Author Topic: Gas Mileage (Read 9512 times)

LeeThompson · « **on:** March 13, 2010, 01:18:25 AM »

I only get a mere 19 maybe 21 miles to the gallon.
I have a Dinan Chip installed that came with the car.
Is that chip causing me to loose gas milage?
I put in the high grade gas 2 weeks running and I do get better mileage but when I do the math Its better to stick to the low grade.

On a full tank I get about 250 miles give or take a few miles never less than 240 rarely higher than 270. Excluding a trip to VIR which got me 350 miles haha. I never run it it to the light and I calculate it at a 13 gallon tank.

Is the chip killing the gas mileage and should I put back the old chip?

I drive the all to known e30 318is

tjts1 · « **Reply #1 on:** March 13, 2010, 02:24:42 AM »

Do you drive a lot of short trips with lots of cold starts in between?

BlueBMW · « **Reply #2 on:** March 13, 2010, 07:39:14 AM »

I seem to get about 270 to 290 on a tank and its usually about 10.5 gallons to fill it up each time. That's mostly city driving with just a little highway each day.

Whats the tune up condition of your motor? Have you done the whole mess under the intake etc yet?

BlueBMW · « **Reply #3 on:** March 13, 2010, 08:27:22 AM »

Quote from: LeeThompson;89370

I calculate it at a 13 gallon tank.
I drive the all to known e30 318is

How are you figuring 13 gallons? I usually fill it up full, reset the trip counter, then when I fill up I look how much it actually took to fill up which is usually 10.5 when the light comes on. That could be why your numbers are off.

LeeThompson · « **Reply #4 on:** March 13, 2010, 09:34:16 AM »

Well I don't mean to be a smart ass but I look at the amount I put it. Its usualy 12 something but I figure because I do not run it into the light that its a 13 gallon tank.
I always fill up my car. Sometimes I will leave my card on my bed side table and only have a little cash but usualy I fill it up and reset the trip.

Depending on what you mean by short. Um Well I drive about 40 miles to school and back. And depending on the day I drive from one campus building to anouther. Then always to my step dads shop which is about 5 miles then the 40 mile trip back home then a 10 mile trip to work and a 10 mile trip back.

Yea the motor more than most likely needs to be tuned up. We got it and have not done much with it except for oil change, brake change, tires, and stuff like that.

BlueBMW · « **Reply #5 on:** March 13, 2010, 11:07:01 AM »

If you have some air leaks and are getting some unmetered air into the engine, more fuel will get dumped in to compensate so that could be one culprit of the lower fuel economy.

4banger · « **Reply #6 on:** March 13, 2010, 12:39:34 PM »

my milage actualy increased when i chipped my cars. belive it or not i moved up to 21lb/hr injectors and my milage didnt decrease. best ive seen was about 320 miles out of a tank and that was on a highway trip to indianna last year. i average around 280-290 miles to a tank.

s_ribs · « **Reply #7 on:** May 17, 2010, 04:27:34 PM »

Quote from: 4banger;89384

my milage actualy increased when i chipped my cars. belive it or not i moved up to 21lb/hr injectors and my milage didnt decrease. best ive seen was about 320 miles out of a tank and that was on a highway trip to indianna last year. i average around 280-290 miles to a tank.

I've seen an increase in mpg every time I add a chip, and again when a good cat-back system is built/installed.

My last car, '95 540i 6-speed, increased about 2 mpg after a cat-back set up was built and another 2-3 after a Dinan chip upgrade.

OP-
Need to check maintenance items as well as considering time spent city vs. freeway driving. Anything related to air/fuel measurement as well as their delivery will influence mpg and performance.

Air:
Intake leaks (vacuum hoses, intake manifold gaskets, etc.)
Air filter

Fuel:
Fuel filter
Fuel pump
Lines good and not leaking

Measuring components;
O2 sensor [ecu makes fuel adjustments based on exhaust gas]
AFM (air flow meter) [measures air going in]
Coolant temp sensor (in radiator) [measures engine temp and ecu adjusts accordingly]
TPS (throttle position sensor) [tells ecu how to adjust fuel according to throttle position]

Those are the basics. Lots of small contributing factors but that'll get you started on maintenance items.

