Author Topic: Tips for Improving Mileage, Most of Which Simple (Read 36192 times)

oldtimer · « **Reply #120 on:** July 10, 2007, 06:05:32 AM »

I know replying with info particularly in this section of the forum someone will want to shoot me. but hey it's about improving mileages. I still don't know how all the combination of mod I have done to my 1984 318i is giving the the result of 29 mpg in the city and 35 mpg on the highway. Just maintained the car like they should be, induce "Seafoam" every 5k, oh yeah it runs on syntetic oil all 159k in the car. In addition to the seafoam treatment I clean the injectors the through the rail method. A wise tool investment for any "car carzy" person. MY 318is I still don't know what kind of mileage it gets being treated the same way. the "Odometer" is not working, gears are on order to fix. but I can't emagine it not getting the same if nor better mileage since treat the two cars the same. the only thing I have not managed to do on the "is" is advance the timing like the did with the 318i. Doing that made a major difference.

I do have one question for everyone. What is the difference with the 325i and 318i stock injectors? the reason I ask is. when the 318i was having some rpm issue I thought I would change out the injectors. A buddy had some 325i injector even though they were use I installed them in the 318i since that time the car started to get great mileage and some extra performance on the highway now doing 60mph I rarely have in the 5th gear the mileage meter indicates between 40 and 25 I think that's the range on the meter it's closer to the 40 side while doing 65 mph in 4th gear.

gearheadE30 · « **Reply #121 on:** July 10, 2007, 08:52:42 AM »

Sorry to get off topic again, but I just replaced the oil in my engine, with 200k on it, with 10w40 synthetic, and there are no leaks at all and the engine is quieter. Not much of a performance difference, though.

Alpine003 · « **Reply #122 on:** July 10, 2007, 11:08:03 AM »

Quote from: oldtimer;29350

the only thing I have not managed to do on the "is" is advance the timing like the did with the 318i. Doing that made a major difference.

We have distributorless ignition so it's a lot harder to advance the ignition on the M42 engine vs. m10.

christophbmw · « **Reply #123 on:** July 14, 2007, 11:45:57 AM »

quick question, what size tires is everybody running i relation to gas milage? i am running 205/55-15's. 3600-3700rpm at 80 on the freeway.

sheepdog · « **Reply #124 on:** July 14, 2007, 11:50:28 AM »

195/60-14

The RPM's will probably not be different by more than one or two hundred rpms unless you have a massive tire or gearing change.

tjts1 · « **Reply #125 on:** July 14, 2007, 12:19:21 PM »

My car came with different size tires front and rear. 195/60R14 in the front and 195/65R14 in the rear. The 195/60 is 3.2% smaller so I keep those in the front.

318/6 · « **Reply #126 on:** August 09, 2009, 05:29:45 PM »

In an effort to maximize fuel efficiency while keeping performance relatively high, we made a few adjustments to our 318is.

Engine build:
Rebuilt bottomend using 86mm slugs from '95 M3
Machined valve cutouts to drop static c/r slightly in order to use 87oct
Special rods to save rotating mass of over 900 grams
All pistons and rods balanced to within .25g
Very loosely built bottomend
Intake cam advanced xx-degrees
12 pound flywheel (soon to be swapped to 7 pound unit)
stock 4.10 gearing for now, s3.91 in the garage
Weight: 2460 with full stock trim and full tank
Fuel economy over 975 miles: 3 passengers and a loaded trunk -- 37mpg @ 74-76mph.
Should do 40mpg easily running solo. Oh yea, and it's as fast as a 25i.

longtallsally · « **Reply #127 on:** February 15, 2010, 02:03:23 AM »

I want to revive this one. For my latest E30 I chose the M42 due to weight distribution and fuel economy.

However, I just checked and on my last tank, I got 20 avg. Kinda pathetic. 185k on the clock and nothing but fluid changes to full synthetic front to rear.

There are some really good ideas here and as I wait for the arrival of my tools, some good food for thought.

For the instant improvements I need to check TPs, going to check the O2 sensor, air filter, and spark plugs.

I did have a question; will cleaning out the intake manifold help at all? I thought I read that the are notorious for getting gummed up?

///m42 sport · « **Reply #128 on:** March 14, 2010, 05:16:25 PM »

Quote from: tjts1;29317

One thing I didn't have on the car for this trip was a lower front air dam. I think an IS type air dam would reduce drag. Maybe next time.

I think your right. I've seen my mpg go down w/o the IS lip.

So is there hope of seeing 35+ mpg on highways?

BlueBMW · « **Reply #129 on:** March 14, 2010, 05:52:16 PM »

I noticed that a lot of new BMWs have full underbody paneling to supposedly improve airflow under the car. Would some sort of custom fabricated underbody plastic pan possibly improve economy on these cars?

tjts1 · « **Reply #130 on:** March 14, 2010, 06:07:02 PM »

Quote from: ///m42 sport;89474

I think your right. I've seen my mpg go down w/o the IS lip.

So is there hope of seeing 35+ mpg on highways?

Yes. Volvo lip helped a lot. I have seen 35mpg on 87 octane since.

Quote from: BlueBMW;89475

I noticed that a lot of new BMWs have full underbody paneling to supposedly improve airflow under the car. Would some sort of custom fabricated underbody plastic pan possibly improve economy on these cars?

I haven't tried it on the bmw but it helped on my volvo. I used coroplast.
http://ecomodder.com/forum/showthread.php/volvo-850-coroplast-wonder-4093.html

///m42 sport · « **Reply #131 on:** March 14, 2010, 07:21:17 PM »

thats a pretty cool website. Maybe you should start a thread on building a "green" 318is?

longtallsally · « **Reply #132 on:** October 21, 2010, 03:45:55 AM »

So I have a new tip: DON'T DRIVE IN STOP AND GO TRAFFIC!!!!! I'm sure no one wants to, but MAN does it make a difference. I lost 3 mpg without batting an eye on a tank by sitting in traffic for only a couple trips.

tjts1, did that stuff on the underbody ever really garner some good results? For reference, my wife's E46 325xi will get 30 mpg at around 70 mph and the underside is almost as smooth as on top...

DesktopDave · « **Reply #133 on:** October 21, 2010, 08:11:16 AM »

Any stop and go will cut into mileage. If I'm going to be stopped for more than 2 minutes I shut the motor off. Likely I won't save enough gas to buy a starter, but it's worth it to me. These motors are not very efficient in urban/suburban stop & go driving. Highway is far better, I'm not sure why.

My biggest bump in efficiency was fitting cruise control - made more difference than type of gasoline, tire size or drafting semis. I haven't run the numbers in a few months, but I'll bet it gave me 10%.

Things that have helped:
Cruise control
Driving like Granny
Closed windows no A/C
Full synthetic 5w20 or 5w30 motor oil, full synthetic ATF in the gearbox, full synthetic 70w90 in the diff.
Avoiding gasoline with more than 10% ethanol (in PA they're forced to label >10%)
Leave the throttle body heater
3.73 diff

The things I'm planning to bump up economy:
Warmer thermostat & aux rad fanstat
Delete clutch fan & add electric
WBO2 to monitor mixture
Underbody pan & more front spoiler
Seal or minimize body seams
Slightly taller & skinnier all season tires
Take warm air from engine compartment instead of front facia

///m42 sport · « **Reply #134 on:** October 31, 2010, 05:11:19 PM »

^^Does fuel economy improve with cruise control or without? I've noticed the opposite.

I've noticed that on highway cruising at 65 with the cruise control, and 410lsd, I get about 26mpg on the obc. But if I turn it off I can get somewhat better mpg.

Anyone else notice this?