Fuel octane

Our fuel formulations may be different but we worked out in a previous thread (here) that I'm using the equivalent of 86 octane (with no Ethanol). I don't have any issues.

 

8,000 miles. No issues at all with regular fuel and octane.

Have use premium for a couple of tanks. Nothing was better because of it. Won't run it again.

 

Ethanol may be cheaper, but it gets less mpgs. There is less energy contained in a gallon of 10% ethanol than in a gallon of plain gasoline. 3% less is the usual concensus.

 

As far as I'm concerned, they have failed to make a convincing case where I live and I see inconsistancies in the arguments made. The 3% worse fuel consumption figure is also touted by our local motoring organisation and the government, which is inclusive of the fact that E10 fuel here supposedly has a higher octane rating than our regular unleaded, although technically it is not required to and information on this topic varies very wildly depending on where it is coming from. It does appear that the standard of E10 sold by different companies here is inconsistent.

As it happens, at the lowest price that I've purchased fuel since getting the c, the price saving for E10 would have been 3.06%. Going forward, excise levels are being increased on Ethanol which will reduce the % saving on E10 fuel here. So I certainly have no financial incentive to use it.

Surprise surprise the one group who is unreservedly supportive of E10 (and makes claims such as "performance levels in fuel consumption between the two fuels were minimal", "you are getting high octane fuel at a discounted price") is the primary supplier of Ethanol in Australia. On the other hand, several organisations claim that E10 does not produce lower emmissions per kilometre, only per litre.

So - the case for E10 has not been made satisfactorily to my mind and I have no financial incentive to use it. I have a choice here (although it's started to be restricted and I can now only get Ethanol-free regular unleaded at certain fuel stations). I choose to use regular unleaded without Ethanol. I'll review if the situation changes.

 

... AFAIK except for some kind of mechanical problem, you should be fine with Regular 87 R+M/2 for all Prii.
This includes as age accumulates on your vehicle. Believe a few (2010/2011) Prii may have had a knocking problem but that was a mechanical fix and not a fundamental Prius requirement for higher octane.

 

There is no shortage of info on the subject for those that seek it.

 

Octane & Ethanol are 2 different things and perform 2 different tasks, higher octane is normally used in high compression motors that usually cause pre-ignition and the "Pinging" noise like a bad timing. Higher octane lower the point where the explosion arise (like timing) to avoid this knock noise. Modern motors has advanced electronic that compensate for that without doing any mechanical adjustment. If a specific car recommend a certain level of Octane, it's because it's been programmed or adjusted for that specific octane. Often, they recommend octane 87 or better where the advanced electronic will compensate to reach the optimal point of ignition. Under the recommended 87 octane, chances are very good that it will "Ping" and can even damage the motor. Ethanol is completely an other story and as far I'm concerned is a total BS. Ethanol rise very little the octane ratio but lower the performance in combustion, that means it change the ignition point a little and lower the given energy vs gas only (loss of power) . Ethanol leaves residu in the combustion chamber, pistons, rings and is not as clean as ethanol free. Now, for us to choose which is better, i'd say stick with what is recomended in the book and maybe once in while, fill-up with some super ethanol free for 1 or 2 tanks to clean that ethanol mess.

 

OP, where are you located?

It would be nice to update your location info.

 

EPA unfort does not conduct MPG testing with ethanol/no-ethanol so there is no good way to know exact vehicle response to E10+ unless in the future Consumer Reports, EPA or someone pays to do such testing.

 

For almost anything you want to know about gasoline, check out Chevron's Motor Gasolines Technical Review. This is a very comprehensive summary of the science of gasoline. Specific to this thread, octane is covered starting on page 6, fuel economy starting on page 9 and the question of E10 vs. ethanol free is on page 12, paragraph 2.

With regards to the OPs original question, I have not had any pinging/knocking. I recently drove I-40 across the Appalachians and the uphill sections were a heavy load. No knocking. For that matter, I have not noticed knocking with any cars built in the last decade.


Tom

 

Many years ago, I ran comparative, hill-climb tests using different gasolines and grades with our 1.5L, NHW11:


There were small but detectable difference in groups of gasolines, not all brands were equal in the Huntsville market. This was pre-E10 days (or at least postings on the pumps.) But I also ran both Shell and Texaco 93 octane gas and found at maximum power, the engine would 'tune' to use the higher octane.

At no time could I hear 'knock' during these tests suggesting the knock sensor works quickly and effectively. Also, the effect was evident ONLY at maximum power ranges, no advantage at slower speeds. In fact, the higher octane fuel was in the pack of lower performing brands.

Bob Wilson

 

Bob- Nice data. Suspect those fuels were in the days when we had 10% ethanol+MTBE in reformulated gasoline, if your area was using reformulated gasoline. Also in those days sulfur levels in gasoline may have been higher. Sulfur does not directly impact MPG, but to make ultra low sulfur gaso for today, there may have been some other changes in the fuels you tested.

 

Oh man, do I remember the occasional stinkin' car trailing a cloud of sulfated exhaust . . .

Huntsville has a lot engineers for NASA and US Army so we tend to be a little particular about fuels and stuff. I was always amazed to find driving 50 miles out of town, there were the "may have up to 10% ethanol" stickers but nothing or very rare in the city. Then a couple of years ago, some busy-body work-up and now we're in the same E10 mess.

It was bad enough not having any way to assay the samples other than burning them. Now with variable amounts of ethanol, I just don't bother to do any more testing. But it was curious to see the brand differences and the octane effect in the hill climb.

Bob Wilson

 

...thank you. incredibly detailed Motor Gasoline review from Chevron. In one place they stated gasoline with higher energy content (due to composition factors) may show up to 1% percent better miles/gallon MPG. However, it is not practical for the consumer to know the energy content when purchased, so generally you cannot control this. In general, premium octane grades may sometimes contain a little more energy content, but the small extra MPG boost is not worth the extra cost. There was also much discussion (as expected from Chevron) about the need to keep engine deposits under control, but there was no suggestion that ethanol causes more deposits/sludge. This should probably be a "sticky" reference somewhere, not that I am in total agreement with it, but good starting point.

 

Here is nice articles to read from top to bottom (Ethanol in your gas) and it reflect many many others I've red so far !

Ethanol in your gas.pdf - Google Drive

And an other one on Octane and E10 Ethanol

Gasoline Octane and E10 Ethanol Blend Fuels