best diff for economy

[lamby]

i use my 88 320 auto on motorways a lot and need to know what ratio would be best to drop the revs improving economy,i dont boot it,and its a standard box no sport option

[Sanchez]

320i auto is probably the worst e30 engine box combo for MPG ive heard.

but for better mpg lowering the ratio eg 4.27 to a 3.64 diff would help mpg but not performance.

Check the e30zone wiki, full of info.

[bimanut]

3.64 should do you right but i thought that is the ratio fitted to your car.
Reason i say this is that i removed a 3.64 from a 320 a few months ago.
Didnt notice if manual or auto tho

[Sanchez]

should have a 4.10 fited.

[lamby]

i,ll see if theres any markings on it,yes i know it,s prob worst combo but it was the right colour etc,it,s doing 30 odd at 70 and 37 at 60 but you need to be at 70 at least nowadays