Can't see search facility, so here goes probably repeat question:

Beloved standard StiV, approx 28K miles, MPG recently gone down to about 23mpg (even cruising on M-way) - use to easily get 27 in same conditions, once even managed 30! (but doing steady 70 - boring/almost fell sleep). Acceleration is prety good and smooth, but then one gets use it as "normal" after a while. Also, the car had been stolen (no major damage) and set around for about 5 weeks while Insurance Co tried all their scams but failed (long story, posted last year).

I know spark plugs should be replaced about now, but could this be the only factor? Any feedback from your experiences much appreciated.

Cheers

 

Knackered lambda sensor always a likely suspect when symptoms like this present.

 

Defo Lambda.

My STi v had done 34k, very lumpy at lower revs, very poor fuel economy, changed the lambda, lumpy feeling gone and fuel economy has shot up big style.

A lambda's life is about 30,000 miles, but this is decreased with the use of OB.

 

Thanks Folks. The Lambda sensor was replaced about 10 months ago (22k) by main dealer, so I didn't suspect that. I will have it checked out.

Cheers