premium petrol vs ulp regular

Uppy,
I believe it has something to do with the RON Level Premium Has a higher RON than Regular I think its 98RON so it burns a lot cleaner. I usually try to put a Full tank of Premium in every 5 tanks or so (When the Price Is Right) to clean the injectors out, I know there’s a lot of I thinks here but I think its right! Someone a little smarter than me will be able to correct I’m sure

HTH

Keep It On The Rough Stuff

Matt (W.A.)

The main thing is that if you vehicle has what they call a "knock sensor" it will allow the computer to advance the ignition timing a bit more which allows a more efficient burning process if you are using a higher octane rated fuel.

So you are probably right it's not just the "halo effect"

The improvement in fuel consumption running on PULP is marginal in the Subie, but the motor seems to run smoother and pull a little better. The problem is that the improvement in consumption doesn't cancel out the increase in the price - usually up to 6c/L dearer.
Some of the new 'high tech' motors will only run on PULP so their owners will be unable to do trips 'outback' to places where PULP is unavailable.Subaru Forester
"size isn't everything"

BP Ultimtate 98' is 98 Ron
Caltex/Ampol Premium 96' Ron
Other brands can only guaratnee 94' Ron in premium
Std ULP 91 RON

On my little 250cc 4Cyl Quad Carbi 4 Stroke Bike it will not start on ULP, it will not start on premium in cold weather, BP 98 it runs like a dream! (it is a jap import so it is used to running 100 RON fuel).

Also get 25% better economy and smoother idling out of 98 verses std premium.

RON is a measure of Octane rating. Octane does not refer to power or energy in the fuel. It refers to the ability of a fuel to be compressed without combusting. If you run a high compression car with low octane fuel the fuel will combust before the spark creating hotspots and knocking. The reason you will get better fuel economy out of premium is because it has a higher DENSITY. Shell optimax is 10% more dense than regualr unleaded so it contains more energy which is released on combustion giving more power. For example if you put in 100 litres of regualr you will get say 80kg's of fuel where as 100litres of optimax will weigh 88kgs. So the optimax will give you more power per combustion thus requiring less fuel to be burnt to provide the same power as regular unleaded.
Hope this helps,
Cheers,
Justin

Hello all
My forester is fuel sensitive, unlike the rangie which uses so much in comparison that it stays at home until we need hard core 4x4.
The Prado we took to Darwin didn't care what we put in, ie no difference felt.

Paying extra for premium for the Foresteris balanced by the improvement in fuel economy.
As the car is built to run on a range of fuels, the computer adapts vis the knock sensors etc to suit the different octane ratings.
On Optimax i get up to 50k more per tank and smooth running.

On safeway normal ulp I get noticeable engine hesitations and reduced economy
On shell normal ulp I get occasional hesitations.
Refilling with high octane shell or BP fixes it within 100k.

Caltex high octane same effect as optimax.
Mobil is very variable sometimes as good as optimax sometimes causes hesitations.
BP high octane gives very slightly less economy but more grunt. I run BP when I want to give it a cleanup.

The high octane stuff also varies depending on how long it has been stored in that it doesn't seem to like long exposure to heat etc. The car always seems to run better on fresh stuff.

Anyway thats about 150,00 K's of my experience. Confusing ain't it

regards

A

Thanks guys that anwers my question .Ill keep putting the good stuff

I am glad to see you got home safe... and i hope you took a photos of the landcruiser moment in the sand.????...
Glad to hear you like the window shields or whatever they are called....
Talk to you soon.....___________________________________
Simpson trip 05/04 then turn left at Birdsville to Darwin via Lawn Hill etc
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