i have a 96 wrx with typical mods(exhaust,hks air kit)i get about 260-290 miles per tank mind you ive seen snails with zimmer frames pass me at times lol most ive ever had was 306miles just above the red line

 

I got 62 miles for 17 litres (£22) the other day in a 160bhp Hawkeye Sport. Thats 16mpg, I was stuck in traffic a lot and crawling everywhere. On the motorway Ive seen 400 miles without the orange light coming on. It depends on your driving environment.

 

I'm glad I got rid of the M5, I put £35 in and I managed 60 miles!! I only drove around town usually staying in 4th as it was very torquey low down! Think it had a 70litre tank and I managed 230miles on that!

My old 475/460 MY05 STi could manage 300 miles on it's 60litre tank was much happier with that!! So glad I'm back in a Scoob, none of the 5.0 V8 thirst rubbish!!

 

Did the op ever get this looked at? I get around 75-80 miles to £30 currently... 2003 STI PPP.