Top tier and tier 1 are generally considered one in the same, tier 1 as opposed to tier 2. It is still mostly marketing since the EPA standard is the supposed tier 2. The website you linked to is not an EPA site, it's a Top Tier promotional site. I will gladly be proven wrong, but I maintain that Top Tier (tier 1 or whatever) is an industry self standard not a government standard and therefore is suspect and can be inconsistent, as the OP claims.

People can knock the Top Tier/Tier 1 concept all they want. I learned about it here on the Green Hybrid boards, and we monitor every tank of gas. If I fill up at Shell (Tier 1) I get 35 mpg. If I fill up at Arco (discount) I get 28-30 MPG.

It's a no brainer. You can reset your MPG gauge and see the results in minutes... and those results stay consistant through the entire tank.

Oddly, there also seems a great deal of variation in Tier 1... and so far for me Shell has been the winner.

The thing you have to be wary of is a station selling gasoline that is supposed to be Tier 1 but is actually discount. We've gotten stuck with that a few times now... but if we go back to a reliable station we are right back to our 35 MPG.

I think the Shell additives must have more energy in them or something. I have monitored every tank from the time the car was new, and Shell outperforms almost everthing else to the extent that you can measure the difference even accross tank fill differences.

It is the ignorant among us that will eventually destroy us all.

Looks like I’m going to have to get medieval, like science 101 (burning the peanut). A peanut contains about 2.5 BTU of energy, that energy is the same regardless of where (country or state) the peanut comes from. Of course the salted, beer, honey roasted, and peanut brittle contain additives, but the basic peanut is what I’m talking about. In the world of gasoline and refining, the additives cannot change the amount of BTU that gas can produce. And my final, nothing to do with gas, How many times have you seen ads for skin moisturizers which read (penetrates the skin, soothing under the skin moisturizing etc…)… no matter what the marketing ads say, you will never find an over the counter moisturizer that penetrates the skin, because if it did it would be considered a drug (and need a prescription). How many of you are reading the moisturizer bottle right about now?? hahaha
I’ve never tried tier 1… but I will.

Lots of possibilities without actually changing BTUs. Better temperature stabilization, better mositure or water vapo(u)r removal, a way to improve vapo(u)rization out of the fuel injectors (rough analog to a wetting agent, but for fuel), etc.... lots of possibilities.

It is the ignorant among us that will eventually destroy us all.

True, actually way back when i was in high school, we would put moth balls in our gas tanks. The naptha would (supposedly) increase the volatility of the fuel and thus (our theory) would increase the explosive power at the pistons. Back then, testing was not on our agenda so we never knew if it actually made our cars faster.

I'm not too sure this is just an indusrty self standard. According to what I've read about Top Tier, it's a standard set up by car makers - BMW, General Motors, Honda, Toyota, Volkswagen and Audi - to assure their fuel injectors and combustion chambers stay clean to reduce customer complaints. I assume a gas company would submit test results to this ad hoc group to be certified as Top Tier and then it would be up to the gas company to follow through with compliance on an on-going basis. I'm not sure having it as a goverment standard would assure any better compliance - just look at the FDA or any goverment agency and how sopartic their checks can be.

Also looking around the internet I think the correct term is Top Tier - not sure where the Tier One terminology comes from but it sounds close.

As I stated before, there is not a single universal formulation used all the time all across the US. As for "additives", well, one "additive" (if you want it call it that) would be oxygenates such as ethanol, which has a lower energy content than pure gasoline. Since it's mixed in, that lowers the energy content of the fuel you receive out of your pump.

Example: Per http://www.energy.ca.gov/gasoline/ty..._gasoline.html "CARB Reformulated Gasoline (CARB RFG): An oxygenated reformulated gasoline which meets the most recent specifications set forth by the California Air Resources Board (CARB). This gasoline contains 5.7% ethanol as an oxygenate."

http://www.epa.gov/OMSWWW/rfgecon.htm shows the ranges of energy content for gasoline depending on the formulation for the season and also the energy content depending on the oxygenate.

06 Toyota Prius, 04 Nissan 350Z; mom has 07 NAH

Close, but unrelated. I don't think Tier 2 is related to Top Tier in any way except pehaps some level of co-marketing hype.

The Top Tier program was, as prevously stated, set up by a group of automakers with the objective of making a cleaner fuel from the perspective of engine life and engine performance.

Tier 2, from everything I have read, was completely different and setup by EPA to reduce polluting emmision from fuel, most specifically sulfur related emissions.

The two are not mutually exclusive -- or inclusive.

It is the ignorant among us that will eventually destroy us all.

That is the same thing we have found. Tier 1 in general is better... but Shell always wins hands down for best MPG. I have no idea why. I just know that in testing I get consistantly 35 MPG with fill ups from the Shell station... and crappy MPG with fill ups at other stations.

Somebody wrote a post a year or two ago about having spoken with someone at Shell who gave them the history of how Shell has tried to pioneer many aspects of improving gas quality and performance. I can't find the post... but it was very interesting.