[Mgs] Oil viscosity for 3.5 V8 engine

Max Heim mvheim at sonic.net
Fri Oct 7 16:53:06 MDT 2022

I am using 15W50 in all my cars at this point: 1966 MGB, 1967 Plymouth slant six, 1967 Plymouth 4bbl V8; specifically, Mobil1 15W50 which is formulated for flat tappet engines and has 1500ppm zinc. Note that other weights of this brand are NOT appropriate for older cars.

50 is not too high viscosity for summer use in California (it’s really what you want), and 15W indicates that is not too heavy for winter use.

Max Heim
'66 MGB

> On Oct 7, 2022, at 8:02 AM, <jimray at hartcom.net> <jimray at hartcom.net> wrote:
> I am puzzled about the proper oil viscosity for my Rover 3.5 V8 engine. Des Hammill's book How to Power Tune RV8 Engines states “Anyone used to oil pressures hovering around 70 – 75 psi on an MGB 1800 engine will be alarmed to see pressures in the Rover V8 reading 15 – 40 psi. These engines are low-pressure engines with normal pressures (hot) at 20 psi idle using a 15W 50 oil, and 40 psi over about 3500 rpm.”  Its time for me to change the oil in mine and 15W 50 seems a bit high when compared to oil normally used in my other US built cars. Anyone have any thoughts or suggestions to this?
> Thanks in advance for your input.
> Jim Ray
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