95 vs 98 Fuels

[bmorris]

Hi all.

Just a comment for those out there who are using 98 oct fuel in their cars. I have a 06 BF XR6 four speed and have always used 98 fuels for as long as I have had the car. Recently I've switched to using 95 and have found my fuel economy has actually improved (I was expecting the opposite). I have noticed that the power seems to have decreased but only slightly and hardly noticable (but I expected as much).

Anyway I was surprised at the result and it could be food for thought for those like me finding it hard to justify the extra cost of 98 fuel.

Maybe someone who knows more about the science could explain why I'm getting these results.

[IceValk85]

98 octane fuel is often boosted by ethanol.

as we all know ethanol burns faster, hence a possible reason for your decreased mileage, due to more ethanol being in the fuel (could be anywhere between 1 and 10%)

pure ethanols some neat stuff, somewhere near 120 oct. great race fuel when used appropriately.

Ice

[Jim Goose]

Umm.. unless you buy fuel containing "ethanol" .. like it says on the pump, there shouldnt be blending of fuels otherwise in standard fuel.

[SSD-85]

Owning an assumingly stock-tune NA XR6 makes having anything above 91RON hard to justify....

Just my worthless 2c...

[Gricey]

there pretty much exactly the same, except for a slight increase of Octane for the 98, but myself I cant feel any difference in performance between them, so i stick to the 95. www.designedtoclean.com.au/Vortex-Difference

[mik]

Originally Posted by bmorris

Hi all.

Just a comment for those out there who are using 98 oct fuel in their cars. I have a 06 BF XR6 four speed and have always used 98 fuels for as long as I have had the car. Recently I've switched to using 95 and have found my fuel economy has actually improved (I was expecting the opposite). I have noticed that the power seems to have decreased but only slightly and hardly noticable (but I expected as much).

Anyway I was surprised at the result and it could be food for thought for those like me finding it hard to justify the extra cost of 98 fuel.

Maybe someone who knows more about the science could explain why I'm getting these results.

this is how fuel was explained to me as a young buk, generally low octane fuel burns quickly and so is more suited to low/medium compression engines, having higher cylinder pressures(high compression) can cause the low octane fuel to detonate in an uncontrolled fashion rather than burn quickly, detonation can cause premature wear and damage to engines,
some cars have engine management that can adjust the spark timing to compensate for the lower quality fuel with a bit less power,
higher octane unleaded burns slower and can take advantage of advanced ignition timing giving slightly more power, every engine is different, head designs are different, fuel quality at servo`s imo can be slightly different, so you need to see what runs best.
ethenol mix is a different kettle of fish and needs an engine tune or engine management to take advantage of it`s properties, my AU does`nt like the stuff and pings it`s guts out on the local stuff, if i have any of that wrong happy to be corrected, but i think it`s it`s close to the mark though.

[bmorris]

Originally Posted by Eagleheart

Owning an assumingly stock-tune NA XR6 makes having anything above 91RON hard to justify....

Just my worthless 2c...

I notice a difference, it's only small but the extra km you get between 91 and 95 is worth it. I no longer think so between 98 and 95

[rancidpunx]

I can tell the difference between 95 and 98. The second time I filled my turbo ute up I put 95 in by mistake as I didn't realise at the time there were 2 types of Premium fuel. I believe there is a thread here that I started asking what was wrong with my car. When I filled up the following week I noticed my mistake and have stuck to 98 since.

[AU Mont]

my car goes slightly better & a couple more km's to the tank on 98 compared to 91, but i save a crapload of money putting 91 in the tank compared to 98.

common sense really.

[xisled]

IMO you are wasting your money going on 95 or 98 in a XR6. They are made from factory to run on 91. This will probally be the best for your car.

If your car is tuned for 95 or 98 then you should use that type of fuel.

I have found it more of a mental thing, you put 98 in and you think you have more power, etc.

[AWD Chaser]

My opionion of fuels:

[Rodge]

Recent NA inline six's are rated at 195 kw's and three hundred and ninety something nm's, (someone on here will remember the exact nm rating) and will run fine on 91 Octane but makes 198 Kw's and 409 nm's on 95 Octane so with the extra power and torque it can be worth running them on 95, but as you suggest you're probably throwing money away on 98.

OTOH with forced induction engines (especially turbo six's) I've noticed a considerable power and torque difference over the years running on 98 Octane.

[mik]

Originally Posted by xisled

IMO you are wasting your money going on 95 or 98 in a XR6. They are made from factory to run on 91. This will probally be the best for your car.

If your car is tuned for 95 or 98 then you should use that type of fuel.

I have found it more of a mental thing, you put 98 in and you think you have more power, etc.

mmm i dunno , while that might be the case it does`nt always work out that way, i think in some area`s fuel qaulity varies, best to do the suck it and see approach, try a tank if it does`nt ping you should be ok.

[LeadFoot81]

We have two WS Fiesta Zetecs in our 'fleet' (a 1.4 auto and a 1.6 manual) and both get better mileage on V power 98 than on 95.

I worked it out and the extra kilometres per tank outweigh the extra cost.

