I have a 2006 DT466 7.6L shuttle bus that my church and daughter's BBall team uses all the time. We seem to be losing a massive amount of oil (1 gallon every 500 miles) on recent trips. Took to Int'l dealer, said there was a crack in the oil cooler gasket and oil cooler itself. Replaced, and oil pressure held for two trips. Now we are back to losing lots of oil. It is NOT burning oil at all, we steamed the engine and there is no VISIBLE oil spewing out of the engine during high rev idling. There is also no visible leaking of oil around the rear main seal. The one thing that is visible, is that the ENTIRE undercarriage has oil all over it. It appears to be coming out of the vent tube however sitting still we cannot duplicate the problem. Only when we get the bus up to 65-70mph does the oil loss occur............PLEASE HELP US!!