RED IS 91 · « **Reply #8 on:** May 17, 2010, 04:59:35 PM »

I just did a 600 mile trip.Everything is stock on my car.I was doing 85-90 most of the time and I averaged 25 MPG. I've gotten 30-35 MPG when I keep it around 55-65 MPH.
The sound of the motor when it get above 4,000 RPM is almost as good as sex.

BUT NOT QUITE

Ryann · « **Reply #9 on:** May 17, 2010, 08:58:47 PM »

How's your alignment? Tire condition/inflation pressure? Jack up your car and check for brake and bearing drag. Throw some new plugs in it and avoid cheap crappy gas.

I always start with the easy stuff and go from there, which I suppose you may have already done. If so e-slap me.

PumpItUp · « **Reply #10 on:** May 17, 2010, 10:16:21 PM »

my bridgestones are the best 14" all-season tire one could ask for. but they seem to give me crappy gas mileage. tires/alignment.. its not some myth or nitpicking. if i replaced my tires with falkens or whatever, it's very conceivable to get 2-3mpg more. but yes, on an old car you should pay bigger attention to induction/injection/combustion, etc. than if you had an e46

MrSlacker · « **Reply #11 on:** May 18, 2010, 10:58:46 PM »

I think I got 310-320 miles out of FULL tank. I accidentally overfilled it and then drove till light came on + 15-20 miles. I get about 22-23 MPG of mixed city/highway, lotsa stupid high revving shifts and general messing around. My E30 is 100% stock.

Ryann · « **Reply #12 on:** May 19, 2010, 12:20:12 AM »

Quote from: BlueBMW;89379

How are you figuring 13 gallons? I usually fill it up full, reset the trip counter, then when I fill up I look how much it actually took to fill up which is usually 10.5 when the light comes on. That could be why your numbers are off.

FYI: According to my factory documentation our e30/m42 tanks have a 14.5 gallon capacity, so based on BlueBMW's info the light comes on with 4 gallons in reserve. At 25 mpg's that's another 100 miles with the reserve warning light on!

Murdul · « **Reply #13 on:** May 19, 2010, 05:24:04 PM »

Have you checked your mileage driven by GPS instead of using your trip odometer? Maybe yours is turning over slower than it ought to. I know this happens because mine was turning over 1 mile for every 4 or 5 driven. I am not saying yours is this bad, but worth checking your calcs.

LeeThompson · « **Reply #14 on:** May 19, 2010, 11:40:05 PM »

Murdul the odometer was rebuilt and reset at 190,000. It was around 184,000 and we guessed the actual mileage.

Ribs the Vacuum hoses have all been replaced under the manifold (a pain in the arse by the way) along wit hthe air intake being cleaned out. Something was living up in there but that has not helped my milage problem.

Ryan i know what you read but when I run it to the light and even miles afterwards I get about 13 gallons Also I divid what I put into the tank by the mile on my odometer and get my milage.

I just took out my chip a few weeks ago. But I am going to Roebling june 11th so I will put it back in. But I noticed a reduction in gas milage with the 93 from the low grade. I am retesting the lowgrade to see if I was mistaken. But however when I had my chip in 93 did give me about 2 or 3 more miles than the low grade.

Car does need to be re-aligned I am replacing the front tie rods or atleast trying to. Finding the time to leave my car for 3 hours is hard :-/ But the tires trhemselves are basicly new.

When I went to VIR I got well into the 350's maybe even 360. But that was all interstate.

It would not hurt replacing all of the plugs and what not.

What I may do is fill it up till it spills. Drive untill I just give out of gas. When I get to the light throw a small gas jug in the car. can't hurt to get the actual tank size.

Thank you all for the replys I hope to see some of you at the trace one of these days