VRO means Variable Rate Oil Injection...which is really a misnomer for the pumps today. The original intent of these pumps was to vary the oil mix at different speeds/rpms. The pumps of today just mix the oil at 50:1...so...the name of today is Oil Metering System. The VRO monicker just stuck.<br /><br />No it will not hurt to run the engine with 50:1 mix and the "VRO"...there is goes again... It is recommended in the service manuals that this be done until oil usage is confirmed. If your worried about the carbon build up, use a synthetic blend or all synthetic TCW-3 oil. Or just do a decarb after the test period.