M42club.com - Home of the BMW E30/E36 318i/iS
DISCUSSION => General Topics => Topic started by: seeohngee on October 29, 2009, 06:47:30 PM
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I keep hearing people say they get around 30mpg on the m42 motor. That's definitely not what I'm getting. I'm getting very low mpg and I'm not even pushing the car. Maybe someone might know what's wrong with my motor or maybe how I can get better gas mileage.
Besides my issue, what's everyone mpg?
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Maybe check your O2 sensor?
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After I got my ODO fixed my first tank was 29mpg. On my second tank after I put my heavy 16" wheels and Dinan Chip in I pulled in 26. Im about to fill up for my third tank today or this weekend. It looks to be 26-27. I drive about 1/2 freeway and 1/2 city
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Before turbo: city-28mpg highway-34mpg After turbo: city-25mpg highway-35ish.
Honestly I could probably get better mileage city, but with the turbo in there... it's not going to happen. :)
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Man I'm definitely not getting that much. I'm going to fill it up again in a few days and see. So what type of gas are you guys using? 91 or 93?
Anyone else gas needle move back and fourth?
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I use 89 or 91 octane & I usually see mid-20s city & low 30s highway. I have seen nearly 40 on long highway trips.
I know this sounds stupid, but check for cracked rubber or corroded metal fuel lines...or a rusting tank before you start tearing the engine apart. You have to get under there when the engine is running with a really good light to be sure it's all fuel-tight.
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Thanks Dave. I hope I find time this weekend to work on the car. Are there any links on the forums showering where/how/what to check? I've been searching around and couldn't find much. I'm kinda new to the car scene so I'm not too familiar with cars (I'm learning).
I'm currently only getting 18mpg with mix driving(60city/40hwy):(
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Jorge is right too...bad O2 sensor can really hurt mileage. Plugged fuel filter, bad temp sensor, plugged injectors, timing faults, bad AFM unit...the list goes on and on. I try to start with the free/simple stuff then work my way up on any repair.
It's not too hard to check, more of a 'get down there & do it' thing. It also doesn't cost a dime & gets you to know your car better...also be sure to de-pressurize your fuel system & have no ignition source close if you decide to R&R anything. Gas vapor must be treated with respect as it can ignite in odd ways and surprisingly far from the leak. Plus it takes forever to get the smell off your hands. I always do fuel system repairs outside if I can.
The hard lines run under the driver's side along with the rear brake lines. Just check them for any damp spots. They should unclip if you need to pull them, and you can buy pre-made lengths of steel line at parts stores.
The rubber lines that usually are the worst are in front of the rear wheel with the fuel filter. ANY cracking (like mine), replace them. BMW makes great fuel line. It's expensive but I think worth the extra money (I think it's 8mm I.D./12mm O.D high-pressure line), $10/meter or so. Cut to length & install. I'd use new fuel line clamps too.
There are two other lines that are difficult to inspect...they're on the fuel rail under the manifold. The steel hard lines run up to the engine along the firewall, then vanish under the intake. Get a flashlight & check the two short rubber connections up there. Any gas leaks will evaporate very quickly so do it with the system pressurized (key on, engine off).
Another symptom you might have with fuel leaks is difficulty starting the car when it's been sitting for a while.
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Thanks Jorge and Dave. I'll definitely try to check them out after mid-term is over.
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I get about 28-29 city if I drive long enough for the car to get warm. On short drives to school and such, it's as low as 25 mpg. Highway I've seen 40 mpg average at around 70 mph. That's on 15 inch wheels, a chip, mustang injectors, magnaflow exhaust, etc. Basic mods.
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I like to buy 10 gallons when the light comes on. Then I see a pretty quick read on mileage. Just going back and forth to work for 10 gallons (almost two weeks) is about 250 miles pretty consistently. On the highway, at 70 mph, I think I get almost 320 to 330 (33mpg) miles, but at 80 mph, that drops to 275 or 280 miles (28 mpg). These bricks ain't very smoo-oo-oooth.
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My numbers will vary a little as I have a heavier e36, with 17 inch wheels and pretty wide tires, none of which is really helping the consumption, but I'll participate mainly because I have a question as well.
- Ever since I got this car, I've cared more about miles per gallon than miles per hour, and I've been driving it as such. Easy take-offs and about 70ish (couple more or less) cruise speed on the highway ... consistent 28-28.1 mpg with mostly highway driving.
Well until today I though that was about right given the wider/bigger wheels and tires and the EPA estimate which it matches up with pretty well. Today however I had to go to another city and the highway was wide open as you would expect at 10am ... I don't think I went under 85 anywhere (probably more like 95 average) with quite a few pulls well into the triple digits (don't tell the cops). I came back and filled up and to my surprise it only took 4.2 gallons for 130 miles ... 30.72 mpg.
How exactly does that work that when it's sitting at 4-5k rpm, it's using less fuel than at 3k? :rofl
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do you get loss of power in addition to low MPG with a bad 02 sensor?