Improving fuel economy

[sandlock]

based on what you explained nando, even if i did have a 3.25 LSD in the car, which i have purchased, thinking i'd be at a lower rpm thus save more fuel, it still really wouldn't help because i'd need to be around 3500 anyway to hang in the motors sweet spot for efficiency. would that assumption be correct?

[nando]

right, it would just move the sweet spot to a different speed, or a different gear for the same speed.

[iwantspeed]

something is not right in my e30
1989 325i 5speed
150 miles out of a full tank with 60% freeway driving 40 % street driving
running 91 octane
Jim Conforti chip
lowered on H&R cup kit
17X7.5 Kopi Alpinas
Hot air intake.

[sandlock]

yea that's terrible. i'd refer to the post on the previous page concerning a thorough tune up/top end refresh. if you aren't running on 4 cylinders and have a check engine light, then you could possibly have an o2 sensor problem turning into over fueling among other things. goodluck figuring it out.

but there is good news, i avg'd 27mpg on my first full tank with my conservative (light on the passing) highway driving. with my 4.10 i cruise at about 74 or so for the sweet spot. i may just sell the 3.25 or keep it in the parts stash...i'm thinking it would give me a sweet spot another 8-10mph higher up since the gear range would be longer, and on the lower gears, i'd just stay in 3rd around town. both would work just in different ways.

[enigmaticdream]

I have a stock 87 325is with a busted odometer/tripometer. Ii get about 23-24 off of estimations based on mpg from the ecu and the amount of petrol I use when fueling up. I do a lot of highway driving. Driving 70 instead of 80 increases my fuel economy around 3-4 mpgs. This is according to the gauge in the instrument cluster.

For people only getting 250 miles a tank. How many gallons of petrol is going into the tank when at the station? I get around 250 a tank but I suspect that my fuel sensor is faulty since I consistently fill up with 9-10 gallons even though I'm almost empty.

For people shifting to the highest gear quicker (i.e. 5th going 35). That doesn't necessarily mean you are going to be getting better gas mileage. If the rpms are too low and you are going up hill for instance. You are going to be putting more strain on the engine than if you have it in a lower gear. My suggest is knowing what gear is best at what speed.

[thereisnoyun]

I've consistently getting 24 mpg on all 3 e30s. gf, mine and gf old car. 60% high way and 40 local, or 70% highway, and 30 local, its always around 23 or 24 mpg. They are all well maintained m20s and all i engines.

[craiggroves91]

I have an 89' 325is and I drive almost all city with occasional freeway usage an I get 200 miles on full tank. I do have a lead foot though.

[e30trooper]

i got 65 miles on my eta , with 10 bux (3.3 gallons ) shit sucks! Few days back i ate up 15 bux (about 5 gallons ) in 49 miles LOL i wish my car got good gas. Maybe after a all gasket are changed w fuel filter, o2 and get some bosch supers i sould be good an my car feelin betta... i hate putting gas in everyday

[e30trooper]

I have an 89' 325is and I drive almost all city with occasional freeway usage an I get 200 miles on full tank. I do have a lead foot though.

i do the same , on it for 1,2,3rd gear only time i get good mpg is freeway

[funcrew]

something is not right in my e30
1989 325i 5speed
150 miles out of a full tank with 60% freeway driving 40 % street driving
running 91 octane
Jim Conforti chip
lowered on H&R cup kit
17X7.5 Kopi Alpinas
Hot air intake.

I had this symptom. Cured it by replacing odometer gears that had half the teeth missing. Doubled my gas mileage immediately.

[Dozyproductions]

on my 89' driving from San Diego to L.A, driving a full day in L.A, then going up to San Luis Obispo I'm at 380 miles. There is still some gas left so frankly I don't know how this car is doing it.

Had the tires pumped and always shifted at 3k rpm.

[robmespeedy]

in my old ETA i use to get an average of 315 miles per tank. 90% highway 10% street

[semiferger]

All the suggestions made are worth considering, they will have a positive effect. However, the easiest & cheapest way to better fuel economy is to change your driving habbits. I use my car daily for work (and keep a log book for miles driven and fuel used) and just by easing the amount of "go-pedal" applied, I'm getting more miles per tank. Less aggressive starts from a stand-still and doing 65mph on the freeway will yield improved numbers - for me about 60 to 65 more miles out of a tankful.

[Adrian_Visser]

All the suggestions made are worth considering, they will have a positive effect. However, the easiest & cheapest way to better fuel economy is to change your driving habbits. I use my car daily for work (and keep a log book for miles driven and fuel used) and just by easing the amount of "go-pedal" applied, I'm getting more miles per tank. Less aggressive starts from a stand-still and doing 65mph on the freeway will yield improved numbers - for me about 60 to 65 more miles out of a tankful.

Jon

All the suggestions made are worth considering, they will have a positive effect. However, the easiest & cheapest way to better fuel economy is to change your driving habbits. I use my car daily for work (and keep a log book for miles driven and fuel used) and just by easing the amount of "go-pedal" applied, I'm getting more miles per tank. Less aggressive starts from a stand-still and doing 65mph on the freeway will yield improved numbers - for me about 60 to 65 more miles out of a tankful.

Uhh were you trying to quote that or are you actually as unoriginal as to directly copy someone else's post in the same thread?

[ciscoboy]

I am shifting to a higher gear than is normally need, I shift to 5th gear at about 35. Seems to be yielding good results in my eta. I got 295 miles on my last tank of gas with a dragging caliper that I need to fix (ALOT of resistance).

Yes! Right on! This could be one thing most commonly overlooked.
I'd like to focus on non-engine related issues that cause poor gas mileage. These non-engine issues should be checked first. I've had problems with my brakes causing resistance and therefore resulting in loss of good gas mileage.
Mine is 1986 325e Automatic 210,000+ miles. I've always gotten 22mpg.
I agree, there is hundreds of things to look for when trying for better mpg.

This is the easiest no cost way to check for brake resistance:
Make sure car is cold and has been sitting for atleast overnight just to let brakes cool completely.
Jack one end of the car up and make sure its in neutral (if checking rear wheels) and turn your wheels by hand and check that they rotate easily and compare the resistance by feel. I found that you should be able to turn your rear wheels with one finger. If you have to use any more fingers then you definitely have to adjust your brake hardware or bleed the fluid lines.
Yes sir! Air in your calipers is causing a tiny amount of resistance and prematurely wearing your pads out.

I found that my emergency brakes were causing resistance. Not adjusting the emergency brakes correctly or precisely is one of the easiest things to screw up when changing your emergency breaks. And the hardware wasn't gliding easily because of rusty surfaces (sand where necessary)
I highly suggest always getting a new hardware kit when changing rear emergency brakes shoes. Of course all new brake discs and pads will definitely give you peace of mind.
Only heard great things about Seafoam. Gotta try it in my fuel.

To me these are the QUICKEST most important to get best mpg:
- most important of all is engine AIR FILTER
- DRIVING HABITS
- O2 sensor(s)
- type of TIRES (air pressure is most important then tire size-smaller diameter tires than original will yield more revolutions per mile and result in many less miles per gallon of fuel as is the same when driving on very worn tires.)
- SPARK PLUGS change twice a year- Its the cheapest insurance for your engine!
- GASOLINE octane rating- use higher octane 91 or 93
- OVERALL CLEANLINESS of emission and fuel components-definitely give Seafoam a try! Why the heck not? Anybody object?