Fuel Results... anyone got any explanations?

[bundabora]

Hi Guys,

I am not trying to start an argument about the best fuels or anything, but here are some things I have noticed. BTW - I have a 4 motion Bora with Sports Exhaust and K&N Filter - nothing else modded engine wise...

I used to use Shell 95RON because my closest servo sold it and they take Coles dockets I noticed my car hesitating a little under light acceleration even when it was warm - only when lightly accelerating. I spoke to my mechanic who is quite experienced and he said to try 98RON petrol and see if I notice any difference - he has a Turbo'd old Subaru - (a classic sleeper) and he reckons BP ultimate is the best...

So I get a full tank of the best BP stuff... first time I have ever paid $100 to fill my car. It doesn't hesitate any more but where I used to get around 10L/100 on my average fuel monitor thing with 95RON it rarely gets under 12 and often closer to 13L/100... why would that be?

After 2 full tanks and numerous checks for different trips, I tried Caltex Vortex 98 a week ago. Straight to 9-10L/100 and 8L/100 on the highway... and no hestation

Any ideas? Or similar situations?

Here's my Car... I have it lowered on Eibachs, Whiteline Swaybar - Rear, CAI, Sports exhaust, my controversial Subwoofers, a Double DIN Pioneer headunit, RS4 REP Wheels, Diesel Geek Sump guard, Angel Eyes Headlights and Depot Rear lights, debadged boot and Grille and Boser Bonnet in bare primer stage... not everyone's cup-of -tea, but my Son (15) and I like working together on it...

[Diesel_vert]

Fuel quality is likely to be uniform when it's fresh from the refinery.

However, quality is decidedly not uniform across service stations, and the rate at which it "deteriorates" depends on the fuel's age, fuel turnover, servo maintenance procedures and the state of its storage conditions.

That would mostly account for the difference in performance more than anything.

[leighaus]

also when your car is running better after being a slug for so long, you tend to have a heavier foot.

[team_v]

also when your car is running better after being a slug for so long, you tend to have a heavier foot.

That would be my explanation for it.
Then after a while you tend to ease off and that could have been what happened when the caltex fuel was used resulting in a lower useage.

[bundabora]

I can understand your suggestions - although my car hadn't been running badly, just the hesitations when lightly accelerating - so I was often lightly accelerating to see if the problem was better... I would often drive like a pansy, just trying everything to get it below the 10L/100 and I couldn't do it... the BP was bought from 2 separate servos too...

[Brisbane's Bora]

Not sure about the fuel, I have always used 98, as I was advised by about 10 people to use it.

On another note, your shaved trunk looks good (Y)

[kapowww]

I always thought since our cars are tuned for 95 that 98 would have no performance impact besides the cleaning properties...

[mikk]

that's a huge variance... more likely that driving style has changed it, but there could be something wrong with the car i suppose.

my 2.0 slow does better on ultimate than on bp premium. i worked that out manually over several months. ultimate was always more efficient. someone else on another forum with the same car as me did the same test (without me knowing) and when i saw his results the figures were exactly the same to a tenth of a litre. so for teh 2.0 slow at least i think ultimate is better.

[balkanac]

I've been using bp ultimate for the last 5 years that I have had the car and I'm constantly getting 12-12.5
as someone said, there might be something wrong with your car

[bundabora]

I get the same mileage as you on BP, but in the 10s with the Vortex 98... I can't see how there would be anything wrong with the car...

I am sure the driving style has not changed and the answer must lie in the fuel as this is my regular drive - I go to and from work 15km - every day, I work on the outskirts of the city - On the way home, I drive it pretty hard on the rural roads for the first 5kms of the trip home, then cruise along with the traffic the rest of the way - Today I got home and the average usage was 10.4Km/100 with the last 2 tanks of BP, I could never get it under 12 unless I cruised all the way and even then the best was 11.8. Cruising all the way with the Caltex yesterday, I got it down to 9.6 average...

I've been using bp ultimate for the last 5 years that I have had the car and I'm constantly getting 12-12.5
as someone said, there might be something wrong with your car