hotsaucePK

Just did my first full fill up the other day, and I've reset the tripdometer to do a little mini fuel economy test.
Since it was my first fill up that required Premium fueling (came from Honda), I had no idea which octane rating was premium (I am a complete noob with this...), and accidentally filled her up all the way with 89 octane (midrange).
LoL...
I realized this after I got home and doing some research.
It's not going to hurt my engine or anything (running it once is negligible), but people did comment that 89 will hurt the mileage..
So basically I've started a 89 vs 91 fuel economy comparison test... accidentally lol.
Keep in mind that I would always put 91 going forwards...

End of Day 2 currently (2 full day commute + 1 night of dating gf who has no car).
I would say it was 70% highway driving and 30% city driving, at worst.
Tripdometer is exactly at 120 km, and the full tank has gone down to 3/4 already!
Mathematically, that is 16L used for 120 km, which is equivalent of 13.3L/100km!!!
Even if I did 100% city driving, I'm supposed to get 11.4L/100km!!!
And I'm looking at maybe 500 km out of the full tank, if lucky!!!
That is waaaaay worse than what is norm on these cars (9.4L/100km combined, according to fueleconomy.gov).
This is only based on 120 km of driving and I would like to redo the calc after using the full tank, but still, this number is shocking and I hope it is solely due to 89 being in the tank as to 91 or better.

To the experts: can 89 hurt the mileage this much?

I'll report more near the end of this tank, and then do a comparison with full 91 filled up.

Slyman

I fill up my Kia Koup with 91 (premium) since 2 years now and I can tell you I do more mileage...and it's only a simple 2.4l motor, no turbo. And between you and me, we know the motor will be more clean after a while than with 89 fuel. Also, the throttle response is more sensitive with the 91-94.

With my TT, I put 94 inside when I can, if not, it's 91 nothing below that. And for your info, I do around 8L/100km and let me tell you, the gaz pedal is going on the floor a few times in each fill up !!

hotsaucePK

So the octane does make quiet a difference!
Good to know.
I would also like to run this tank and recalculate, some people have said that first quarter of that gauge goes down really fast compare to other sections, because of gravity etc.

8L/100km on TT is great!
Is TT 2.0T as well?

Daonhathai

Of course octane makes a difference in how your engine is tuned.

hotsaucePK

I knew it would make difference but just not by this much - but then again, I'd like to monitor the full 64L and see what I get exactly, and then compare with 91.

hotsaucePK

Hey all, just chiming back in with more driving under the belt:
I'm actually very surprised right now because the tank is still a bit above the half way mark (I'd say 30L used), and the tripdometer is showing 300 Km.
The gauge really does fall slower from 3/4 mark to 1/2 mark!
Keep in mind that I currently have the wrong fuel in there (89), so it is a bit pleasently surprising that I'm getting 10L/100Km.
I can definitely live with this consumption.

But like dennisA4 said, I can't rely on this calculation yet, I would like to use up the full tank first.
Anyways, I'm a happy man if I can get 600Km+ on a tank

Daonhathai

knock knock

Tim$2

Keep in mind that even one tank full is not a very good comparison measure. There are plenty of factors that can happen in the timeframe of one tank that will skew the result. You would need several tanks of 89 octane to determine if there was a true difference.

Slyman

Yes it is a 2.0T FSI and it is chipped on stage 1.

veriwide

It would be a good idea as well to do a fuel consumption test with the trip meter and actual litres used and then compare it with you readout. My readout is 10% low.. meaning when it says 9.0 it is actually 9.9.

BTW.. my first post here.

Bernard