gas milage

[viali8]

hello all,
I have an 87 325 with 216,xxx miles. just recently i have a seen a drastic drop in my gas milage. When i first bought the car i was getting about 260-270 miles per tank in the city and 340-350 on the highway. Now i am only getting about 260 miles to the tank on the highway.
I changed the fuel filter about 40,000 miles ago. What could it be that is giving me such poor gas milage? Also i bought the car with 177,xxx miles but never changed the O 2 sensor. Could that be the problem?
Has anyone had the same problem before and what did u do to fix it? Oh also i am driving with snow tires on the back, but i doubt that makes not much of a difference.

[///M42 sport]

I think you answered your own question. Are there any other symptoms, like hestitating or rough idle?

[viali8]

gas milage

1.) When it was really cold out the idle would go up and down. I really wouldn't call it rough though. in between 600-900 rpms. Now it idles fine.
2.) Yes there is some hesitating but only when i acceleratefrom a stop. other then that the car runs great. but i think the hesitation is due to me putting in platinum spark plugs. (i know, big mistake)

[Drewe30e]

1.) When it was really cold out the idle would go up and down. I really wouldn't call it rough though. in between 600-900 rpms. Now it idles fine.
2.) Yes there is some hesitating but only when i acceleratefrom a stop. other then that the car runs great. but i think the hesitation is due to me putting in platinum spark plugs. (i know, big mistake)

Just curious, why is it a big mistake to put platinum plugs in?

[viali8]

gas milage

just from reading throught the forums, people say not to put platinum plugs in you e30. i guess they are too hot. there is a funny picture someone has here on the forums, its a ca with machine gun and the cat says, don't use platinums in your bmw it's not a ford.

[kowalski]

your supposed to use bosche supers. many people have problems with platinums causing loapy idle. some don't, but its just best not to find out as you wont see any gains from them.

[EtaSport]

platinum plugs are a waist of money IMO, as well as those iridium plugs for non turbo applications. The heat range of the plug usually isnt determined by the conductive material.

If your car has a bad o2 sensor it should throw a CEL. This is true for most other fuel injection related sensors when they go bad. I would consider replacing plugs, wires, cap and rotor if they havent been done that you know of. Other than that, FPR can cause high fuel consumption if its faulty. Easy way to check is hook a fuel pressure gauge in line with the feed line, then unplug the vacuum line to the FPR and look for an increase in pressure, if there is one, then the unit is fine. If no, replace.