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85' 318i mpg (5 speed)

Discussion in 'E30 (1984-1993)' started by WDWfan1971, May 31, 2008.

    WDWfan1971 guest

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    Thought I would throw this out to everyone. Today I had my first complete fill up. Over the last few weeks I had been toping it off.

    I guess I was worried about driving the car and having it break down. Having no service records from the previous owner, I guess I just wanted to be cautious. After three weeks I am starting to get a feel for the car. The gas gauge can be a little jumpy at times, so I was wondering if it was trully working or not. Today I made it the red area on the gas gauge and I was still runnin', I desided not to chance it and stopped for a fill up.

    It took a little over 9 gallons, so I figured I am getting around 30.9 mpg! So far all I have done to the car is change the oil (Castrol GTX-non synthetic 10-40, we live in Green Bay), oil and air filter. Filling up today I added a bottle of Techron.

    The big question I have been waiting to ask untill I got an idea about the cars mileage is.... the oxygen sensor is disconnected....

    What will happen if I connect the new oxygen sensor that I bought? Currently the car is running great-as far as I can tell. No stutter, plenty of 1.8 liter power.

    I have a new cap and rotor, and plug's ready to go. I'm really concerned with getting the most MPG's I can out of the car-but those on ramps are just so inviting. I guess I really want to car as original as possible, to include a functioning SI board.

    So what's everyone's best guess or input? I do plan to pick up some spark plug wires, but I am looking for reccomendation's as to what kind and what price point so I don't get rooked.

    Thanks for anything you can think of.


    Brent
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    az3579

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    I got my wires for about $80-90 on eBay. They are pretty good.

    I can tell you that after I replaced my oxygen sensor, my mpg improved considerably. I now average about 21 mpg compared to the 18 I was getting previously. This may be in part to the weight my foot lost over the course of gas price hikes, though. ;)


    I can't believe that you are getting 30 mpg. Is that all highway or is that mixed city/highway? That is absolutely amazing for a ~23-24 year-old car.

    WDWfan1971 guest

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    Mostly highway. I have a 23 mile ride to work-mostly highway. The PO said he got better mileage once he added the new "Bro Street" exhaust. It sounds kinda guteral, but I'm beginning to like it.

    So what do you think about the computer? A none issue? The PO just didn't want to spend the money?

    What type of wires did you get from e-bay?

    Thanks
    • Member

    az3579

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    The spark plug wires I got were nothing special, just some random set I found on eBay with a seller that had a really good feedback rating. They were new, and I recommend you buy only new wires to minimize the possibility that they would cause problems.



    As for the computer... do you mean the fuel gauge? Mine does that as well; it jumps around occasionally, but overall it provides a good guesstimate as to how much fuel is left. Definitely not as accurate as the 2002 Nissan Sentra we have in the family. For some reason the gauge likes to jump around a lot; maybe I need to clean the ground or something. Either way, when the needle reaches the top of the red zone and you pumped 9 gallons into it, it sounds about right. I have a 14.5 gallon tank. I always put gas in immediately after the light comes on, at which point I could put in anywhere between 11 and 12 gallons of fuel in. Has your light come on when you put 9 gallons in?

    Keep in mind that the fuel gauge gets more and more inaccurate the emptier it gets. It may actually have a gallon more or less when it's reading that low. Is your gauge mostly accurate or does it never show the right amount?

    WDWfan1971 guest

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    When I refer to the computer, I am talking about the computer that drives the engine. It's an 85' and I don't have a "miles to empty" or anything like that. In my console all I have is a digital clock with a button for minutes and hours.

    I've been told the car is probably an OBD 1, so I'm thinking it doesn't really have a big brain as far as the O2 sensor is concerned, but I don't want to to create more problems if I do put the new O2 sensor in.

    As far as the fuel gauge, I have no idea. From what I can tell it seems close to true. I have no owners manual so I don't know what the capacity of the tank is.

    Thanks
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    az3579

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    I originally thought there was such as a thing as pre-OBD (which there might be but I don't know) and I thought E30's were pre-OBD. It seems there isn't much information on the subject, but I found a post suggesting All BMW's pre-1996 were OBD I and after were OBD II.

