Accord VTI 2.4 - should I use Premium Unleaded?

[pmptrading]

Hello!
Are there any benefits for me using PREMIUM UNLEADED? I have the Thai built Accord VTI 2.4 ..... it says it only needs standard unleaded....

Should I treat the car to Premium?

Is there much performance gain?

Is it better for the engine?

WILL IT MAKE THE ENGINE LIFE LONGER? Hoping to get 20+ years from this car.... HOPEFULLY THEN IT WILL BE PAID OFF!!! LOL

[aaronng]

You get benefit if you use 98 RON because those fuels usually incorporate additional detergents. The 95 RONs might have less than the 98.

You shouldn't find any performance gain since the ECU doesn't compensate for higher octane.

[EuroDude]

:eek: I thought the K24A4 used Premium like the Euro's K24A3.

Anyway yeah dont waste ur money on 98RON, its too far a jump from the engines tuned rating of 91RON. Unless you want to take advantage of 98RON's cleaning additives to clean the engine once in a while, as aaron said.

[panda[cRx]]

standard unleaded is fine. if you want use premium every 4-5th time.

in all your threads you keep stressing about getting 20 years out of the car, this is not hard to do in a honda so you can relax a lil :)

[EuroDude]

I would imagine Premium would help a lot though if you want to extend the engines life that much, 92RON is quite dirty.

Since 95RON burns more efficiently, it may work out to be the same price per tank.

[aaronng]

:eek: I thought the K24A2 used Premium like the Euro's K24A3.

Anyway yeah dont waste ur money on 98RON, its too far a jump from the engines tuned rating of 92RON. Unless you want to take advantage of 98RON's cleaning additives to clean the engine once in a while, as aaron said.
His car has the K24A4.

[aaronng]

I would imagine Premium would help a lot though if you want to extend the engines life that much, 92RON is quite dirty.

Since 95RON burns more efficiently, it may work out to be the same price per tank.

95 RON doesn't burn more efficiently than 91 RON.

If I wanted to use premium instead of regular, I'd go for 98 instead of 95 because there are more "advertised" detergents in it.

[EuroDude]

ur confusing me aaron :p

High octane fuel burns 'sooner', therefore the engine uses less fuel for the same amount of power. So you can say that the fuel burns more efficiently due to less fuel wastage.

[aaronng]

ur confusing me aaron :p

High octane fuel burns 'sooner', therefore the engine uses less fuel for the same amount of power. So you can say that the fuel burns more efficiently due to less fuel wastage.

High octane doesn't burn sooner. High octane means that it is more resistant to self/auto-ignition. That is the meaning of the octane rating.

[JohnL]

ur confusing me aaron :p

High octane fuel burns 'sooner', therefore the engine uses less fuel for the same amount of power. So you can say that the fuel burns more efficiently due to less fuel wastage.

The 'heavy' hydrocarbons that make up the bulk of the chemicals in petrol contains more energy per CC of volume than do the 'light' factors mixed into the fuel to act mostly as octane enhancers (these are typically chemicals such as benzine, xylene, toluene etc, and they exist in very substantial quantity in unleaded fuel). The higher the octane rating the more of these octane enhancing chemicals are in the brew, displacing heavy hydrocarbons that have more energy per CC. This means a typical commercial high octane pump fuel will have less energy per CC of volume (lesser calorific value) than lower octane fuel.

Such a higher octane fuel used in an engine that doesn't require the higher octane (mostly but not necessarily only due to a lower compression ratio) will produce less power and worse fuel economy than the engine would using a lower octane fuel. The difference may not be great, but in theory it exists, and can be significant, at least I've read reports of it being so (I haven't personally done any back to back fuel economy etc testing of high and low octane fuels in low compression engines, life's too short!).

Here's where people get confused; An engine that requires a higher octane fuel (because of higher compression, or more accurately higher compressive cylinder pressure) will develop more power and have better economy than an otherwise similar engine with lower compression running on lower octane fuel. If you use high octane fuel in a low compression motor then you have inefficency from the lower CR, as well as a lesser calorific fuel, so you lose on two counts.

