325is Mileage question

[aTron12]

My 1989 325is, M20-manual trans with a 4.10 LSD gets about 250 miles per tank. The car is lowered (eibach) but not slammed so the camber is slightly off but not extreme. I also went 205 on my 14" tire width..

I remember my totally stock (4.10 open diff) M20 Alpine White automatic used to push 275 miles per tank. With the price of gas shooting up (fuckers) I would appreciate some input on where to start looking before taking it to my mechanic.

What are you guys getting per tank? I am about half street/half highway and keep it under 80mph.

Thanks!

Adam

[blefevre]

I get 25-26mpg in my 90 325is with a 4.10 LSD and 225 wide tires. Not sure what that equals in miles per tank as I never run it near empty.

[nando]

25-26 is over 300 miles per tank, and is fairly normal for a B25 in good running condition on the highway.

250 miles per tank is about 17mpg. you should be able to average at least around 300 miles/21mpg.

I'm assuming you're running it down to the light which is where you hit the reserve capacity of about 2 gallons (thus the "R" instead of an "E").

[aTron12]

Yes, I do run it down to the light. Usually refill as soon as the gas gauge light comes on. I do use 91 gas, of course.

The car is in fantastic running condition.. all new vacuum lines/hoses, rebuilt head, new clutch/driveshaft, cooling system is new. Newer plugs (they are clean. Checked em out recently), plug wires and Dist. cap. Change oil and filter regularly. Use Mobil 1 15-50. Water pump, timing belt, all new suspension.

It's going into the shop tomorrow for this as well as a few other little things so I'll mention the gas mileage to him. Thanks for the input.

[blefevre]

Have you checked if your odo reads mileage correctly?

[mr.vang]

change the fuel filter yet? get small tires, make sure air filter is not clog and make sure it have the right amount of air in the tires.

[nando]

205 width tires are not going to make an E30 get 17mpg

[blefevre]

The only other thing not listed already is fuel injectors. Check them out or send them out to get cleaned/tested.

[Cabriolet]

i have a 4.10 LSD, dinan chip, if i drive careful on the freeway is get 22.5mpg. if i drive like an idiot on the streets i get 7-9mpg. ~i get 230 miles/ 14 gal. = 16.5 mpg.

[MTechnikII]

check the valve adjustment, Bently's recomended clearance was the reason for low MPG on my car, go about 0.005 over what bently recomends, as soon as I increased the clearance the MPG went from 10 , 11 to 18, 19 average( normal driving, occasionally drops due to my lead foot)
before the valve readjustment I replaced what ever was replacebale to get the MPG up but nothing worked.
91 325i convertible, 210 kmiles auto, always used Mobil1 10w30 carring extra weight of 2 e36 power seats all the time, ( I think they weigh 80Lbs each)
Henry

[aTron12]

New fuel and air filter also. Interesting about the valves. My car has 230k and probably original injectors. Maybe they are gunked up? I've used Jectron via gas tank a few times but haven't had them professionally purged.

[Jargo]

My bet would be the old, clogged injectors. Also, even though you have new plugs I would check the gap on all of them. The last set I bought were very inconsistent, some tight, some loose. Also you say you run synthetic in the motor, fresh synthetic in trans and diff always helps me gain a few mpg. And for maximum economy, keep it under 60mph. Haha yeah right!

[aTron12]

I have two mechanics. One guy is at German Auto Sport in Berkeley (they rule btw) and the other has his own private business restoring old E9 coupes and E23 745i. My E30 has been his exception . So the guy at German Auto couldn't find anything that would be effecting my fuel economy so the basics are taken care of. My other mechanic says that I should be looking into fuel injectors which backed up what Blefevre and Jargo were sayin'. I went down to the yard and pulled 6 injectors and dropped them off to be purged and restored. Let's hope that helps!

Also, I popped open my Motronic for the first time today and found an eBay chip installed. I had a hunch that something was going on there. Does anyone know if these chips effect mileage? I gotta say, there was a noticeable difference with the chip out. Less tourque... If another chip goes in, I am going BavAuto or Jim C. So any opinions on if the chip could be contributing to my 10MPG loss??

Adam

[riceh8r]

what octane gas are you using?? just read you use 91, good deal.

[aTron12]

I'm driving about 75mph on the highway. That shouldn't reduce it that much right?