gas milages

[garyh]

hey guys i got 01 330i, i get about 300miles of every tank and i think thats pretty bad fuel economy and im running 91oct, the reason im running 91 oct is cuz first it says on gas cap.... second week after i bought that car 3 of the fuel injectors were leaking and spraying fuel out, and i think once i filled it with 89 or 87oct so im guessing that might have caused it im scared to run 87 or 89 now cuz what if the gas wrecks the injectors again and they aint cheap 1000 for 6. help me out

[Manolito]

I presume that you are putting in about 15 gallons every time you fill up, right?

That works out to 20 mpg, which is OK for stoplight driving but not so good for road trips on the freeway. On the freeway, at 70 mph, you should be at 26-27 mpg.

Low octane fuel will not hurt your injectors, but low quality fuel might. If you buying at some independent like Horrible Harry's Cheap Gas, you can get some interesting stuff blended into the fuel.

With regard to octane, our 330 is not as tolerant of low octane fuel as our two '97 328s. The car has to retard its timing to keep from pinging on lower octane fuel. On the '97s, they make a couple less horses, but run perfectly. On the '04 330, it seems to really affect performance.

If you ever again have injector problems, pull them out and mail them somewhere like Cruzin Performance or Witchhunter to be cleaned. These injectors rarely fail such that a cleaning won't put them right, and in the event that one or two need to be replaced, the cleaning service will flag them for you and tell you what is wrong with them.

Check how much alcohol (probably ethanol) is in your winter fuel, and see what BMW says about burning that kind of alcohol, to make sure it is OK for the fuel system. Winter fuel with alcohol in it has less energy per gallon, so you will get a slight hit in fuel economy in winter.

If you are getting only 20 mpg on the open highway, there is a problem. Air filter clean? No exhaust obstruction? (you should be able to feel the individual bursts of exhaust at your muffler outlet) How old are your oxygen sensors? They are only good for about 100k miles, but usually the computer starts complaining about them before they really hurt the gas mileage.

[garyh]

i only get gas from chevron or esso, heard gud stories about them so obiviously not cheap as gas places and actually i forgot to mention i had the check engine light on scanned it and it said something about o2 heater i know that will effect for sure, so ur saying i should stick with 91 oct gas? mines 2001, has about 98000 miles on it replaced spark plugs day or two ago. r u gud with bmw m54 engines

[Manolito]

The heater is intended to get the oxygen sensor working as soon as possible after you start the car. However, on my 4 cyl Volvo, when I had a problem with the circuit to the heater, under light load, my sensor would cool down enough to stop working properly and set a check engine light.

If your senser is too cool to work, or if the sensor heater code is a 'hard failure' code that causes the computer to ignore the readings it is getting from the sensor and go into 'limp home' mode, that will cause your gas mileage to drop off substantially.

A heater failure is probably in the sensor, but in my Volvo it wasn't, so I would:
1) Check the power line to the oxygen sensor heater at the plug (under the plastic cover on top of your engine I think and make sure you have power there.
2) If you have power to your heaters, then you are looking at another expense, because the next step is new oxygen sensors. You could replace just one, but at 98k mi, I would do them as a matched set. The good news is that the price of sensors has come down since Bosch moved their operations to the middle east and the other vendors have matched the new lower price. They are still over $100 each. I presume there are 4 on an e46 like there are on an e36. I have not done an e46, but on other BMWs, all you need is an end wrench and a 10mm socket and a pair of ramps to replace them. Do them one at a time so you don't cross the wires! The wires are strung so that they come out different lengths so it is hard to cross them, but it would be a bugger if you did cross them because the car would not run well and it would be tough to figure out why.

[garyh]

yeah i think ima replace pre cat sensors cuz post cat sensors barely fail and im being lil on cheap side as well so ima prolly go with set of 2 pre cat. and i think ima put amc cold intak, that should help too, thinking about lowering it got quote on h&r adjustble set for all wheels asking about 1550, what do u thnk of h&r?? or anything else u can recommend?

[Manolito]

A cold intake will not improve gas mileage. You may pick up a little better power at high RPM at the expense of having more intake noise all the time. On an e36, you get the same benefit by simply cutting the silencer baffle out of the air box. I have never looked at an e46 air box to see how it is designed. I advise against oiled permanent air filters which are often used on aftermarket air intake systems.

I know nothing of lowering because that is not something that I would ever consider doing to an e46. They have very little ground clearance as it is.

My advice - start with a nice clean car. Put on nice 17" wheels (no larger) if it did not come with nice wheels. Keep it clean and protected inside and out. Keep it mechanically as perfect as you can. Enjoy it. Don't waste money on things that shorten the life of the car and result in future expenses without really improving the performance of the car.

When you are looking for tires, I love my Michelin Pilot Sport All Season tires. They are much quieter and smoother than the Continentals that came on the car, and they seem to be holding up very well. They look good good on the 17" M wheels.

[garyh]

hey man sry was away for couple days, ya i heard bad stories about after market filters, my car came with shitty wheels i just wana make it bit eye catcher, the exterior color is white i wana put 19" black with white lip, n lower it down, thats about it n obiviously tint/lights.

[garyh]

yo got anotha question when i put in gear at idle i hear this rattle/vibration on front dash kinda toward passanger side, any idea? plus underhood its bit noisy too rattle/vibration.
are those plastic intake noisy???

[Manolito]

Never dealt with rattles on my e46, but on cars in general, rattles in the dash result from:

1) Small objects dropped down into windshield vents or poked into air conditioning vents by small children.
2) Underdash pieces that were removed and not properly reassembled by a previous owner during a repair.

Rattles under the hood are usually:
1) Worn bearings on serpentine belt tensioners.
2) Loose or cracked heat shrouds
3) Missing hardware on heat shrouds or other covers
4) A cracked exhaust manifold or leaking header pipe can sound like a rattle sometimes.
5) Worn bearings on alternator or air conditioner.

The worn bearing noises are more of a chatter than a rattle.


19" wheels are are fashionable, but awfully big. I suspect that some day you will look back at a picture of the car and ask yourself "What was I thinking?" Did I understand that you want black wheels with white lips? You might want to photoshop those onto a picture of your car before you lay down your money.

[garyh]

i meant black wheels with chrome lip, i'll have someone drive my car so i can try to diagnose the rattle so i can trace it down, yeah i know what u mean man but dude gota pimp rides out though, ima give it shot, at least i wont feel that i wish i would have done that when i was young

[Manolito]

Go for it. Buying pimp wheels is far more prudent than what I did when I was your age. I worked a dangerous job because it would pay for my expensive hobbies that included drag racing motorcycles, sky diving, hang gliding, and consuming various pharmaceuticals. 30 years later, all I have to show for all that money earned and spent is a lot of scars, some joints that don't bend, and some herniated disks in my back.