Whiskey Bravo

Can anyone explain why, 3 years and 100,000km in, my 2011 JK Sahara just decided to jump 2 litres to the 100km? (Sorry, up in Canada here...)

I've got tons of mods that affect mileage: 35" tires, 3inch lift, steel front and back bumpers, K&N filter.

Thing is, they've all been in 2 years. Filter is clean, oil is changed (mobil1 synth 5w20)

My driving habits are also the same... Other possible factor is cold weather, but i figured cold air would be a boon, no? Also it didn't jump up last winter...

I've taken into account 4wd for snowstorms.

Thanks!

Jiblet

I don't speak Canadia. (Just teasing) Are you saying your gas mileage improved?? Or got worse?

Worse is expected. We get winter blend fuel in many states the reduce pollution. But even without that, colder temps cause the PCM to run a richer mix. And run the richer idle mix longer until warmed up. So usually winter means crappy mileage. Or crappier....eh?

rob_engineer

I track mpg for very tank of gas. I now have 41,000 miles on my 2012. Weather in NJ has been extraordinarily cold this January. My mileage has dropped like a rock. Went from about 17 mpg down to about 15 mpg. Cold weather, winter blends, warm up period all add up to lower mpgs.

Whiskey Bravo

Hmmm, thanks guys. I really thought the cold air would help. The warm-up time is really not that significant in the greater scheme of things though. I think it's probably the blend if not the air being too cold.

Lets hope summer brings more acceptable mpgs again!

karls

With the cold weather you *should* put a higher grade fuel in since the air is more dense. The fuel doesn't burn quite the same and could create an issue. I don't put a higher grade fuel in, I just deal with the loss.

Jiblet

I'm not sure about changing the octane for winter. Never heard that before. I *thought* higher octane meant lower volatility! which would work against you in colder weather... but I really don't know. Anyone? Thoughts?

I do know the problem in winter is the cold depresses the vapor pressure of the gasoline. So winter blend has butane added to it to increase the vapor pressure. That's bad enough but the computer also enriches the fuel trim to account for denser (cold) air. That plus longer warmup and longer idle times (especially when people warm the car for their comfort) add up to lower mpg.


I was confused at first by OPs use of liters per km. Not the metric part but the use of volume per distance. I'm so used to distance per volume (mpg) that I confused myself. We can expect to see a change to volume per distance over the next few years. I think it's starting to show up on new car window stickers as X gallons per 100 miles. It's a more intuitive method of comparison. They say....

Whiskey Bravo

You guys should just switch to metric already!

karls

Jiblet, pulled a snippet from the internet >>>

"You could actually get a bottle of octane booster and run it through a tank while it's still cold out. See if any engine sounds or pinging may improve. As colder weather will cause combustion temps to rise and result in pre-ignition and detonation. (Also referred to as pinging or valves rattling). Pulling you plugs will he a good indication as to the combustion conditions."

Jiblet

Are you saying USA, Liberia, and Myanmar are behind the times?!!





Actually, I agree, I'm a scientist, metric is so much easier.

Jiblet

Interesting.... I'll have to look into this some more