98 octane fuel power/economy increase?

EA Bogan · 01-10-2007, 02:53 PM

I know engines are supposed to run better and more efficiently on 98 cotane but is the fact that its around 15 cents per litre more expensive than 91 worth it? interested in peoples opinons on the matter...

Tiapan · 01-10-2007, 03:12 PM

im not sure about an increase with my daily driver, but i can run my v8 on premium, and feel it a tad slower, put in some 98 and differant all together, runs much sweeter

Steffo · 01-10-2007, 03:18 PM

If you put 98 RON fuel into an engine tuned for 91 RON fuel it will use more petrol and make less power.

The oil companies want you to buy into the idea that it is "better," for your engine, but its sole purpose is to run in high compression or high boost pressure engines to stop detonation. All a higher octane rating means is a slower, more controlled burn.

mumbo.com.au · 01-10-2007, 03:31 PM

Quote:

Originally Posted by Steffo

If you put 98 RON fuel into an engine tuned for 91 RON fuel it will use more petrol and make less power.

The oil companies want you to buy into the idea that it is "better," for your engine, but its sole purpose is to run in high compression or high boost pressure engines to stop detonation. All a higher octane rating means is a slower, more controlled burn.

I'm no mechanic but I understood most modern cars had knock sensors and retard the timing if pre-detonation is experienced. Fuels with higher octane ratings reduce pre-detonation allowing a car's computers to advance timing thus generating more power per stroke and therfore better economy.

I saw an anecdotal story which had three "identical" Magnas running 91, 95 and 98 fuel. Bearing in mind they are designed to run on 91 octane fuel, the 95 RON achieved 20% better economy over the 91 RON on the same circuit with the same driver. The 98 RON fared about the same as the 95.

soulfire · 01-10-2007, 03:32 PM

Quote:

Originally Posted by Steffo

If you put 98 RON fuel into an engine tuned for 91 RON fuel it will use more petrol and make less power.

The oil companies want you to buy into the idea that it is "better," for your engine, but its sole purpose is to run in high compression or high boost pressure engines to stop detonation. All a higher octane rating means is a slower, more controlled burn.

True, but in a car with a self-learning/tuning ecu, if you run a car on 98 octane fuel for an extended period of time it should return better economy.

My XR8 gets better economy on 98 octane than it does on 95.

Taxman · 01-10-2007, 03:47 PM

I am a pen pusher and not a mechanic. However, visiting my clients I do a lot of km - 100,000 plus per year. I dispute the 15% dearer claim last night standard unleaded was 121.9 and 98 Optimax was 134.9 ie 10.6% dearer. I used to regularly run to the Riverina from Sydney (southern suburbs) every weekend 524km door to door. If I filled up on Optimax then according to the trip meter i still had around 170 - 180 km of driving to see clients when I got there. The only unleaded fuel I could buy in Lockhart in order to return to Sydney was standard unleaded, if I didn't top up on the way back, I would run out of fuel before I got home (only happened once than god for the NRMA at 2.00am)

My mechanic has also said that the 91 ron has a pink dye which over time leaves a varnish like deposit on the tip of the injectors and alters the spray pattern which affects the atomisation restricting the optimal burn. The 98 ron has no such dye and can assist in keeping the injector nozles clean giving a better spray pattern and enhancing the burn resulting in improved economy.

I find that each tank costs about an extra $7 - $8 but I get considerably more than $8 worth of additional milage compared to using standard unleaded

You may choose to either agree or disagree but this is what I have found from the last 10 years or so

cupic · 01-10-2007, 04:06 PM

My mechanic has also said that the 91 ron has a pink dye which over time leaves a varnish like deposit on the tip of the injectors and alters the spray pattern which affects the atomisation restricting the optimal burn. The 98 ron has no such dye and can assist in keeping the injector nozles clean giving a better spray pattern and enhancing the burn resulting in improved economy.

I like that Im using it from now on if the missus even thinks about rebuking me

cheers

STHSV8 · 01-10-2007, 10:35 PM

98 goes better

savagE · 01-10-2007, 11:26 PM

Its a lot smoother ride with 98 octane mate. I have an old poo-ey 4.1 crossflow carby and I have a noticable difference. Plus, there is less junk in it.

gz1 · 01-10-2007, 11:31 PM

I am sure the answer is it depends on the engine.
I did a test on my territory (see http://fordforums.com.au/showthread....538#post646538 ) and in my case over 3 tanks of fuel of each type there was no appreciable difference. The engine management system or whatever, should have re calibrated after three tanks, that is why I used that rather than a single tank of each.
Yet in theory it sounds like using a fuel with higher ron rating may allow you to use higher advance settings which in turn may produce more power which in turn may mean you actually use less throttle thus using less fuel.
In My opinion save the extra dollars by filling up with standard and put them towards a lottery ticket. Then you may get the winning numbers which in turn may allow you to buy a car that needs the premium petrol. Much better odds of that happening,

PoMmYwOG · 02-10-2007, 02:27 PM

I find 95 best for my car, i ran 98 for ages and it used more than it did on 95,i tried 91 for a while and definetly think 95 is better...91 i did about 50km's less to a tank...

Sam_Boss260 · 02-10-2007, 02:29 PM

Ok, I might start trying the 95 again. I tried this some time ago for a few tanks and did not find any difference.

