[CobraMarty]

My biggest thing is that I want to make my 400 mile work trip on 1 tank of gas. And not have to be running on 'fumes' to get home.
Fill it up, commute, fill it when I return home.

Before in my Taurus at 64mpg gps, commute took 3 hours door to door.
Now with BMW, making the trip at 70mph (cuts 15 minutes off commute) or 75mph (cuts 30 minutes off commute) would be a plus. Although driving faster requires more effort and is more tiring. Have to watch out for the state troopers, slower moving traffic, semis, deer, etc.

My mileage summary-
Tires-225-50-16 BFG g-Force sport comp-2 24.9"tall
25mpg @80mph indicated (75gps) ?26.5mpg corrected
25.44mpg @81mph indicated (75gps) 402 miles 87 octane
27.11mpg @75 indicated (69gps) 87 octane summer blend
CEL at 75mph indicated (69gps) 89 octane, vanos valve, lost 4mpg

New 17" rims Tires Michelin 225-50-17 25.9" tall
22.5mpg @75mph indicated +A/C, longer trip than usual
27.65mpg @70mph indicated (69gps) no A/C
26.55mpg @ 70mph indicated

Added aFe Magnum Force Stage2 Pro 5R intake
25.29mpg 75 1/2 trip/ 65 1/2 trip and heater on, winter blend
25.00mpg @70mph indicated (70gps) 30-35*, no heater or defroster

Mobil 1 5-30w oil and filter change 96k miles
26.18mpg @70mph indicated (70gps) 35* minimal heater/defroster, some slower due to fog

[hassmaschine]

Is there a lot of traffic in your commute? is that 400 miles mostly all at once? (200 each way).

I'm surprised you aren't into at least the low 30's - not sure what it is about the 328's. our 325xi (6mt) consistently did about the same fuel economy as my 330i - it could easily hit mid 30's on a long highway trip (even running 87 octane, which kills performance but doesn't hurt the engine).

Oh I get it - auto. Man, surprised it kills the economy so much (but again, I'm not).

[CobraMarty]

Yep, auto and xi.

Minimal traffic, all turnpike or highway, non-rush hour.

I hate traffic, for someone who grew up in Los Angeles.

[mecheng77]

Originally Posted by hassmaschine

Is there a lot of traffic in your commute? is that 400 miles mostly all at once? (200 each way).

I'm surprised you aren't into at least the low 30's - not sure what it is about the 328's. our 325xi (6mt) consistently did about the same fuel economy as my 330i - it could easily hit mid 30's on a long highway trip (even running 87 octane, which kills performance but doesn't hurt the engine).

Oh I get it - auto. Man, surprised it kills the economy so much (but again, I'm not).

I agree, fuel economy should be higher and no auto shouldn't kill it that much.
I can get low 30s easily on the highway at 120km, but I use 91 octane.

Try switching to 91 Octane for a few tanks (until computer adjusts) and record fuel economy.

I think long term, 87 could damage the engine slightly as it could still ping on occasion, especially during load and there is only so much timing retard it can do. I would recommend 89 minimum.

[hassmaschine]

nah. It doesn't hurt it in the slightest. the DME is setup to run on 87 out of the box, the timing isn't aggressive at all. It just never uses the 'high octane' maps, so torque is reduced.

I've yet to see an auto break into the mid 30's, so it appears that it does indeed affect fuel economy significantly. more weight, more drivetrain loss, and shorter gearing.

[atmosphericM]

Change your final drive to the MT ratios? lol

[mecheng77]

Originally Posted by hassmaschine

nah. It doesn't hurt it in the slightest. the DME is setup to run on 87 out of the box, the timing isn't aggressive at all. It just never uses the 'high octane' maps, so torque is reduced.

I've yet to see an auto break into the mid 30's, so it appears that it does indeed affect fuel economy significantly. more weight, more drivetrain loss, and shorter gearing.

I got 34 mpg, last weekend. It was warm (for winter that is) 8C, using 91 octane, with one passenger.

[tlow98]

Originally Posted by mecheng77

I got 34 mpg, last weekend. It was warm (for winter that is) 8C, using 91 octane, with one passenger.

What you guys use imperial gallons up there?

I've never seen above 28ish and that's going slightly downhill, but moving quite fast (80mph+).

What kmh were you driving?

[hassmaschine]

I had a photo of our E91 with 300 miles at 1/2 tank, and 280 miles left on the range (do the math). Unfortunately that SD card got corrupted, and that car was sold.

now we have an X5 that gets... 12.

