Gas Mileage Issues on my 04 X5 4.4L
 

So guys here is the dilemma,

As soon as my X5 hit the 100,000km mark it started giving crappy gas mileage. I gauge this because when I use to fill my

tank completely to the top keeping the same driving habits the first quarter tank (at the 3/4 mark) would yield me 200km

where as now it only yields me 170km.

I recently did an Inspection 2 and still nothing. I added a fuel cleaner to clean out the fuel system and still nothing.

Just recently changed an ignition coil that was misfiring still nothing.

Just wondering if there is anyone else with the same issues. I am running 94 octane.

Would the ignition coils need a changing maybe ?

Im at a loss here people

Thanks

Spark plugs? Fuel filter?

All those where change in the Inspection 2.

What sparks plugs did they use though? Others have reported power loss when using Bosch +4 spark plugs as opposed to the NGK's that should have been installed. Just an idea. I've worked for dealerships in the past, and sadly enough, it's not uncommon for them to either not do or "forget" to change something in the effort of saving a buck. Since you had the Insp II done recently, take 10 minutes and pull the plugs yourself and give them a look.

thank you for the insight.

Well I supplied the shop with the NGK Part #BKR6EQUP that where recommended by ECS tuning. Now I dont know what the old plugs where I think NGK but prior to my Inspection 2 I was still getting crappy gas mileage even with my old plugs in and with the new ones there is no change.

I suspect the coils are weak. I remember in my old E36 M3 supercharged I changed the coils and plugs and noticed a horsepwoer increase of 25 to the wheels. Got better gas milage as well so I am thinking new coils ?? Spark maybe weak ? I just had a coil fail on me as soon as I drove from the shop

Anyone else with some ideas

Question--- Up in your neck of the woods, when do they switch to the ~winter blend~ of fuel ? This could play a role as well...

I thought they only do winter blends in diesel?

Just for the heck of it, unplug the MAF and drive it around...see if the power feels better. MAF's degrade overtime and get more resistance in them, just like spark plugs. Cleaning them IMHO is pointless.

Never thought of that. Well we r in the single digits right now so I assume they should have switched to the winter blend already. Not 100% sure though

I was thinking of doing that as well. I did a complete scan of the truck using the GT1 machine at my mechanics shop and everything checked out ok. Would a code not trip up if the MAF was acting weird :dunno: