[2PInZ]

Hello, I’m new to the e90 forums but have been going through the many great previous threads as a guest for a few weeks now in order to get a better idea of what the e90 was all about before I decided what vehicle to purchase. After a long search, I was able to find a clean, well-maintained 2007 328xi black/black with around 96,000 miles, loaded with iDrive and all from a private seller for about $11,500 – which I am very happy with. I just moved up to Scranton, PA from Northern Virginia on Sunday for grad school (three days after buying this car), and despite the estimated 17 city and 25 highway MPG cited for this car by the government, I was able to get:

31.3 MPG over a 3:54 trip, covering 222 miles with an average speed of 59.7 mph.
Weather: Slight drizzle rain for the first 30 min, clear after that.
iDrive photo image is attached.

I’m not sure how great of an accomplishment this is or anything like that, but I thought I would share whatever pieces of information I could that might have contributed to this with you all if in case you were having poor gas mileage, or at the least just as another set of data for other owners to refer to at some point for whatever potential tangent reasons/ideas. The person I bought it from was a mechanic, so he had done an oil change and put in a new battery before he gave it to me. I will first list the things I did to the car, then I will list the things I do when driving that I believe might have made a difference. Here are the 4 things I did to the car (in order) after bringing it home…as a student of science, I will write everything I did – I’m not trying to insult any of your intelligences . Keep in mind, I’m no mechanic!

1) Cleaned engine bay. I removed the microfilter casing (tutorials for replacing your cabin filter are on YouTube, it’s probably the easiest DIY) and first took a rag to brush off all the dirt/leaves. Then I used a vacuum cleaner’s suction tube to pick up whatever I missed (including the crap that is in the pockets under the hood close to the bottom corners of the windshield…not sure exactly what they are but there was a lot of trash there for me). After All the big pieces were out of the way, I took paper towels and a regular all-purpose cleaner which also said it removed grease and just sprayed down whatever I knew was safe to spray down, let it soak in for about 30-45 seconds, then sprayed more cleaner in a paper towel and just wiped down as much as I could. I was too afraid to hose down the engine bay just because I know these cars have a lot of electronic gadgets, but I will go ahead and say I was very happy with the results (for those of you who don’t want to hose).

2) Power Steering Fluid Change. After cleaning the engine bay, I first picked up two turkey basters ($1.68 a piece), and then I picked up a can of Pentosin CHF-11S power steering fluid ($22). I followed a YouTube DIY by ‘AskTheCarExperts’ – if you search ‘e90 power steering fluid’ it should come up. The only difference was that 1) I used a turkey baster, not a suction machine…so it was slower and I had to be a bit more careful but it worked, 2) I did not use half the can when he refills the reservoir after removing the old fluid, I refilled it to a little under max, 3) instead of turning the wheel right once and left once to flush out the remaining old fluid, I drove the car around my block one time, making sure the wheel had been turned all the way left and right at least twice, and 4) I did this all twice, not just once like in the video (removed old fluid, added new, removed new + rest of old, added new again, removed newer + rest of old, then added the final amount). This made an immediate significant difference in my steering as the fluid I was removing was pretty dark.

3) **Continental ContiProContact SSR RunFlat Tires (Stock, very low mileage) – I think most important. When I had picked up the car, these were the tires that were on it. I was a bit surprised that the tread was pretty much brand new, but I figured the previous owner must have used different tires of his choice and just thrown these back on during the sale. The problem was that whenever I accelerated or decelerated in the 25-40 mph range, my car tires would vibrate. I searched heavily online as to what could be causing this because my steering wheel wasn’t shaking and the car was moving dead straight so it wasn’t an alignment issue. There are several threads in this forum about this exact vibration and owners having their like-new cars being torn apart to try and fix it while under warranty…along with the many anti-runflat tire threads. It’s safe to say the vibration was so annoying that I almost started regretting buying the car because no way could I spend any more to buy new tires (which seemed to be the only solution from searching online). The last idea I had was to go to Costco and fill the tires up properly, not using the cold PSI amounts listed on the door panel (32 front/36 rear). When I got there, the tire specialist looked at my tires and filled them up +5 PSI (37 front, 41 rear) – this was done on a summer day after my car had been sitting in a parking lot for almost 5 hours in 78 degrees, and being driven about 6 miles to Costco. I’m writing this so that you can make your own judgment because obviously I’m not sure if you want to get 37/41 on a 55 degree night or something. After listening to my complaint, he said he had heard the same story from another e90 owner in the past, and then suggested that I balance my tires for $4 a tire. I figured $4 wasn’t bad and was worth a shot – and oh my what a difference, the vibrations were completely gone. I went from hating these tires to loving them after driving around in them for a few days balanced. I would highly recommend Costco's tire center...my family's been going to them for years now and those guys really do a thorough job (just my opinion).

