I got a 04 civic hybrid with 400800km a few weeks ago. Runs reliably. Of course had the Ima light and p1433 and p1600 codes and I hooked up grid charger.

I have two questions that bothers me.

1. When the car is idle or in auto stop, the fuel economy gauge goes to 12L/100km which is max
2. Climbing uphill on highway or anything over 3000 rpm ish also goes to max 12L.

First tank I got 7.8 then after grid charger is 7.2L. Definitely a bit higher than when the car is new I would imagine but where I live have up and down terrain. On the way back on highway is all the way down. Got the car to save some gas as I have a ml320 that uses 14L/100km and you have to put 91 in there.

Two other codes on the car is p0521 and p0420. The p0521 went away for a bit after oil change to mobil 1 0w20 synthetic and I added a bottle of cat cleaner.

I want to get the car down to 6L /100 I think it's capable. I think it may caused by the cat as well.. From my experience looks like the car is all original parts. Mileage is not too bad for this age of car here. Common here people drive 30000 to 40000km a year. Some cars 2015 already got over 200k on it.

Anybody put a straight pipe on this car before? Luckily in Canada we got rid of emission test a few years ago so you can do wherever you want with the cars.

The battery is from 2003. Grid charger definitely did something. I was off the P1433 and P1600 for a while. Haven't done a deep charge yet. The amount of fuel I saved is really not worth the money I paid for the RB batteries grid charger I could just use that on gas money. I don't think anyone should buy new batteries for this car anymore if you can buy one cheap.

On a good uphill highway I struggle to hit 110km/h and rpm is 4500 to 5000 and of course maximum mpg display.

Next step is remove the cat and try cleaning it or get the straight pipe which I don't think you can buy anywhere.

The oil pressure sensor code I think can ignore as it doesn't overheat at all even on a super hot fay with rpm over 5000. Still less than half on the temp display.

If I can get 100k km out of the car I would be happy.

 

Your mileage is terrible.

You're likely on the right track with the cat. P0420 doesn't just mean performance efficiency. It can also be due to obstruction. The gutless performance + P0420 strongly suggest clogged cat. There are cheap bolt-on cats out there, and if you were in the U.S., I'd tell you to seek out a local muffler shop to simply fabricate a straight pipe replacement. I've seen this done on two Prius, and aside from the continual P0420 and O2 sensor codes, there were no other issues.

6 is reasonable. 5.5 is probably do-able depending on the condition of the ICE. My '03 has 330km on it, and it readily hits 5.5. With optimal conditions - speed limit, mild weather, flat ground, no A/C, etc. - I can get down to 4.8.