ETOH is ethanol.

 

I disagree with the argument that 93 is cleaner gas. Studies have shown that cars that run on 87 actually perform worst with 93 octane gas. In both milage and the amount of polution produced. So please, somebody counter this arguement with some FACTS.

 

I haven't seen any such studies, but I don't doubt it at all. I know retarding your ignition timing will make emissions worse and high octane fuel basically has a slower propagating flame front. That's good for making it resistant to detonation but if the engine is only designed for 87 octane in the first place, it won't be advancing the timing enough to take advantage of 91/93 octane's properties anyway. Hence, it would be like driving with the ignition timing retarded.

 

Brandon is pretty much right. While there is no significant energy difference in the different octane ratings of gasoline, it does effect the chemistry of the combustion process. The higher octane gasoline breaks down into precursors to combustion that tend to have a slower reaction rate. It therefore has less of a tendency to knock which causes the spark to be retarded by the engine control system. The problem is that if your car is designed to run on 87 octane, the control system will not advance the timing to benefit from the 93+ octane, and thus you're spending your money and getting no benefit.

 

We're not talking about the combustion or energy or FE properties of premium vs 87. That's been beat to death over and over and over in many threads, and there is no debate over it.

The question at hand with respect to toptier fuel is the value of detergency. It DOES exist in all gasolines to some degree, per EPA regs. SOME retailers DO put MORE of it in their higher grade fuels. It IS preferred by at least GM, Toyota, and the other TT originators, and it WILL help celan out a gunked engine. Ethanol is often the primary detergent, but there are other additives in use.

The real motives behind the creation of the "toptier" standard are a little cloudy, but seem to be rooted in the car makers' desire to ensure a more standardized national fuel supply with enough detergents to all but ensure that their warrantee costs from emissions repairs will zero out. The EPA hasn't responded to this desire, and the fuel makers are reluctant in the face of variable regulatory environments and pure intertia. So the car makers are trying to work through the retail marketers' associations (SIGMA, et al). Its a new project, and not much tracking or data is available about it.

One thing is clear- they are definitely using the detergent angle as a marketing angle to differentiate product, and hoping that this hook of swaying consumers will influence the fuel comapnies to bring their gas to the preferred level. Better or not for the average driver? Probably not, but its a marketing hook that exists.

The original question in this thread is only whether it is worth seeking out toptier fuel stations and/or using certain vendors' premium fuels for their additional detergency; not for any FE or performance change. This given that the OP is starting with a new, clean engine, using modern fuel, and intends to keep it for a very very long time (>10 years?).

My vote is no; it is not worth it to always pay any extra or go out of the way for TT or premium fuels just becasue of their detergent additives. The engine is clean now; under normal conditions it will take years for deposits to form to the levels that GM, Toyota, etc are concerned about. The detergent levels desired by GM, etc in the toptier standard are set to be so high as to be able to clean out a very fouled engine (read the test spec on the toptier site).

 

I just saw this thread this morning and until today had never heard of (or paid attention to) this Tier system for gasoline.

Well, I changed the oil in the '05 and while I was under the hood I happened to read the Emisssion Control Information sticker (had to do something while the oil bottle drained). Anyway, the sticker says the vehicle is Certified to CA emissions standard something-or-other and SULEV AT PZEV or whatever WHEN TESTED USING TIER 2 gasoline. Guess Tier 2 is good enough for the emissions standards to be me, no sense chasing Top Tier stuff.

I didn't look under the hood of the '06 but I would assume it to be the same.

 

Tier 2 = low sulphur, EPA designation
Toptier = high detergency, marketing designation

tier 1 and tier 2 were/are EPA emissions standards, generally related to the LEV/ULEV/SULEV bin categories. All cars sold outside the clean states (CA, MA, NY) met tier 1 emissions standards through 2003.

2004+ cars (and light on-road trucks/vans/SUVs) are subject to tier 2 standards, comparable but a little more relaxed than CA's SULEV regs. But to do that, low-sulphur fuel is required nationwide...hence "tier 2" gasoline is being phased in (2004-2006) to get the vehicles to meet the requirement. The car will run fine on "old" fuel but is certified to meet the EPA category listed on the car with new "tier 2" fuel.