4) Fuel Injector Cleaner by Chevron ProGard - $8. I wasn’t sure if the previous owner had been using premium gasoline in the car all the time, so I first used one whole tank of premium, then dumped this whole bottle in the second tank of premium when there was around 20% gas left in tank. This stuff is supposed to remove gunk from your fuel pump and injectors, and apparently this additive is the only one that’s proven to actually make a difference (what I read on this forum).


I wanted to do an oil change after using the fuel injector cleaner just because I figured that whatever gunk was removed by the cleaner must now be in the engine, so why not clean out the engine - maybe with a Forte product or something? Either way – moving on, these are the 5 main things I did while driving this car that might have contributed to this result:

1) Take your time accelerating up to highway speeds. The first thing I noticed about e90s was how quickly they respond to the gas pedal, which is a part of what makes them so fun. There’s a point when you push down on the pedal where the car goes from gradually accelerating to transforming into a speedster – I’m sure everyone here knows what I’m talking about. When you are merging onto the highway and while on the highway, do not breach this point on the gas pedal! You will know if you breach it if the MPG meter drops to as low as it can get. Stay on the nice and easy side. At first it seemed pretty boring and like I was holding back but to be honest, I was surprised at how quickly the car got up to highway speeds and maintained them without having to really be pushed.

2) Give gas periodically, don’t hold the pedal down. If you are following traffic, moving at a nice comfy speed, and just trying to maintain your speed, there’s no need to hold down the gas pedal even if it’s slight. What I do is give the car some gas - maybe till the MPG dial drops to around 30 MPG- then I let go.

3) When moving on a straight way or slightly uphill highway, watch the MPG indicator. There were many times where I was going slightly uphill or needed to speed up to change lanes or something, and in those moments I would give more gas but would just let go of the pedal when the MPG dial would drop down to either 30 or 20ish. Of course you can’t be perfect and safety comes first – do what you gotta do. Sometimes you will come to a hill and the car will drop to a lower gear and you’ll burn gas – and that’s fine…but if possible, give gas in shorter intervals while watching the MPG dial, trying to not let it go below 30 or 20 MPG.

4) No need to be in the passing lane all the time. If there are cars trying to go 15,20,etc. mph over the limit, let them pass! If there’s a car in the slower lane that’s going 9 or 10 above the speed limit, don’t feel antsy and pass them for no reason. Get in the slow lane if things are moving there fine, and exercise #2 ,3, and 5.

5) Lay off the braking, anticipate. Besides maintaining a decent space between yourself and the car in front of you, be aware and anticipate potential for traffic to slow down. If you see a guy unnecessarily zip past you like an egghead and there are quite a few cars in front, anticipate him cutting back into your lane and freaking out the drivers in front of you – eventually resulting in you having to slow down too. When he zipped past you is when you should not be ‘driving to pass,’ you should anticipate having to slow down and let the car slow down on its own and then speed back up instead of having to hit the brakes and then hit the gas from a much lower speed.

If you guys have any suggestions/comments for me to improve my MPG even more, I’d be eager to read them. Feel free to post any comments and questions. I’m loving the car, and I plan on keeping it in good enough shape till 300k miles.

Cheers.

[ophale]

Congratulations on your BMW! I'm a scientist and I appreciate your detailed discription and analysis.

Perhaps the information below will help you in assessing your recently achieved mileage.