So two questions. Does it matter which brand of 95? ie Shell, BP, etc

And for people who have gained in mileage have custom tunes?

PoMmYwOG · 02-10-2007, 02:47 PM

i recommend the BP 95 octane...i did use shell for a while, but wasnt as good... i noticed a difference when i put the bp back in again...vortex isnt as good either...

steve.zissou · 02-10-2007, 02:49 PM

I have a Lexus Ls400 and also drive a BFII Ghia v8 often and in both cases I try to use the cheaper ethanol fuel available from united servise stations in sydney. It is 95 ron and I can feel the difference (in the LS400 4ltr v8 it is very noticable). I notice no difference between this and 98 ron (ie optimax). So I get the benifits of premium for 2 cents a litre less than regular 91 ron.

as to economy - the lexus gets about 5-7% better fuel economy and the v8 ghia maybe 2-3% although I find the ghia hard to drive exconomically - mainly due to my right foot).

as to the evils of ethanol - I have been using for a couple of years now on and off and I have to say i see no evidence of fouling in filters or injectors when I took them out..

Road Games · 02-10-2007, 02:49 PM

Quote:

Originally Posted by Sam_XR6

Ok, I might start trying the 95 again. I tried this some time ago for a few tanks and did not find any difference.

So two questions. Does it matter which brand of 95? ie Shell, BP, etc

And for people who have gained in mileage have custom tunes?

Ahem .....If i may Sam ? BP Ultimate makes THE most Hp & Torque on the Dyno with a custom tune . Others have dribbled crap in here about no appreciable difference blah blah , it works Ive proved it , Jason uses it , WE run the numbers - my consumption is around 11.4l /100kms mixed driving and the plugs pull up as new....... On a side note , filled the van up at the Mobil that night , with 9000 I think ?It was premium anyway - the van loved it !! Wont touch Shell petrol BUT i use their oil .....Cheers .

Bossxr8 · 02-10-2007, 03:27 PM

I read a test done on a BA XT a few months ago and the best economy and performance was achieved on 95 octane. 98 didn't make any extra difference over what the 95 achieved over the 91. If you go too high in octane with an engine that isn't tuned for it you won't gain anything due to the slower burn.

Sam_Boss260 · 02-10-2007, 03:43 PM

Quote:

Originally Posted by DAZZLER351

Ahem .....If i may Sam ? BP Ultimate makes THE most Hp & Torque on the Dyno with a custom tune . Others have dribbled crap in here about no appreciable difference blah blah , it works Ive proved it , Jason uses it , WE run the numbers - my consumption is around 11.4l /100kms mixed driving and the plugs pull up as new....... On a side note , filled the van up at the Mobil that night , with 9000 I think ?It was premium anyway - the van loved it !! Wont touch Shell petrol BUT i use their oil .....Cheers .

Ok, so am I right in saying that with a tune, go the BP Ultimate (it's 98 isn't it?)

And for no tune, try the 95?

By the way, love your avatar picture and the location !!!

Road Games · 02-10-2007, 04:00 PM

Yeah yeah ,found it last night on the forum somewhere? jessica alba ?? And yeah , always ran ultimate anyway . Wife doesn,t agree ,because she cant use a shoppa-docket, but i know when she has filled it up with crap because it pings around 3000rpm ............... I use Octane booster at the track too , on tune 3 ...

Tote · 02-10-2007, 05:52 PM

My Mum has an ED 4.0 fairmont and she achieves around 20% better highway economy when running 95 octane Vs 91. I have tried both in my BA company Falcon and found very little difference in economy or power.
Regards,
Tote

ThoR_ · 02-10-2007, 06:01 PM

I have a AU S2 200kw. Standard pretty much and i run Premium usually because its a big more friendly on the pocket but when fuel goes down i run 98.......Ultimate sucks!!!!!!!!! Its a lotto draw for crying out loud. The octance ratings are never what they say they are and 98 is usually never 98.....91 is somewhere in the 80`s 95 is pretty much 91 and 98 is 95. (BP Servos)

Ive used Ultimate before and found no difference AT ALL and then every now and then it would make a big difference. So i gave Vortex 98 a whirl and everytime it has worked for me and made a huge difference. My car runs smooth and silk on it, more power, less noise and everything.

I also have 'Nulon Pro Strength Octane Booster' in my boot and when every i fill up i put 70-80mls in just to help it out.

So thats my 2c worth

cupic · 02-10-2007, 06:27 PM

Seen the latest ep on fifth gear and they did testing on booster additive(Wynns SPT etc) and the such and found on the power side that they all lost 2% power on 1/2 throttle and up to 6% on full throttle

cheers

redranga · 02-10-2007, 09:33 PM

Ive tried premium fuels in all of the cars that ive owned. The only one that it made a difference to was a 1978 Celica that used to knock under full load.

In my au2 and a corolla theyve made no difference at all to the economy or the power.

In both these cars I ran premium while going back and forth from Nsw and kept a note in my diary.

It may be worth running these fuels through to give the fuel system a clean once in a while but I wouldnt use them all the time unless youve got mega compression or force fed.

Have a read of this site:
http://www.fuelsaving.info/index.htm

Its full of info about what works and what doesnt