Recently acquired a classic 1972 Mercedes 280SE 4.5, and while initial inspections were promising, some new concerns have emerged shortly after routine maintenance. After purchasing my ’72 Mercedes, it passed the Virginia inspection, though a tire replacement was recommended. Following this, I took the car to a national chain for two new front tires and a full check-up, including fluid changes. Initially, things seemed fine, but now I’m experiencing a couple of worrying issues.
The first problem is a noticeable increase in engine noise. It’s not a harsh clanking sound of metal on metal, but more of a pronounced, almost helicopter-like whirring. Secondly, and perhaps more concerning, the oil pressure gauge is behaving erratically. Before these issues arose, the oil pressure would sit at about a third of the gauge at idle, and shoot right to the top when accelerating. Now, at idle, the oil pressure barely registers, hovering near zero, and only climbs to about halfway up the gauge when the accelerator is pressed.
Seeking advice, I contacted Dan Pool Mercedes here in Northern Virginia. The service advisor immediately inquired about the oil weight used in the recent service. A quick call back to the tire and battery chain confirmed they had used 5W30 oil. Upon relaying this information to Dan Pool Mercedes, the advisor expressed surprise, stating that 15W40 is the correct viscosity for this engine.
Consulting the owner’s manual for my ’72 Mercedes 280SE 4.5, it specifies “Year-round use multigrade oil, 10-w-40, 10-w-50.” It’s clear the national chain used an oil grade significantly lighter than recommended, and different from what a Mercedes specialist suggests.
Now, the question is: should I strictly adhere to the manual’s recommendation of 10W-40 or 10W-50, or follow the 15W40 suggestion from the experienced Mercedes mechanic? Any insights or recommendations regarding the best oil for my ’72 Mercedes 280SE 4.5, and whether this incorrect oil viscosity could be the cause of the engine noise and oil pressure fluctuations, would be greatly appreciated.
