Now there's a stereotypical thread title

But... I'm serious. I just filled up my '96 STI and worked out I got 28mpg out of the last tank, most of which was a 70mph cruise to and from Rallyday. On my previous tank I got 24.

So, should I be:

a) thankful that I can spend the saving on beer, or
b) paranoid that my pistons are going to melt and big ends disintegrate because the MAF is knackered?

 

a) driving at a steady 70 uses very little fuel. I get 24 around town and sometimes as high as 30 on a long run. Only 6 on track.

 

Id be chuffed mate. My car allways averages between 22 and 24 for my general driving to work etc but on a run ive had 32mpg before. Sat at about 70mph following slow family members. However i did have a buggered MAF once and had to get the car home from Newquay. It worked out at nearly 40mpg which was a bit scary. I was told that at 60mph it would be ok anyway so m pretty sure i didnt damage the old girl.

 

why does a knackered maf give better economy i replaced mine not long ago but cars drinking fuel very heavily (160 a tank) and exhaust is black and was told it was maf or o2 sensor,im confused

 

If it under-reads, the ECU thinks that the engine is sucking in less air than it actually is. So, it injects less fuel, which means better economy but also higher temperatures which can melt the pistons.

Conversely, if it over-reads, the ECU thinks the engine is getting more air than it actually is, so it injects too much fuel - hence the poor economy and black, sooty exhaust.

 

when i wash my car,my exhaust is always black/sooty...what do you guys recommend??