    It's an E30 - no harm swapping out an oxygen sensor with a new one. At the most, you're wasting money by buying a new one if the old one is still good, but it's a good preventative measure if you don't know when the current one was replaced last.


    You don't actually need the 'computer' you are referring to, commonly referred to as the "On Board Computer". There were multiple versions; a simple analog clock, a two-button digital clock, a 6-button digital clock with temperature and date functions, and the more complex 13-button on board computer, which was a digital clock, date/temperature meter, and fuel economy computer. It may have done more but I'm not sure seeing as I don't have one. Look at it this way: if this was a necessity, then all the E30's would have it. If your fuel gauge is working acceptably, then you don't actually need one of these. The retrofit would be quite a hassle and is a waste of time, honestly.

    ** note ** ^^ this is a different computer than "the one that drives the engine", which is the ECU in reality. The ECU doesn't actually tell you anything, it drives all of the important stuff necessary to run the car; the engine management system. **
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    FurryOne

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    Why? I'm getting 27 around town and well over 30 highway in an '85 325e (5-spd), and the points, plugs, & wires have never been changed - nor has the cat.conv. (went to a Bosal OEM exhaust) in it's 128K miles.

    WDWfan1971 guest

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    I guess the ECU is what I am refering to.

    So seeing how the current O2 sensor is not connected (at the connection on the fire wall-both wires are tapped up) I should be able to install the new one- negative battery terminal disconected- and it should fire right up?

    The ECU should "learn" from the new O2 sensor, adjust itself accordingly and I should see an improvement in mileage?

    Furry, which Bosal? Mine is the "Bro Street".

    Thanks
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    az3579

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    Well I'm barely able to scratch 22 mpg average and that's with me reeeeeeeally trying.

    All of the tune-up items have been replaced plus other stuff that didn't necessarily have to be replaced quite yet. :confused:



    Besides, I'm finding it hard to believe that 20+ year-old cars are getting the kind of mileage that brand new economy cars are getting with about the same amount of power.
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    kkratoch

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    Where are we talking about? I know some states like OH are mostly flat and would expect higher mileage, but where I am in PA it is mountainous and understandably the car will be less efficient.

    desertVert guest

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    Your car is also an "e" which could explain a higher MPG. The OP has an "i" engine, albeit a 4-cylinder, so a 30+ average seems a little unrealistic.

    In my car I get ~22mpg only if I baby it for mixed fwy/street driving.
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    az3579

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    The OP has an i, sure, but it's a 4-pot. An average of 30mpg is a bit hard to believe in mixed city AND highway driving, but it is entirely possible since he does mostly highway driving.

    I also have an eta, FurryOne, but I can't get anywhere near that mileage if my life depended on it. :confused:
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    jkalgreen

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    30 mpg in 318i is a reality

    I can corroborate the mileage reported on this '85 318i. I have a 1992 318iC, just did my second fill up of the summer. First tank was 30.1, second tank was 30.4. I drive it probably 60% highway.

    Yet another reason to love our e30s.
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    Elkoholic

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    I'm over in the Susquehanna Valley on the eastern end of the PA spectrum...and I get decent milage with the six-cylinder + 5-speed combo...according to the on-board computer (the complex, 13-button one), the average fuel economy over the life of the car is 22.4. That's gone up since I've bought it...but there's no chance that I'm ever completely light-footing it...wild.

    The "Range" button always reveals that I have about "+357 MI" after I first fill up, a value I think is pretty respectable. I generally find that my real-world range has never broken 340 miles, though. I use this car primarily in the city, going to work in the summer, but longer trips to Maryland and the like have given me close to 400 miles per tank!!!

    CHITTY guest

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    I also can say I get 30 mpg out of my 84 318i mainly freeway miles but my 89 328i gets around 25mpg. I personal think it has to due part that the 318i is a lighter car than the 325 and that I drive the 325i a little bit harder. By the way both cars 5spds. and well kept on maintance that makes all the differance.

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