is not top teir.

Call it cloudy logic, but more expensive cars tend to fill up at top teir places. So--I know when I fill with premium at the same locations my gas will be fresher than a 91 octane at a discount station where much less people will choose that flavor. Good enough?

 

[exranger06]

Originally Posted By: spasm3
i run 87 in my avalanche except when i tow my 5000lb tt. I run 93 octane when towing. I'm not sure why, i have just always done this. Anyone else ? should i tow with 87 octane?


I don't see any reason to use 93 octane in that truck. The engine isn't gonna magically increase the compression ratio because you have a trailer hooked up. It was designed to run on 87 under all conditions.

 

[Shannow]

Originally Posted By: justinf89
It takes a more robust ignition system to burn the higher octanes so don't run premium if the car doesn't call for it. You could actually lose power because it will not burn completely.


ummmm....no

 

[Audi Junkie]

Speaking of BP, since they pulled out of my market, there are a lot of generics taking their place at the same stations. Those tend not to be discount gas places, more like full-service quickie-marts. Along w/them, there are generally a lot of generic stations now. I almost have to look for a branded station besides Sunoco or the TT retailer we have, "Turkey Hill" which is more of a convenience store. Turkey Hill is everywhere and is relatively cheap, but they don't offer 91, just 93 at a +.30c premium.

For instance, TT 89 is $2.679 but I can get generic 93 for $2.739. TT 93 is $2.87, thus the temptation to blend it 50/50% with TT 89 to get TT 91 for $2.779....which sounds like a good compramise.

I used to go through a lot more gas then I do now, so maybe not a big deal, but my roadtrips to the city can get expensive. I don't mind changing to lower octane for trips and mixing for desired 91. Am I crazy?

All I need is a few extra mpg to make up for the super cost. That's not easy at a +$.30c premium, requiring an extra 3 mpg to break-even....a 10% gain...yikes, don't expect to see that.

 

[Quest]

Originally Posted By: justinf89
It takes a more robust ignition system to burn the higher octanes so don't run premium if the car doesn't call for it. You could actually lose power because it will not burn completely.



http://www.faqs.org/faqs/autos/gasoline-faq/part1/

part 1 to 4.

Also note: automobile grade gasoline sold in Continental North America have been standardised all across the board in terms of calorific content, burning speed, etc. The differences are into additives for antiknock (octane), detergency, etc.

 

[getnpsi]

Also would like to add that many pre-oil crisis engines had high compression using iron cylinder heads. The ignition systems were nothing great. They needed the octane to run even in light load conditions due to the 10-11-12:1 ratios, something that is getting to be more commonplace now but it took 40 years of technology and using better materials in everyday engines to get there.

 

[eljefino]

Originally Posted By: getnpsi
Also would like to add that many pre-oil crisis engines had high compression using iron cylinder heads. The ignition systems were nothing great. They needed the octane to run even in light load conditions due to the 10-11-12:1 ratios, something that is getting to be more commonplace now but it took 40 years of technology and using better materials in everyday engines to get there.


+1 "regular" leaded gas was 89, why that grade stuck around.

I'd be very curious if the TT 89 came from its own storage tank. Wonder how the TT spec allows blending of 87 and 91/93; presumably if those grades are TT then the mix could be too. If you find a station that's TT in all grades...

There sounds like more of a price spread in 93 than 87. My compromise would be a few gallons of TT 87 then fill up with cheap 93.

 

[sciphi]

I'd shop on price, then add my own additives like MMO to keep one element constant. The Mobil station is a few cents more than other stations, and offers a free cup of coffee with a 10-gallon purchase. So it's worthwhile to fill up there when I want coffee.

 

[Audi Junkie]

The engine is running great on Hess 93 and TT 89 mix, ECU is set on 91 octane. The problem is I can't even floor it until 3rd gear without spinning the 225 tires. 300ft-lbs from a 4-cyl.