Big difference in economy with different fuel

[anparkinson]

Ever since I got my 2007 2.0 litre Accord I keep a note of real economy (not the displayed economy) between fill ups at my local Sainsburys.

With a mixture of town, A road and motorway I always averaged out about 33mpg.

The last 2 fill ups I changed to Esso and the MPG has increased to about 36mpg.

I'll keep using the Esso but it looks good so far. I didn't realise fuel quality could make such a difference.

 

[Mr Honda]

Yes, it does make a huge difference, but my take on it is, that when you mix fuels (i.e. petrols from different companies), you get better results. I've switched a few times and each time after switching the fuel economy increased, but after then using the fuel a while, the economy tapered off again back to "norm".

In Ireland I've used Topaz, claims their fuel goes further, then switched to Esso, economy increased then tapered off, then switched to Texaco, economy increased again, then tapered off.

I've now just put 4 new tyres on the car (Bridgestone s001) and the economy is gone to utter ****e, not sure anything will make a difference now!!

 

[Mr Honda]

Oh, and it's a 2.0l petrol also.

 

[Goodluckmonkey]

The other thi got bear in mind is that you get different sized tank fills from different petrol stations - ie the pumps shut off at different times affecting the final tank volume.

I've kept track of my diesel for 11k now, and you always get an anomalous result when you swap over.

The diesel economy varies wildlydepending on fuel, but when I used to have a petrol accord (1.8 gen5), it was all pretty similar.
A petrol with a lower compression ratio will do similarly on most regular, but will drop economy if you put super in it.
Conversely, a high comp petrol designed to run on super will pull the timing and perform noticeably worse if you put regular in it.

My Subaru Legacy, which was designed for 100 octane in Japan, saw approx a 10% reduction in economy on regular, and would feel like it'd had its spuds chopped off.
It was one of the few cases I've seen where spending the extra few pence on v-power would yield enough of a result to work out cheaper than running on regular.