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Fuel economy 325 E30's

4989 Views 12 Replies 8 Participants Last post by  tdennehy
I have seen a lot of posts for performance parts but little on fuel efficiency. Does anyone know if there is any modification to change the gear ratios on the final drive or manual transmission to enhance fuel economy? I have seen some posts claiming that some of the M3's have done modifications that have taken them into the 40mpg range. I would think a 6th gear overdrive with a smaller final drive ratio would allow a high top end speed with less rpm's. Yet, still would have the lower gear speed for winding alpine driving. With the price of gas rising I would like our 87 325 to get a little better. When tuned and everything new (timing belt, coil, plugs, wires, oxygen sensor and canister) we see as high as 32 mpg with just highway. This is with cruise set at about 70 (found out that at 70 on speedometer we were only doing about 67). Around town and highway, we get about 23 to 25. If we push the car to 80 or faster, we get about 21 to 24 on the highway. Curious to hear other comparisons and thoughts.
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fuel economy in your e30

I had an '86 325es, and she got 32 MPG. Now I drive a 1990 325iC, and she gets 25 MPG. I'm wondering how I can get that kind of mileage in my "new" car...

Did you do anything special to your car?

I have seen a lot of posts for performance parts but little on fuel efficiency. Does anyone know if there is any modification to change the gear ratios on the final drive or manual transmission to enhance fuel economy? I have seen some posts claiming that some of the M3's have done modifications that have taken them into the 40mpg range. I would think a 6th gear overdrive with a smaller final drive ratio would allow a high top end speed with less rpm's. Yet, still would have the lower gear speed for winding alpine driving. With the price of gas rising I would like our 87 325 to get a little better. When tuned and everything new (timing belt, coil, plugs, wires, oxygen sensor and canister) we see as high as 32 mpg with just highway. This is with cruise set at about 70 (found out that at 70 on speedometer we were only doing about 67). Around town and highway, we get about 23 to 25. If we push the car to 80 or faster, we get about 21 to 24 on the highway. Curious to hear other comparisons and thoughts.
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fuel efficiency

I think I am going to take your advice and empty out the car and make sure I have the right amount of air pressure in my tires.

I think the only modification I could ever do would be swap out the rear differential. But I would want to drive a car like mine that has already had the work done so I know what to expect.

The other thing is how much money would I actually save? If I drive 12,500 miles per year, and am able to do something to my car to increase from 25 mpg to 30 mpg, I will save $292 dollars annually.

The return of investment for swapping out the rear end would take two years if I paid 600 dollars to get the job done. It might not be worth it.

Not sure if there are "fuel efficient tires" out there, but if there were, I would buy them when the time comes to replace the existing ones.

I'm impressed that you were able to fit a V-12 inside your car. That car must FLY!!!
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e30 fuel economy

Sadly, we Americans drive 25+ miles to work each way, and many people drive 50 miles each way.

I love how the e30 feels when zipping down the highway at 70 mph. And since I paid cash for the car, I want to get my money's worth out of her. And I just love the old Bimmer look. I would buy another just to have as a spare if I could fine one that I liked!

I take every tax advantage I can legitimately take, and mileage just isn't one of them. I figured that if I could increase my MPG to 30 from 25, I would save 300 dollars a year in fuel. Since you are an account, I don't need to say anything more about those numbers... buying a new car just won't give me a return on the investment.

Did I mention I love driving an e30? :)

My next set of tires will be the fuel efficient type.
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15-17 mpg

Dang! That is pretty poor fuel economy. Guess I will quit complaining...
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