[tlow98]

Originally Posted by hassmaschine

I had a photo of our E91 with 300 miles at 1/2 tank, and 280 miles left on the range (do the math). Unfortunately that SD card got corrupted, and that car was sold.

now we have an X5 that gets... 12.

My E91 routinely gets 13-14 with incredibly short, hilly drives in SF, so I know how you feel

[mecheng77]

Originally Posted by tlow98

What you guys use imperial gallons up there?

I've never seen above 28ish and that's going slightly downhill, but moving quite fast (80mph+).

What kmh were you driving?

I'm more comfortable with mpg even though we are technically a metric country
I changed my settings to mpg from l/100km my configure menu.
Pretty confident that it is US gallons

I was driving 110-120km/hr

Car has only 107,000km, original plugs, new air filter and trans filter

In the city, mpg is much worst but I like ds mode

[tlow98]

Originally Posted by mecheng77

I'm more comfortable with mpg even though we are technically a metric country
I changed my settings to mpg from l/100km my configure menu.
Pretty confident that it is US gallons

I was driving 110-120km/hr

Car has only 107,000km, original plugs, new air filter and trans filter

In the city, mpg is much worst but I like ds mode

That mpg makes sense given the speed.

[CobraMarty]

Car has 97k on it. The GM auto trans is working fine but at times it seems to have a 'funny' sluggish shift.

Taking it to the Transmission shop for a trans flush and filter.
See what they think and offer.

[CobraMarty]

Latest 26.24mpg at 70mph indicated(69gps).

[tlow98]

Lots of people think ‘flushing’ any trans might not be advisable. I’d tend to agree.

There’s a lot of internet heresy on the matter but safest bet is likely a drain and refill.

You tried looking for a manual trans car? I’d bet they would make the distances you’re looking for.

[CobraMarty]

It's at the trans shop now. They have done work for me in the past and I have had good results with their recommendation.

'Trans flush' vs 'Drain and refill'.
That is a ongoing debate. New filter, gasket and check magnet for metal is all good.
Synthetic ATF, another question.

[CobraMarty]

Had a CEL come up on the way to dropping off at the trans shop.

P0128 Code

I've had this code come up twice now. Reset and gone for a few weeks, now again. Has come up when it has been very cold out, around 35*.

P0128- Coolant Thermostat (Coolant temperature below thermostat regulating temperature)

Does anyone have any experience with this code?

Sensor or thermostat?

If the thermostat is bad and the engine never gets up to operating temperature and runs in 'Cold' warm up mode, maybe that is the reason for poor mileage. IDK?

[tlow98]

It certainly could be a reason, but I don’t feel that your that far off optimal mpg, given you have an auto awd car.

[nsjames]

awd costs at least 1mpg.

I average about 27 in my e91 xi.
thirty is a pipe dream.

[CobraMarty]

Picked up the car tonight and on the drive home definitely shifted smoother, crisper and nicer. But really too little time to really get a good feel for it.

So I did hook up the scan tool and watched the ECT. Driving all warmed up was seeing 165-167* and jumping on it the most I saw was 172*.
So that's not right.
I think that the P0128 code is that I have a bad/stuck thermostat. Ordered a new one from ECS. Will fix it next week.

This could be causing some of the poor mileage.
It is running too cold and is in 'warm up' mode. IDK?

[tlow98]

Originally Posted by CobraMarty

Picked up the car tonight and on the drive home definitely shifted smoother, crisper and nicer. But really too little time to really get a good feel for it.

So I did hook up the scan tool and watched the ECT. Driving all warmed up was seeing 165-167* and jumping on it the most I saw was 172*.
So that's not right.
I think that the P0128 code is that I have a bad/stuck thermostat. Ordered a new one from ECS. Will fix it next week.

This could be causing some of the poor mileage.
It is running too cold and is in 'warm up' mode. IDK?

Quite possible. Mine is almost always 200 or greater. Sometimes it will go lower in response to lots of throttle.

Pump is in the same area - most people replace both if they go in for one. Personal choice, of course.

[hassmaschine]

yeah, a cold thermostat will definitely affect fuel economy. If the engine never reaches a certain operating temp, it will always be in "warm up" mode, which uses more fuel. It's not going to be a *huge* difference thanks to the wideband O2 sensors (cat warmup uses a lot more fuel frankly anyway), but it could be a couple percent.

FWIW, I didn't replace my thermostat when I did my pump. I guess I figure my E90 is a cheap enough car it doesn't matter - it's not a Ferrari, lol - and the stock thermostat was working, so I left it alone. Also, the new ones are plastic which is usually shittier. But as much work as it is to get to, I'd do the pump as well if I were in your shoes as well - unless it was recent (N52 pumps should last at least 90-100k miles, unlike their N54 brothers).