My truck does around 20l/100km with a manual 4.2l. Air filter is new, new spark plugs and wires, cleaned MAF with CRC sensor kleen, ran lucas injector cleaner. It runs well, has guts, but god it loves gas. I was thinking maybe the O2 sensors but I dont have any error codes? What should I be looking into?

 

I would not think that the O2 sensors are bad especially if you are not throwing codes. However, perhaps your engine is running cold or the engine temperature sensor is bad. A cold engine uses a lot more gas. This could be from a stuck open thermostat, low temp thermostat (should be using 190 degree), cold weather driving, or a sensor that is giving you a bad reading.

Im thinking that since you mention km's, you are from Canada and do a lot of cold weather driving.

 

It was the same this summer. I would get 14l/100km last winter. Temp does get to normal operating range fast enough. I dont know what to check :-(

 

I would think that your truck would get to normal operating temperature after about 8 Klicks in the winter when it is real cold. If it is not, perhaps your thermostat is stuck open. Before we assume that, it your coolant dirty? have you changed it withing the past three years? did you buy the truck used? and you don't know the maintenance performed? Would be best to have a little more info before we just assume it is the thermostat and change something that is not broke. If yes to any of these (and no to "did you change the coolant") I would feel safe in telling you to change the thermostat.

You should use a 195 degree thermostat in your truck for the engine to run most efficiently and get the best fuel economy.

 

I never changed the coolant. Engine gets to operating temperature fast enough (about a 1/3 up the gauge including full gauge range). Changed spark plugs, wires, air and fuel cleaner. Ran seafoam some 20000km ago.

Its hard to start whatever temperature (always been) and guzzles gas (not always been) but since I have no code I dont know where to look). On top of that winters cold as hell and never seems to give up a little so I cant do much.

 

I noticed on my truck that it wasn't getting quite as warm as it use to, it was still warm but not as warm as it once was. My mileage dropped so I went and changed my thermostat. I get up to temp like I use to and the same temp that I use to get. My mileage improved too after that. The thermostat is only like $10-$15 with the gasket so I would definitely try it out since it's so cheap and easy to do.