Real Gasoline, not Ethanol

We would need to know why Toyota recommends 95 in OZ, but conceivably better detergents or other formulation factors. Each country will have unique gasoline pool characteristics reflecting typical refinery configuration and whatever local "EPA" regulations they have. Sounds like Toyota does not like what is in lower grades in OZ, which could include higher sulfur, manganese or whatever etc.

As one expert recently said, and I always try to say, many of detailed analytical properties of gasoline are "invisible" to the consumer, so we would need some insider info to know what is going on in OZ (and what is going into the tank).

 

Mmm, some conflation afoot there?

The Owner's Manual spec's regular gas, stick with that recommendation? The Prius' "higher" compression ratio has been explained here before: it was too much for my brain cells, but bottom line was the engine will not have the gas requirements of a traditional high compression engine.

 

The compressions ratio is about 9.5 to 1*, the expansion ratio is 13 to 1. Otto Cycle engines do not have two different ratios, but Atkinson Cycle engines do.

* the timing of intake valve closure can be adjusted, so there is no hard 'compression' ratio, but It can't be adjusted to 13 to 1

 

Ok, well 9.5:1 is certainly not a high compression ratio.

 

The Prius has a theoretical 13:1 compression ratio, but it's actual ratio is much lower than this "about 8.5:1" because the inlet valves are kept open at the beginning of the compression stroke pushing air and fuel back into the inlet manifold. This means compression does not start at bottom dead centre. This is the reason it's called an Atkinson cycle engine. An engine with a shorter compression stroke than it's combustion stroke.

John.

 

I've meant to follow up and look into the finer points (I usually find Phil Irving gives a pretty good explanation), thanks.

That still leaves the mystery of why Aus Prius manual recommends 95 or higher. I appreciate the point wjtracy makes about additives but it still seems pretty senseless putting a higher octane fuel in such a low compression unit.

 

I know nothing about Australian laws and regulations so let me explain the US.

Prior to 1995, the oil companies could add as many or as few detergent additives to gas as they wanted. Higher Octane gas tended to have more additives, so the companies could advertise how much better the higher octane grades were for your cars. (They make more profit if you use higher grades)

In 1995 the EPA mandated a minimum amount of detergent additives. As a result, the oil companies reduced all detergents to the minimum, even for the higher octane grades. By 2004 the auto manufacturers started a Top Tier Gasoline Program. Top Tier requires a larger additive package for all grades.

So in America, all grades now have the same amount of detergent, either the EPA's limit, or the Top Tier limits for 61 oil companies.

I do not know if Australia is like pre 1995, pre 2004, or the current US situation.

I assume Toyota does know.

 

That's a pretty fair bet, I agree.

 

I love E0 gasoline in my Washington state, & burned it, when E0 could be purchased within a dime of E10. Even used E0, when it cost 15% or 16% more than E10. Two or three years ago with gov't interference, the E0/E10 price gap surged to 30% difference, even at my favorite E0 station. Less than a year ago, one E0 station, some distance from me, began selling E0 at 16% more than E10. I purchased their E0 & even got happy when their price dropped to 12% above E10 prices. Now tho, E10 prices have dropped greatly & the E0/E10 prices are again approaching 30% difference, even at my favorite E0 station. Its just nuts!!!

 

The Australian 2008 owner's manual specs 95RON or higher.

 

I read an test analysis of the results of burning 3 different Top Tier gasoline brands (unspecified brand names), and the results showed that the detergent packages were differentially effective in reducing carbon accumulations in the combustion chanber, on the one hand, and on the valves on the other hand. The authors also explained that adding more additives to reduce combustion chamber carbon accumulation could also result in increased carbon accumulation on the valves, so the additive packages are a curious and delicate balancing act. If the specific brand and grade information were made public with that type of detailed test results, we could all use, say, a boroscope to check carbon accumulations on our valves and combustion chambers, and then pick precisely the brand and grade that would help our ICEs last the longest.
(Not that I’m OCD or anything.)

