AUIII I6: fuel consumption up by 10-20%

[rowan194]

I have an AUIII Fairmont I6. My fuel consumption has gone up from the mid-high 13's, to 15's (sometimes 16's) in the past couple of months. At first I thought it was a bad batch of petrol, because it happened suddenly, but I've mixed up the outlets since and there's no real change.

No unusual friction or rubbing noises. No change in engine note. No pulling to one side. No hard auto changes. Oil is clean (has been changed routinely once since). Basically nothing is jumping out apart from the trip computer showing higher consumption.

I did have a minor misfire due to deteriorated leads, I replaced them and also the coil pack, but no change.

There is one possible thing, I replaced the sparks a little before this started happening (maybe a month?). I checked them a few days ago and they look good... not like the "bad" examples in the gregory's manual.

The engine is stock, apart from a tickford snorkel. What else might be causing the high consumption? I've read that resetting your ECU can be a bit hit and miss - mine has been reset twice since, no diff.

Time for a compression test? Thanks for any help.

edit: will first hook up an LED to the diag connector to see if it's flagging any faults, that would probably be a good place to start...