Super unleaded seems to give LESS power!

So with almost 1200 miles per month, I am piling the miles on the old Z. The thing I am finding though is that standard unleaded is giving more power than premium super unleaded. It's mainly noticeable at very high revs - 5500-7000, where with the standard unleaded there's a definite extra "push", but with the super unleaded, it feels much flatter.

Mine's a 2.5SI with sports exhaust and I think a mild re-map. General performance is excellent but high octane fuel does not seem to give any benefit. Anyone else experience the same thing?
 
Could also be old fuel. Super isnt as popular as normal unleaded so it can sit a while in a tank (although super unleaded usually is better resistant against aging, so its the preferred fuel to use in motorbikes and gas lawnmowers that can sit a while)
 
I only use super so can't say normal fuel is better performance wise. I doubt it is but I don't know all the science behind it. I know it's better lubrication wise and better for my engine.
7000rpm on the other hand is not so good for my engine and no use to me either really as all the torque has gone by then and the BHP is tailing off.

Just a thought.
 
noiseboy72 said:
So with almost 1200 miles per month, I am piling the miles on the old Z. The thing I am finding though is that standard unleaded is giving more power than premium super unleaded. It's mainly noticeable at very high revs - 5500-7000, where with the standard unleaded there's a definite extra "push", but with the super unleaded, it feels much flatter.

Mine's a 2.5SI with sports exhaust and I think a mild re-map. General performance is excellent but high octane fuel does not seem to give any benefit. Anyone else experience the same thing?
I think your just getting used to the car,it's reached it's limits for you. Time to get a 3.0is you will feel the difference again then.
Just my pennies worth.
D
 
Z4 COUPSTER said:
noiseboy72 said:
So with almost 1200 miles per month, I am piling the miles on the old Z. The thing I am finding though is that standard unleaded is giving more power than premium super unleaded. It's mainly noticeable at very high revs - 5500-7000, where with the standard unleaded there's a definite extra "push", but with the super unleaded, it feels much flatter.

Mine's a 2.5SI with sports exhaust and I think a mild re-map. General performance is excellent but high octane fuel does not seem to give any benefit. Anyone else experience the same thing?
I think your just getting used to the car,it's reached it's limits for you. Time to get a 3.0is you will feel the difference again then.
Just my pennies worth.
D
Forgot to add as above you are passing the limits of the torque curve,after 5500 on our engines it's dropping off .
 
Every independent test I've seen seem to suggest it makes absolutely no difference at all with 'normal' cars like ours. Just a marketing tool to extract more money from keen drivers.
 
Not to change the subject but - "mapped for what fuel" is what I'm noticing here in Europe. I have US spec Zed 3.0i and it is mapped for low octane fuel. The highest we had was 91 now 93 is more common in the USA. I get the lowest octane fuel that I can find in Europe which seems to be 95 and my mileage went way up per tank.

I averaged 275 miles per tank on 93 octane in the US and just on my recent highway trip here in Europe, I averaged 350 miles and the trip computer indicated 98 miles left on the tank.
 
AngryZed said:
Not to change the subject but - "mapped for what fuel" is what I'm noticing here in Europe. I have US spec Zed 3.0i and it is mapped for low octane fuel. The highest we had was 91 now 93 is more common in the USA. I get the lowest octane fuel that I can find in Europe which seems to be 95 and my mileage went way up per tank.

I averaged 275 miles per tank on 93 octane in the US and just on my recent highway trip here in Europe, I averaged 350 miles and the trip computer indicated 98 miles left on the tank.
Are you comparing like with like through, as Eur RON is worked out differently to US RON.

95 RON (EU) = about 91 RON (US).
 
"95 RON (EU) = about 91 RON (US)."

Excellent point on RON but, I still don't get why my mileage went up ?

I have been told this before but never believed did until I experienced it myself. The performance on EU lowest grade gas is excellent, I don't see any difference in performance and the dealer told me that the compression ratio between US variant vs EU is different do to the type of gas we have in US. The dealer actually called it "US has dirty gas vs EU".
 
I think the car is using less fuel on super unleaded, as the crackles and pops definitely decrease. Doing a red line 2nd to 3rd gear change will normally give a good pop and bang, but on super this is missing and the power increase above 5k is smoother and not as pronounced.

I think I will stick to standard fuel for the time being. Thanks for the replies
 
Back
Top Bottom