[Jens VS]

I recently bought my 2001 Focus Wagon and the seller stated he got about 7-8l/100km. I figured that might be low but was a bit surprised to only get 9.5 (~24.5MPG)

I switched the plugs and cables that were quite old and it got worse at 11. So I rechecked the gap (which I hadn't done) and gapped them only to see it go up to 13 (17MPG). So I brought it to my mechanic who confirmed they were the correct plugs but found the PCB valve broken that they replaced. No change to mileage.

I then worried that I had broken the plugs when gapping, so I picked up and installed a new set and it dropped to 10.5, high, but a lot better than anything after I tossed the old crappy plugs. After a day of driving at -15 in the snow banks, it dropped the 12 and has been hovering around 11.5 ( 20.5) ever since.

I used the NKG plugs and cables that were recommended by Lordco, no check engine light and my mechanic didn't find any other issue than the PCV valve and I did explicitly complain about the terrible mileage.

Any recommendation or thoughts? I bought this vehicle only in September and specifically didn't buy an SUV to save on gas! But right now, it used just as much as my old Outback and RAV4.

I should say that I drive like a grandma, most trips are around 30km and it's been around 5C recently. I also had all fluids replaced.

 

[Jens VS]

I replaced the air filter when I did the plugs the first time, didn't think anything could have gone wrong but I'll just take it out and install again.

The mechanic also OK'd the smoked intake and cleaned the mass air flow filter. How would I find out if the cat is plugged?

The thing that baffles me most (beside the overall low fuel economy), is that it got worse after driving in the snow and stayed that way.

 

[Jens VS]

I'll do some youtubing for how to access this part. My idle is a bit rough but pretty low, so it's a different sound.