 

What's the lowest octane at Australian gas stations? I'm thinking either:

1. There's a lower octane regular at Oz stations.
2. Octane numbers are in a different scale (apples/oranges).

 

Minimum ethanol-free grade is 91RON which I think is roughly equivalent to 87MON. Aus fuel has to meet stated octane rating at minimum. RON is RON, there’s no fiddling it.

From owner’s manual:

Fuel Type
Research Octane Number 91 or higher. For improved vehicle performance, the use of premium unleaded gasoline with a Research Octane Number of 95 or higher is recommended.​

 

I believe Oz maintenance schedule also calls for periodic fuel filter replacement? (Toyota USA and Canada do not.)

Maybe fuel supplies are "dodgier"? I'm stumped.

 

Wow, in Australia if the average car could get more than 50,000km without a filter change that person was real lucky, I'm talking a bout the large volume fuel injected vehicle filters here. I owned my automotive workshop for 12 yrs and replaced fuel filters every 10,000kms and they always showed near mud when shaken and then drained out in reverse to the normal flow direction. My Prius has probably the highest mileage of any on this forum at 724,000km on the clock now, it was an ex taxi and the fuel filter was changed the same time as the oil and oil filter and I believe this regular servicing is what has given it such a long life.
As far as the ethanol debate effecting engine life, 724,000km says it doesn't shorten the engine life so that's enough testing for me to make a positive assumption that the effects of ethanol on engine life is nothing but scuttlebutt put out by vested interests.
All of my petrol fuelled vehicle run better on E10 and all have hi mileage on the clock. A '74 VW Kombi ( no idea what they are called in the US but a poptop camper panelvan) has 850,000km plus on the clock, 300,000km of that I put on and have used nothing but E10 and LPG. These air cooled twin carburetted engines were designed to run on high lead fuel, the old standard grade and it was roughly 89 octane or euroRON (research octane number) and Australian E10 is 94 octane.
A '95 model Ford 4.0 ltr fuel injected 6 cyl with approx. 800,000km on the clock, the ex taxi '08 Prius with 720,000km and now a PHEV '06 Prius with 262,000 km on the clock.
Non ethanol standard fuel in Australia is now advertised as being 91 octane but in reality can be as low as 89 octane because it is something that is not regularly "policed" in Australia where E10 is scrutinised by every one with a barrow to push, so you do get what they say you'll get or better.
I think a lot of the confusion comes about with the difference of euro Ron number and the US (Ron + Mon)/2, Euro Ron95 = US91, thus the Australian Prius recommendation of RON95 by the manufacturer.

T1 Terry

 

You’re contradicting yourself there, Terry.

 

Gasoline supplies in the USA have been very, very clean for decades. Not true in most of the rest of the world.

 

Here at Finland we have 95E10 and 98E5 RON fuels. Wikipedia tells that in europe fuel is measured at RON and in usa its average of RON/MON. MON is usually 8-10 units lower value that RON, So 98RON is equal of 88-90MON.
Seems that EU 98 is something like USA 94 then.

I always use 98E5. Why? I might be old school but i dont want more ethanol.
Also fuel mixture is leaner with higher octane fuel, that may help keep exhaust parts/EGR cleaner? That is question what i would like to know. I read that engine needs to make richer mixture to make same ammount of power with lower octane fuel. That is also reason why MPG is better with higher octane fuel.
But difference is still so small that maybe it does not have anything to do with for example blocking EGR cooler sooner when using lower octane than higher.

 

Thanks for that, I've fixed my error now, think I need a proof reader :lol:

 

Sorry about referring to this old post, but:
Yes, totally agree with you. On other websites, there have been people stating they had emissions tests, which were performed with the vehicle burning 100% ethanol-free gasoline (E0). Not only did the vehicle pass emissions tests, but the drivers were complimented for their vehicles having exceptionally fine emissions tests.