I haven't bothered trying 91 as my wife's previous Fiesta hated the stuff.

[Jack960]

On average it'd cost roughly $10 more to fill up with 98, given the power gains (I didnt buy a 4L falcon for economy), I am happy to pay the extra. I found slightly more response and better economy on 98, only a fraction better economy.

[Polyal]

As above, cars are made to run on 91...your doing no disservice to yourself if your not chasing every 0.1kw.

In saying that id I had a turbo id run it on 95

[Coyote mk3]

I use 98 and notice a difference over 95

I notice a difference in how the car runs between shell, caltex and bp 98
BP I find the car runs much smoother and gets more ks to a tank when compared to shell 98.
It might just be an old n/a 6 but I like to put in what i feel it runs best on.

[xisled]

If you have a look at the current prices and what it cost to fill a 68 liter tank.

So if you are looking at the the price difference with 91 to 98. It is just over $10. You know need to work out if it cost you more or less to fill up using 98.

These are taken from BP in Carlton Vic

BP AA Carlton 98
price: 152.9c
Price to fill up$103.97

BP AA Carlton 95
price: 146.9c
Price to fill up.$99.90

BP AA Carlton 91
price: 137.9c
Price to fill up. $93.73

[GT69]

Originally Posted by Coyote mk3

I use 98 and notice a difference over 95

I notice a difference in how the car runs between shell, caltex and bp 98
BP I find the car runs much smoother and gets more ks to a tank when compared to shell 98.
It might just be an old n/a 6 but I like to put in what i feel it runs best on.

I've noticed this as well, Always try to use BP if I can. The power difference in the turbo between caltex or shell 98 and BP is very noticeable.

[Franco Cozzo]

Got a choice of 91 or 98 at my local servo, 98 for the Fiesta, Diesel for the Focus.

[Silver Ghia]

Advantages using 95 or 98 octane is dependent on the particular engine design.

I found no advantage using 98 or 95 octane fuel over 91 octane in my BA I6, however there is a distinct improvement in the FG I6 NA.

The specified 195kW power and 391 Nm torque figures are obtained using 91 octane fuels. Due to the FG I6 4.0 NA engine configuration, these figures are increased to 198 kW and 409 Nm for 95 octane fuel with improved efficiency, and further again when 98 octane fuel is used.

Ref: http://www.autoweb.com.au/cms/A_1100...wsarticle.html

[Itsme]

Originally Posted by xisled

IMO you are wasting your money going on 95 or 98 in a XR6. They are made from factory to run on 91. This will probally be the best for your car.

If your car is tuned for 95 or 98 then you should use that type of fuel.

I have found it more of a mental thing, you put 98 in and you think you have more power, etc.

What vintage XR6 are you referring to?

You obviously do not drive a late model such as an FG XR6 to make that comment!!!

I will use 95 or 98 over 91 any day regardless of price and if the truth is to be known I get better economy/value with premium fuels than using 91.

[Drizz06]

Never tried 95 but have always been able to notice a difference from 91 to BP ultimate 98 in all my late model cars. FG has been tuned for 98 but ran much better before tune with continual use. Wife's focus has a bigger difference and runs so much better on the good stuff that even she noticed it. I only rarely buy 91 when im no where near a BP.

[xisled]

Originally Posted by trublu

What vintage XR6 are you referring to?

You obviously do not drive a late model such as an FG XR6 to make that comment!!!

I will use 95 or 98 over 91 any day regardless of price and if the truth is to be known I get better economy/value with premium fuels than using 91.

No I don't drive a late model xr6. I wouldn't bother with a 6 at all. But that's my opinion. My GT always gets 98. It been a few years since I owned a car that could run on 91.

Maybe it is because my daily is a V8, that the difference is minimal and I wouldn't notice it. but end of the day IMO unless your car is tuned for anything more than 91 using 95 or 98 will not make a a big difference.

[distantbullz]

I notice slight better mileage and slight performance with the BF I like to look at the instant fuel consumption to see how much I use, 91 uses on average 10-40L/km for light acceleration, 95 about the same 10-35L/km while compared to 98 get 10-30L/km with same/similar driving style 95 and 98 price difference I see are roughly 5c or less when at the pumps so usually go with 98

[DFB FGXR6]

From BF onwards, the standard I6 was able to adjust the PCM to suit 91-98ron fuels. So 91ron is fine, but if you choose hight octane fuels, the PCM will adjust to suit. Hence power/economy gains on premium fuel.

[335POWER]

I personally find the 95 to be better in both economy and power than the 98 but that's just me

[2011G6E]

95 or 98 octane?

Any "improvement" one way or the other will be purely psychological...you won't notice that small a difference in a street engine with the wide tolerances they have. I would wager the fuel you normally buy varies more than 3 octane one way or the other depending on how old it is and how good the tanks are storing it.

[Coyote mk3]

I'm sure a better average fuel economy is not psychological.

[XR6T0Y]

Used to use 95 in mine, got about 515 k's per tank.
Use 98 now, get over 600 per tank.
Power? No idea, can't remember how it used to be. Economy? Hell of a lot better