Subject: [Mgs] Oil viscosity for 3.5 V8 engine

From: <[email-masked]>
Date: Fri, 7 Oct 2022 11:02:23 -0400

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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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class=3DWordSection1><p class=3DMsoNormal><span =
style=3D'font-size:12.0pt'>I am puzzled about the proper oil viscosity =
for my Rover 3.5 V8 engine. Des Hammill's book <i>How to Power Tune RV8 =
Engines </i>states &#8220;Anyone used to oil pressures hovering around =
70 &#8211; 75 psi on an MGB 1800 engine will be alarmed to see pressures =
in the Rover V8 reading 15 &#8211; 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.&#8221; &nbsp;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?<o:p></o:p></span></p><p class=3DMsoNormal><span =
style=3D'font-size:12.0pt'><o:p>&nbsp;</o:p></span></p><p =
class=3DMsoNormal><span style=3D'font-size:12.0pt'>Thanks in advance for =
your input.<o:p></o:p></span></p><p class=3DMsoNormal><span =
style=3D'font-size:12.0pt'><o:p>&nbsp;</o:p></span></p><p =
class=3DMsoNormal><span style=3D'font-size:12.0pt'>Jim =
Ray<o:p></o:p></span></p></div></body></html>
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From: PaulHunt73 <[email-masked]> ITJa//ebhoBvXrEWP35vy3E1kSWxsuzwyxDnpHSLqsJvHMzhQYzjmqDhm1xL2UwAKHzKzVKCNjglbakPkVppCpBlTwflYeQT9Nc=
Date: Sat, 8 Oct 2022 08:51:31 +0100

As Hammill says the Rover V8 engine is a low pressure, high flow engine 
because of the additional places for oil to exit pressurised areas and 
get back to the sump not least the hydraulic tappets.  The pressures 
quoted are optimal if not optimistic, you can get a lot lower hot idle 
than that on older engines - barely registering on the gauge.  It 
depends on what you mean by 15W 50 being 'a bit high', the factory 
specified the same oil viscosities for the V8 as it did for the 
4-cylinder, i.e. for all temperatures above -10 C (10F) 10W 40 being the 
minimum and 20W 50 the maximum.  Because the lower viscosities do result 
in lower pressures I've always run 20W 50 in mine which is on its third 
time round the clock, albeit with a rebore and regrind a couple of years 
ago.

You can't compare it with oil for modern cars, which can cause harm in 
our engines.

PaulH.

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