The detergent packages are the same in each gas grade. There was a big FTC ruling back in the 70’s that prevents companies from advertising that higher octane gas is superior to regular in cars that don’t need it, which includes saying that the premium gas has better detergents. (I suppose they could technically still do it, but they couldn’t advertise it so what’d be the point?)
I think he meant Top Tier, not premium.
Oh, right, oops :smack:
Not close enough to make it worth the drive.
I guess you mean for those whose cars are designed to run on 87.
I have heard that there are places where you can find 100 octain fuel. It’s used for highly tuned track/race cars. It would be interesting to see how my AMG would run on a tank of that.
By I’m digressing. I guess my question about Top Tier Gas is more or less answered. Most national brand gas retailers add detergents to their fuel to help combat engine deposits. Hard to really judge which formula/additive is best. And “best” would be marginal anyway. I think I’ll just continue to alternate from brand to brand as a matter of convenience, etc.
I read you can get 100 at US race tracks, funnily enough the two standard options in most of europe are 95 and 98 octane. I don’t think it’s even possible to get a gas with a lower octane level, although there also seem to be some different ways of measuring. Maybe that’s the difference.
Octane is measured differently in Europe. In the US, quoted octane levels are measured as (R+M)/2): an average of RON (which is the measurement used in Europe) and MON (a knock measurement taken at higher engine speed than RON). So 93 octane fuel in the US would be approximately equivalent to 98 octane in Europe.
It would run exactly the same as it would on 91. Again, there is no benefit to running higher-than-recommended octane gas.
Octane measures how resistant fuel is to spontaneous combustion from being compressed in the cylinders, also known as “knocking.” If the fuel/air mixture goes “boom” in the combustion chamber before the spark plug sparks, that causes a knocking sound and causes the engine to be out-of-sync. This is more of a problem in high-compression (usually for performance) engines.
Knocking was not good for older engines without knock sensors, newer engines with knock sensors and computers can adjust the timing/mixture/whatever to compensate. You might get less power or efficiency. My car requires 91 octane but there is no 91 octane at any nearby gas station, just 87, 89, and 93. I routinely run 89 without issue. I occasionally run a tank of 93 and don’t notice any difference.
also be careful because race gas is still allowed to contain lead.
Quicksilver, I don’t think your AMG would run any better on 100 octane.
Maybe I’ve been misunderstanding, but I think the common perception of octane is backwards. “Octane” isn’t a performance enhancer. It doesn’t make gas burn better, or quicker, or more completely. Instead it actually retards combustion.
Engines are prone to “pre-ignition” – the heat from compression of the fuel/air mix can trigger combustion before the spark plug fires, indeed before the piston reaches the top of its travel. The resulting knock or “ping” can damage the engine. So additives are used to retard combustion, preventing “ping”. The ability of a gasoline to resist pre-ignition is displayed as its “octane rating”. Higher octane = greater resistance to pre-ignition.
The tendency to pre-ignite is in large measure determined by the compression ratio of the cylinder. Higher compression ratios are more prone to “ping” and require higher octane ratings to prevent it. As it happens, higher compression ratios also are often used in high performance engines. Hence the actual link between high octane and high performance.
But the manufacturer’s recommendation is the final word in this silly marketing game of “up-sell the octane rating”. No vehicle has any use for an octane rating any higher than the manufacturer recommends. No use at all.
I don’t know what this says about Top Tier gas, but the confusion over octane is distracting me.
Probably fairly poorly.
The octane rating says how much you can compress the gas before it spontaneously goes boom, and that’s all it says. It says nothing about quality or energy density or much of anything else for that matter. Ethanol’s octane rating for example is well over 100 (something like 115 or so, I think, but that’s from memory and I could be wrong). But the energy density of ethanol is horrible compared to gasoline (roughly 2/3 the energy for the same volume).
The higher octane fuel you use, the higher compression ratio you can use in your engine, and a higher compression ratio will extract more energy per volume of fuel and will turn less of that energy into waste heat.
If the fuel has a lower energy density, your AMG engine, with its lower compression ratio, can’t take advantage of the higher octane to extract more energy from the fuel, and therefore runs worse on the higher octane than it would on a lower octane that the engine is more closely tuned to. A lot of the higher octane fuels also have a slower burn rate when used at lower compression ratios, which will further reduce the performance of your AMG’s engine as it throws off the engine timing.
So there’s a good chance your AMG’s overall performance on 100 octane won’t be so good.
If you feel like going through the hassle, mixing equal proportions of 89 and 93 will get you 91.
Which, by the way, is how gas pumps do it.
Gas stations usually have one tank of the lowest octane and one tank of the highest octane. Any in-between grades that they offer are a mix of the two.
Got it. Not going to mess with 100 octane. Thanks for your responses, all. 
The Master has spoken … “What’s the difference between premium and regular gas?”
Yes, but that’s not the question.
Strange, the idea that the additives get added at the station came from earlier threads on this topic from people in the business.
Very odd.
If you live in an area that has been flagged by the EPA for air-quality issues (as we have here in Chicago), you may not be able to find it at all. Ethanol gets blended into gasoline in many urban areas in order to cut down on emissions that contribute to smog.
Also, if you live in a state that’s a big corn producer, you may also find that ethanol gets mandated in your state in order to make corn farmers happy.
I understand completely.
I once knew some moron who had bored out his 240Z’s engine and modified it to the point where even the best 93 wasn’t good enough fuel for it anymore.
He bragged that he had an “in” at a local airport that would fill his tank and as many gas cans as he could fit in his hatch-back sports car with real “jet fuel” for $200 cash.
While I can’t say with certainty, I’m pretty sure that eventually he blew up his engine.
For me, the knowledge that I am running the highest detergent package available is worth the small performance hit I get with the 89 octane. The engine compensates and the higher octane only really benefits during high acceleration. If I am going on road trip in my BMW (great road trip car, btw), where I’ll be cruising at 70-80+ for hours on end and know I won’t be doing much, if any, stop-and-go driving, I’ll run a tank of 87 octane, topping off with the highest octane I can find when I get to my destination (and expect to have to stop and start a lot). I do make sure that it is Exxon, Mobil, Texaco, etc…, that is a Top Tier distributor. Keeping the engine, particularly the intake side, is important on high-performance engines.
Any engine work on the V12 gets expensive, quick. There are 12 injectors, 12 sparkplugs, two distributors, and so on. Oil changes are always on schedule (usually a bit early) with only Mobil 1 Euro blend. Do you run synthetic oil in your AMG?