I have not had any problems with the OVP Relay yet and am currently getting 22-23 in town and back and forth to work
(rural driving < 60MPH) and 26 on the Hwy @ 75-80MPH. My E
has 143K on it and still running good. It is starting to take a little longer to start after it sits for a few days
so I believe that I may need to replace the check valve in the fuel pump. Still the original OVP though. I have been using Mid grade fuel 89 oct and it runs the same as it did on Premium 91 oct.

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Dave
88 300E 250K Sold
2000 C230K Totaled @104K
2003 ML320 156K Sold
2009 E350 4Matic Sport 46K Sold
2011 ML350 60K Sold
2014 GLK350 46k
2012 GL450 55K