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Al Eckstadt
Al Eckstadt
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Hi folks
Thinking about changing the rev counter for an electric one. The one I’m looking at comes with the option of an engine oil temperature display and sender unit.
Just wondering if anyone on the site has done this with Oil-In-Frame models.
Having just had an SRM conversion and engine rebuild, and run in with a 20-50 mineral oil, it’s time for an oil change, and thinking what’s best to use.
A multi-grade oil needs to achieve a minimum temperature of 100c / 212f to reach it’s working viscosity, and I’m wondering as the oil flows through the frame (which is kind of acting as a large heat sink), how much the cooling effect changes the viscosity of the oil, also the longevity of the oil, especially in cooler climates.
The alternative is to use a straight 40 or straight 50, which would not be affected by the cooling effect of the frame. The downside is of course poor circulation at cold starting, plus they’re mostly basic mineral low-detergent oils. All the Esters, Synthetic and Semi-synthetics seem to be multi-grades now. (I would avoid Castrol R)

Any thoughts?

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I run Eater based 20/50 with no problems (Fuchs Comp 4) I used to run the 10/40 again without any issues.

With any oil I’ve used on my Pre oif the oil in the tank has always been between 40-48°c on a red hot day. The stress on the oil is when it’s under sheer stress (ie passing the big ends) and the heat, so when it’s cold it’s not exceeding its limitations. And on a cold day the warmth of the engine will quickly heat the oil as it’s passing through, just as the oil will attempt to cool the engine.

It’s ability to not cool sufficiently on a hot day when your problems start.


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (now rebuilt)
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Hi Allan.
Thanks for your reply. I'd bought some Motul Ester 15-50, then wondered if a straight 40 or 50 might be better. But I think you're right when you say the heat of the engine will quickly brink the oil up to temperature, and help to cool the engine in the process. Perhaps you can over-think these things sometimes!


The next thing to think about is whether to fit an external oil filter.

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Don't think about it, as Nike used to say "just do it"!

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Perhaps you can over-think these things sometimes!

Put some oil in and ride it.
It's an A65 !!

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I run 20/50 , max oil temps I recorded are 54 C with an IR thermometer shining in the filler after a good thrash ambient around 20 C. It gets hotter in the motor, dont over think it.
Do fit an external filter in the return line, my set up. Plug the small line which feeds the rockers from the manifold, put a T in the line after the filter, feed the rockers from the T. If you dont there is a tendency to bypass the filter and over oil the top with hot return oil which doesnt get filtered. ive tried both ways, the T after the filter works better.
The filter adds useful oil volume, the book states oil capacity as 5 1/2 pints, this is a lie, the spine only holds around 3 pints, maybe another 1/2 pint or so in the lines and sump.


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Just wondering how many miles have been covered during the run in and what type of rings have been fitted?

Personally I would stick with mineral 20W50 with plenty of zinc for the first couple of thousand miles as this will help the rings bed in, especially if they are the plain cast iron types. If there is any evidence of smoke in the exhaust then the rings probably arent fully seated yet and a synthetic oil wont help.

Using an oil filter is essential on these engines so is recommended as is using an alloy sump plate with magnetic filter.

Agree with the other comments about oil temp and the oil in my pre OIF A65 never seems to get any warmer than whats already been mentioned. However I expect that inside the engine it gets above 100c in certain areas.


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Thanks for all the replies, much appreciated.
Already got a spin-on filter, just need to mount it somewhere. Gavin, thanks for the tip about teeing off after the filter for the rockers. Good idea.
Just a shame about the weather!

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Rodger "A multi-grade oil needs to achieve a minimum temperature of 100c / 212f to reach it’s working viscosity"

where did u get that info it doesnt sound right to me ?

I run a straight 50 on my 70 (not OIF but i dont see tat making a lot of difference. It loves the 50 and runs quieter and leakages are almost arid ...but having said that our winters arnt as arctic as UK and im too lazy to do season oil changes


"There's the way it ought to be and there's the way it is" (Sgt Barnes)

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