Gary E Steele
i have a 2006, same issue but had a head gasket issue as to why i went into it. i have the 3.5 i VTEC. i believe the oil varnish staining is due to a poor engine design. if you also look you will notice the exhaust recirc porting for smog is on the fwd head only (more retained heat). the varnishing is due to the excessive heat and yes only on the fwd head because the rear 3 cylinders are shut down (or nearly) at freeway speeds to improve gas mileage leaving the engine to run off the fwd 3 cylinders, hence the fwd bank has more load and runs hotter. on mine, it was the fwd head that warped causing the loss of water and yes on the exhaust recirc end and had to replace the fwd cam also due to pitting on the intake lobes, i believe all heat related over time and not due to the loss of water. that was at 160,000. probably other issues related but that is my 2 cents.