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318is change differential for better MPG

I have a 1991 318is 5speed with a 4.10 LSD and 205/60 14 tires. I only get about 25 mpg highway and would like to get closer to 30. I do a lot of highway driving/ commuting, and would like to boost this while still maintaining good acceleration.

205/60 14's are not readily available any more. So the next set will probably be 195/70 14.

I have thought about changing the diff. to a 3.73 or lower for better MPG.

What is the lowest I could go to get better MPG and still maintain some acceleration around town?

Or should I just get taller tires?

Thoughts and Ideas please.

Keep in mind that E30 odometers aren't exactly accurate. You may want to try verifying this with a GPS unit.

I'd just let off the gas a bit. You WILL miss the 4.10.

You could even install a 2.93 out of a 325e, but you won't be happy with it.