at 8,000 miles, Gas Mileage dropped 20-30mpt

[ryanpick]

Love the car so far. I've had it since Jan. I commute to work and I have avg 330-340 miles to a tank up until recently. I haven't been driving any different and since I've reached around 8,000 miles I've been getting about 300-310 miles to a tank. Plus the computed mpg that the car keeps track of dropped from 24.5 to 24.2.

After reading M3_Dust's post on Scheduled free maintenance it makes me wonder if perhaps it's time for an oil change. (if so where, what oil, what happens with the on board computers maintenance schedule)

or

Do you recommend some sort of additive that you put in the gas tank to clear any possible build up?

I know nothing about cars and maintenance whatsoever

[Tom K.]

Originally Posted by ryanpick

Love the car so far. I've had it since Jan. I commute to work and I have avg 330-340 miles to a tank up until recently. I haven't been driving any different and since I've reached around 8,000 miles I've been getting about 300-310 miles to a tank. Plus the computed mpg that the car keeps track of dropped from 24.5 to 24.2.

After reading M3_Dust's post on Scheduled free maintenance it makes me wonder if perhaps it's time for an oil change. (if so where, what oil, what happens with the on board computers maintenance schedule)

Since you've only had the car for 6 months, you are not yet entitled to a free oil change at your dealer. You might consider an "interim" oil change, especially if you plan on keeping the car a number of years. But it probably won't affect gas mileage at all. I have mine done by my dealer (usually about $100 which includes a hand wash), and they do not reset the countdown so you will still be entitled to the covered maintenance when you accumulate the mileage.

24 mpg average isn't bad for a 128i, especially since you don't say whether it is automatic, at what speeds you commute, how much traffic, etc. Also, why don't you start resetting the mpg indicator at each fill-up so you can track your mpg for each tankful? You should also probably record the actual mileage and gallons used for each tank and calculate the true mpg to provide a check on the computer.

Has the gas in your area recently had 10% ethanol added? This can cause a drop of a few % in fuel efficiency. And have you switched from premium to regular? 87 octane won't give you the best gas mileage.

FWIW, my 128i 'vert (MT with SP) gets about 22~23 mpg in suburban driving and around on the highway, depending on speed and wind.

Tom