If you go to the green vehicle guide, there are 2 categories- old and new. Tier 1 and tier 2 scores. http://www.epa.gov/greenvehicles/about.htm

So "tier 2" low-sulphur gas is called that because it is part of the "tier 2" emissions regulations.

Now...
"Toptier" gas is a marketing name for a gasoline standard that GM, Toyota, Honda, and Toyota would LIKE to see implemented, but are going at it from a marketing, rather than regulatory, slant (how very capitalist of them). Although related to emissions in that its supposed to keep the fuel system/engine cleaner, its mostly about preventing/reducing deposits to reduce their repair costs.

And to reiterate, none of this has anything specifically to do with FE, MPG, energy content, or any other differences between fuels.

 

Actually, the detergent level does effect fuel economy. As I stated in an earlier post, the higher levels of detergent are supposed to keep the injectors and throttle body cleaner, which helps the fuel flow patten and efficiency. The reduction of deposits on the valves and plugs affects how the engine control system retards the spark advance, which also effects fuel economy. Granted the benefits of detergents are not realized immediately, but they will be realized over several years. It still all boils down to where you want your money to go (the oil companies for gasoline or the auto companies for repairs/maintenance) and if you are concerned about emissions.

 

While I admit I don't no much about additives, it appears to me given the choice of FE verses cleaner jets, valves and combustion chambers, I choose to go with FE anyday. It all seems to me that getting poorer FE means losing performance also. Losing performance could not be helping the overall mechcanical conditions of bearings, pistons, rings and seals. We've taken out the lead and designed the engines to hold up much better without it, so why add detergents that may decrease FE in an aready clean engine.

With build-up of deposits, FE will start to suffer but additives over the parts counter are availible. They can be added with a smaller percentage of fuel limiting the long term effects of additives. If the valves are at a point of sticking, its time to go ahead and break the engine down for a valve job where combustion chambers, piston tops, throttle body and injectors can recieve the right cleaning anyway.

As far as the use of premium fuel in a vehicle designed to run on 87 octane, why spend the money? If a vehicle runs better on premium and gets better FE, its designed for premium and I would use premium. This issue turned me off about the Highlander Hybrid with using either octane. Is Toyota telling you to use premium for the additives to reduce warranty repairs or higher compression? Or both? From what I hear from some of the post, it may just be the additives if FE is not hurt with regular gas. The higher octane may just offset the poorer FE with the additives. Anyone?

If pure gasoline gives me the best FE, I can live without the additives and rely on pump and fuel system filters to keep the system clean.

GaryG

 

again, thanks to all for all the excellent information.

I think I will stick to 87 and go to the name brands (Shell, Chevron, and the sister companies).

Now my question would be ... if I wanted to add fuel cleaner to the tank to keep the injectors, throttle body, cylinder walls, etc to a 'like new' clean and for long term reliability (which would also keep up the performance and FE I would believe) ... What would some of you suggest? An additive every tank doesn't seem necessary but the $1 or 2 a tank is equivalent to buying a higher grade but adding the extra detergent myself and keeping the fuel recommended by the manufacturer OR one of the ultra powerful 'use only 3000 miles or more' detergents such as STP complete fuel system cleaner (silver bottle), Gunk, etc, pick the brand of your choice or suggest one (either for this one or the every tank one) .

I do want this car to last for at least 12-18 years, more if it is feasable. I plan on getting the next generation of IMA hybrids (in 2012?), but still keep the HCH I. If the HCH II is so much better than the HCH I, I am looking forward to a HCH III or a AH II/III. In fact, that is what made my decision to get the slightly used HCH I at a big discount, opposed to a new HCH II. In the test drive, I didn't consider it noisy, harsh, was quick enough, and had no problem getting great mileage in the city. I also have another 'project' in mind in a couple years once I part out my RX-7. I have some Insight-ful dreams