I've been tracking my new to me BMW for ~10,000 miles. Here is some data I can share:

1. Mechanical
E91 (2009)
N52 NA 3.0 liter engine
Rear wheel drive
6 speed manual transmission
~18,000 miles
Yearly oil changes (BMW maintenance program)
OEM run flat tires
Tire pressure maintained at ~40 psi
100% OEM (no modifications, except led angle eyes)
95% Costco premium fuel (10% state mandated ethanol)
20% AC in use
Windows open 50%
Sunroof open 10%

2. Geographical
80% country roads
20% residential/small town
2500 ft. Elevation gain/lose most trips
Weather
Temperature 50-90 deg F
Wind 3-10 mph

3. Behavioral
10% aggressive
60% responsible
30% hyper mile

4. EPA Estimate
17 city
20 combined
27 hwy

Mileage scatter plot for my E91:

n=25
Mean=28.67
Std Dev=0.941



Fuelly has great mpg data here:

http://www.fuelly.com/car/bmw/328i

Just for fun here is the scatter plot for our 2011 MINI Clubman S:



Congratulations on your BMW! Continue with your science education, we desperately need more STEM (Science, Technology, Engineering, Math) students in the USA. I believe a higher concentration of STEM students will increase the competitive advantage of the country, and allow for a more scientifically informed citizenry.

Aloha from the BIg Island Of Hawaii!
https://www.airbnb.com/rooms/539081

[Tom K.]

OP, congrats on great mileage. But to confirm it, you should probably check the accuracy of your OBC by comparing it to the calculated miles traveled divided by gallons used over at least 5 fill ups. The computer MPG in my '07 E91 has averaged 2.8% optimistic since I purchased it in 2010. Which is much better than the nearly 9% optimism found in my '99 328i over 97k miles.

Tom

[ophale]

My experience with the on board computer has been very slight optimistic values at ~0.3 mpg to the calculated values as you described in your post and I reported in the scatter chart. I have always hand calculated my mileage and plotted the results for all my vehicles since 1984. For me, it was a way to determine the overall health of the vehicle, or an "early indicator", of needed maintenance and/or mechanical problems.

You can review my calculated data on fuelly:

http://www.fuelly.com/driver/ophale/328i

Or I can forward you my spreadsheet...

Aloha from the Big Island of Hawaii
https://www.airbnb.com/rooms/539081

[Harry335i]

Sorry, I have ADD, 31mpg and what?

[melloww22]

I avg 17.4 MPG on a FBO e90 335

Anything above a 20 would be awesome for me.

[BMWUltimateDriv3r]

I also have a 328xi and I beat those highway figures without even consciously trying.

[ping65810]

I average 31.7 MPG if I cruising the highway alone, and about 23 MPG around town. My average over a tank usually ends up at 26 MPG with mixed driving though. Mine is a stock 2007 328Xi manual.

[3000GT MR]

I average about 16.5mpg city and 24mpg highway and less when I'm passing people like you ;-) Don't worry i envy. I wish i had it in me to be more conservative. Nice observations and write up!

[VTECaddict]

Good advice, but a couple things.

Originally Posted by 2PInZ

4) Fuel Injector Cleaner by Chevron ProGard - $8.

What you want is the Techron Concentrate. The ProGard one is a diluted version and not as effective.

Originally Posted by 2PInZ

2) Give gas periodically, don’t hold the pedal down. If you are following traffic, moving at a nice comfy speed, and just trying to maintain your speed, there’s no need to hold down the gas pedal even if it’s slight. What I do is give the car some gas - maybe till the MPG dial drops to around 30 MPG- then I let go.

Constant throttle is best to save fuel, unless you start employing some advanced hypermiling techniques. Cruise control is best on flat ground to maintain speed and save gas. Maintaining a constant speed requires less power (and thus less fuel) than constantly adjusting throttle and letting the car speed up and slow down. Cruise control will burn more gas on hilly roads though as it is programmed to aggressively maintain constant speed.

What was your typical cruising speed on your trip? How about your manually calculated MPG? The trip computer has been very inaccurate in my experience.

[Meeni]

Yeah this is typical for an N52. You can even see over EPA ratings very often on the interstate, especially cruising low speed like 55-60.