I recently bought a 1998 V70 with manual trans. It is the base version without the MPG trip computer function in the instrument cluster. Here is what I have learned about adding the MPG function on 850s and V70s:

1. Pre 1996 850s have mechanical odometers. In the instrument cluster, the trip computer with MPG function requires a different module from the one that only provides time and temperature. MPG function can be added by replacing the module and adding the Info switch in the dashboard.

2. 1996-1997 850s have instrument clusters with mechanical odometers. I think the clusters are compatible with 1998 V70 clusters that have digital odometers. On the volvospeed forum I read about someone who replaced a 1997 850 cluster with a V70 1998 cluster and it plugged in with no problem. Not sure how to add MPG function on 1996-1997 850.

3. 1998 V70 instrument clusters have digital odometers. The trip computer MPG function is already built into the cluster but has to be activated through the OBD2 connector by a Volvo dealer. The activation information is stored in the instrument cluster, not the ECU.

4. 1999-2000 V70 instrument clusters are not compatible with 1998, probably because the 1999-2000 engines have an Electronic Throttle Body instead of mechanical like the 1994-1997 850s and 1998 V70. Adding the trip computer MPG function on a 1999-2000 V70 requires a software change in the ECU, not just the instrument cluster.

Can anyone confirm that there are 2 ways to add the trip computer MPG function to my 1998 base V70 (assuming I add the Info switch to the dashboard):

1. Find a Volvo dealer that will enable the trip computer MPG functions in the existing instrument cluster.

2. Replace the existing instrument cluster with a 1998 V70 cluster that already has the MPG function activated.

Thanks,

Mike