New N63 Engine - Worse gas mileage?
 

Hi All,

I recently went through the engine replacement nightmare, fortunately during the last couple of months on my CPO. My replacement did not was not really related to the BANG settlement. First I had my valve seals replaced, then on my way home from that repair, "something" failed and I had metal shavings clogging my vanos sensors. BMW had been providing me a rental car for 4 months prior to getting a new engine. Finally, about 4 weeks ago, they let me know that a new engine came in and they were going to install it. I've had the 2013 X5 5.0 for about 2 weeks now and everything seems to be performing just fine with one exception. I've noticed that my MPG is lower by 1-2 MPG. Prior to the engine replacement i was getting about 14-15 MPGs. Now, I am getting 12-13 MPGs. My driving has remained consistent. as with the old engine. If anything, my driving right now is more conservative as I feel like I need to break in the engine. So spirited driving has been virtually non-existent.

Is this something I should be concerned about? Or just a slightly annoying anomaly?

Thanks

New N63 Engine - Worse gas mileage?
 

Hey Tallen234,
In my years of building and rebuilding engines I always find that a new, “tight” engine takes some miles to break in and achieve its best (gas mileage) performance.

My guess, within probably 10k +\- miles that you’ll notice the engine starts to “loosen up” and you see that gas mileage go up a bit [emoji106]

Thanks for the response! On a related note, how long (if at all) should I baby the engine? I've been driving pretty mellow for about 500 miles.

At 500 miles I would say you are pretty much there, if you want to err on the side of extremely safe, being a turbo engine with intricate oiling, you could go as many as a 1000.

That said, you’re probably good to go, keep an eye on your oil level as you start to run it harder, since you will be putting a more “aggressive” load on the motor and turbos, just to make sure everything is solid.

In the past I've been told and believe it's good general advice, no full throttle acceleration, vary engine load and RPM as much as you can and keep an eye on engine oil level and engine temperature.

What did BMW recommend for new N63 engines in the day?

If it's a brand new engine, I'd not expect full fuel economy until it's broken in a bit... I would keep in mind that while the engine may be new, all of the peripheral components & sensors feeding input into, & receiving outputs from the DME are NOT new, where it may take a bit of digging & diagnostics, at home in the driveway on your own dime, to find that some sensor, or actuator, or vacuum line is acting a bit old, but is still within acceptable range to not raise any alarms by the dealership's diagnostic tools...

During the break-in period, don't be afraid to give it moderate load using manual shifting to properly seat / bed the piston rings, just don't rev the piss out of it (or lug the engine at low RPM)... Basically, drive as you normally would as if the engine was already broken in, definitely don't pussy foot it, but also don't stomp on it & get the RPM's high. Change the oil & filter right after the break in period regardless of what anyone says...

High power / performance engines don't seat the piston rings well w/ light loads, where the light loads can cause the rings to never seat well against the cylinder walls, regardless of how hard you push it after the break-in period, where higher than normal blowby & oil consumption is the end result for the entire life of the engine...

During engine break in, there is the obvious element of "wearing things in a bit" to make a nice seating; however, what most folks don't know is that this period also helps to further stress relieve the crank, connecting rods, & other engine components that receive a high tensile / strain load due to engine harmonics (where higher RPM's have modes of resonance that are significantly higher in torsional strain due to these harmonics). Revving the engine to high RPM, especially under load, always causes high tensile / strain at specific RPM bands from torsional harmonics, which can lead to fractures, cracks, minor weakening in these brand new components that are not yet fully stress relieved, where the harmonic damper is tuned to keep these dangerous torsion harmonics only down to the level that a properly stress relieved component can handle. Stress relieving of most steel alloys is typically performed at much higher temps, over only a couple of hours, than what is found inside the engine; however, at the 200F temperatures that an engine typically runs at, stress relieving does still occur, & is well documented to occur even down to temps as low as 150F for some steels, albeit at a MUCH reduced rate into the hundred - hundreds of hours, & is probably around the calculated hours for someone to drive the recommended break in miles...