The reason for this apparent paradox is to do with the compression ratio itself, i.e. higher CR promotes a more complete and efficient fuel burn than does a lower CR, and it's this that gives improved power and economy in a higher compression engine, despite the fuel being used having a lesser calorific value.

Using high octane fuel when not required is counter-productive to both power and economy, the only reason as already suggested might be the possible inclusion of larger quantities of detergent agents in the higher octane fuel that theoretically ought to keep components such as injectors and piston rings cleaner in the longer term.

Whether these fuels actually do contain higher quantities of these agents is not really something we can know for sure. From what I can gather some of the major oil companies in the USA have been forced to amend their advertising of high octane fuels when they couldn't prove the beneficial cleaning affects they were claiming....

One of the products that is known to be a worthwhile cleaning agent in fuel (to the best of my knowledge) is known commercially as 'Techron', and this is used in Caltex fuels in some provable amount (it's a Castrol, or rather a Texaco product). It's not a lot as I understand it, but at least it's in there and is known to work, just how well in the quantity that Castrol uses I don't know. This is also the main active agent on some proprietary injector cleaner products, such as Castol's own one (can't recall what they call it), and the Nulon injector cleaner, maybe others. There are most probably other good cleaning agents I don't know about.

In an engine that doesn't require a high octane fuel, using a lower octane fuel along with using a good chemical injector cleaner a few times a year may be a better bet than habitually using a more expensive, less economical and calory deprived high octane fuel. The additional cost of the high octane brew must add up to quite a bit over a year, or the life of the car, and it won't be beneficial if you're car doesn't require it (IMO).

[Gio]

Agreed^^^

What about that new 'green fuel' stuff. I have noticed that i get about 50 km more from using it. Is that type of fuel bad?

[JohnL]

Agreed^^^

What about that new 'green fuel' stuff. I have noticed that i get about 50 km more from using it. Is that type of fuel bad?

I know nothing about this fuel, what's in it, or it's octane. Up here in the sticks (near Taree) a lot of the servos haven't had any high octane at all until relatively recently (and some still mightn't), which was a bit of a pain with my last car that hated low octane (Cressida, vey nice car for what it was, but had a top shelf drinking problem!). My current car (CB7) doesn't need high octane fuel, so I don't keep up with what's available.

If the 'green stuff' has a lot of ethanol I'd tend to avoid it, but if it's giving you good economy then it might not be a bad fuel. You need to be careful with percieved economy, the only way to really know the difference between different fuels (i.e. avoid the placebo affect) is to keep very careful checks on economy, and 'km per tank' isn't a good measure, too many variables. You really need to brim fill and keep careful track of k's and litres between refills (to the brim of course).

[Gio]

yeah i think its ethanol fuel, is it bad for the engine?

[JohnL]

Not bad no, in that it won't damage the engine. But in theory it can be bad for the fuel system because the ethanol is hygroscopic , i.e. it absorbs water and over a long time any water that gets absorbed into the fuel can potentially oxidise the alloy components in the fuel system. (Don't ask me why hygroscopic is spelt with a 'G' and not a 'D', haven't a clue!)

In any case it's only a real problem in higher concentrations than you'll find in pump fuel (10% ethanol is supposed to be the max allowable). My main objection is that alcohol isn't petrol, and has a lower calorific value so a petrol / ethanol mix can cause a decrease in power and fuel economy compared to 'real' petrol.

[EuroDude]

High octane doesn't burn sooner. High octane means that it is more resistant to self/auto-ignition. That is the meaning of the octane rating.

Yeah thought so, I was reflecting the comments made by a honda mechanic on another forum, guess he's not such a great mech afterall :p

@JohnL, thanks for the detailed info :thumbsup:


So if your engine is designed for 95RON, will you get better fuel economy if you use 98RON?

[JohnL]

So if your engine is designed for 95RON, will you get better fuel economy if you use 98RON?

A lot of people seem to think so, but my understanding is no, all else being equal.

[e240]

Actually, I used some E10 fuel or something from a private servo, I thought it felt pretty good. If my car could take E10, I'd have no qualms using it all the time.

[Gio]

wow john u know ur fuels. wd mate :)

[aaronng]

Yeah thought so, I was reflecting the comments made by a honda mechanic on another forum, guess he's not such a great mech afterall :p

@JohnL, thanks for the detailed info :thumbsup:


So if your engine is designed for 95RON, will you get better fuel economy if you use 98RON?
No, you won't get better fuel economy because it's 98RON. If you do get fuel economy, it's probably from the different additives or the claimed "higher fuel density" of the aussie 98 RON.

[JohnL]

wow john u know ur fuels. wd mate :)

Not really, fuel chemistry is hugely complicated, I probably only know 'enough to be dangerous'! In the scheme of things I'm a rank amatuer in my knowledge fuel chemistry.

[JohnL]

Actually, I used some E10 fuel or something from a private servo, I thought it felt pretty good. If my car could take E10, I'd have no qualms using it all the time.

Any difference in economy between commonly available fuel adulterated with alcohol or not is only going to be relatively slight (I'm sure the oil companies don't want anyone actually noticing a significant difference with alcohol laced product). To actually know how much of a difference there may be you'd have to do careful back to back economy testing. The same goes for your arse dyno, hard to feel the difference.

I think we also need to keep in mind that alcohol isn't a panacea for fuel shortage problems. The environmental benefits aren't as clear cut as some might have us believe, and if the world goes to very large scale alcohol fuel production this is at the inevitable expense of land that will be available for food production, creating substantial food shortages in some areas of the world and and hikes in the cost of food for the rest of us lucky enough to still be able to afford it.

[JohnL]

No, you won't get better fuel economy because it's 98RON. If you do get fuel economy, it's probably from the different additives or the claimed "higher fuel density" of the aussie 98 RON.

Call me cynical, but claims like "higher fuel density" are somewhat suspicious to me. What exactly is it supposed to mean? Is it a term used by the fuel chemists, or by the marketing department? Does the legal department have to construct a carefully qualified legal argument / justification before they sign off on the use of such a term in promotional material?

My understanding is that the 'heavy' hydrocarbons are known to be denser factors than at least the majority of the additive 'light' factors, and it's known that the higher the octane the less 'heavy' and the more 'light' factors are present in the fuel. If this understanding is correct, then how can a typical higher octane pump fuel have a "higher fuel density" than a lower octane?

[Gio]

E10 is the 'green' fuel right? I think thats what i use.

[aaronng]

My understanding is that the 'heavy' hydrocarbons are known to be denser factors than at least the majority of the additive 'light' factors, and it's known that the higher the octane the less 'heavy' and the more 'light' factors are present in the fuel. If this understanding is correct, then how can a typical higher octane pump fuel have a "higher fuel density" than a lower octane?
That's because octane rating is not linearly related to density of that component. You can use a higher proportion of high molecular weight hydrocarbons and then compensate with an additive that has a higher octane rating to offset the decrease.

Actually, the heavy alkene and aromatic components that you are referring to have a higher octane rating than the lighter alkene components. Of course, there are also lighter components with low energy value and even higher octane ratings like ethanol (116 RON), toluene (114 RON) and MTBE (117-121 RON).

[aaronng]

E10 is the 'green' fuel right? I think thats what i use.

10% of it is green. Also, how green is green? It still takes a lot of energy to distill ethanol. Even if the energy comes from the burning of cane husk, that still generates CO2, which contributes to the big issue of global warming.

[JohnL]

That's because octane rating is not linearly related to density of that component. You can use a higher proportion of high molecular weight hydrocarbons and then compensate with an additive that has a higher octane rating to offset the decrease.

Actually, the heavy alkene and aromatic components that you are referring to have a higher octane rating than the lighter alkene components. Of course, there are also lighter components with low energy value and even higher octane ratings like ethanol (116 RON), toluene (114 RON) and MTBE (117-121 RON).
I think I should be more careful not to confuse density with volatility, which is what I suspect 'lighter' and 'heavier' refers to, i.e. 'lighter' being the more volatile aromatics, the stuff that goes 'pffff' when you open the tank cap, and escapes leaving a lower octane fuel behind!