Oils

[nickspeed]

Any suggestions on engine, gearbox and diff oils? Have previously used what I think was Redline, a lightweight shockproof oil, in the transaxle of a sporting trials car. Very ‘thin’, making for low drag but with good protection. Would this be appropriate for the gearbox and diff? then maybe a 20/60 for the engine? With thanks, Nick

[rgh0]

A top quality full synthetic 10W/50 for the engine. Redline MTL for the Gear box and Redline 75W/90 Gear oil for the diff

A long discussion on oils here

viewtopic.php?f=37&t=42119&start=

cheers
Rohan

[nickspeed]

Brilliant. Thank you Rohan! Cheers, Nick

[JonB]

Just to add to this - Rohan, what would you suggest for a "running in" oil for a rebuilt engine?

[512BB]

You don't need a running in oil Jon. Just a budget 20 / 50 oil for the first 500 miles, then a quality oil after that. Some use synthetic, I use old stock Castrol or Duckhams 20 / 50. Why? Because that is what they were designed to use. You know it makes sense.

And don't let the engine sit idling for hours, you will glaze the bores. Get out there on the road and give it some beans, after it is up to temps of course.

Leslie

[sng]

I have read lots of posts about oil and wonder if there are any tribologist's on the forum that could put some science behind some of the opinions expressed?

I personally have the following questions:-

1, The original viscosity of the oil specified for a twin cam engine reflected the accuracy of the machining at the time, with modern machining would a newly rebuilt engine benefit from a different grade oil? I notice Rohan specified a 10/50 oil?

2, (one for the engineers) Are modern bearing shells manufactured more accurately these days or is the quality still 1960's standard? I am assuming a more accurate bearing shell/machining could support a thinner grade oil.

3, Twin Cam engines are designed for 20/50 viscosity oil, in lab conditions will there be no difference in flow etc. between a synthetic and non-synthetic oil.

4, From doing some brief reading a fully synthetic oil is able to maintain it's viscosity over a wider temperature range, having lived in Chicago for 18 months I can see the benefit of an oil that stays in specification at the extremes. Is my assumption correct and would a synthetic oil be much more beneficial in certain climates compared to an average UK summer.

I am sure other people have many more questions and can express them better than me but oil, for me, is a very complex subject and something I would like to be a bit better informed on.

[rgh0]

I use Penrite running oil but as stated any cheap conventional oil will do. A yes you need to specific running in procedure to load up the piston rings to bed them in rapidly so you dont glaze the bores


A few comments below on the other questions

I have read lots of posts about oil and wonder if there are any tribologist's on the forum that could put some science behind some of the opinions expressed?

I personally have the following questions:-

1, The original viscosity of the oil specified for a twin cam engine reflected the accuracy of the machining at the time, with modern machining would a newly rebuilt engine benefit from a different grade oil? I notice Rohan specified a 10/50 oil?

RH - The top quality synthetics usually now come as a 10W/50 as the synthetic base oils used give it better low temperature performance enabling a 10W rating. Modern oils and modern machining tolerances allow lower numerical oil grades in modern cars such as 40 or 30 or 20 or even less. Twin cams are typically rebuilt to their original clearances specs and thus you need to stick to a 50 rating oil

2, (one for the engineers) Are modern bearing shells manufactured more accurately these days or is the quality still 1960's standard? I am assuming a more accurate bearing shell/machining could support a thinner grade oil.

RH - bearing shell variation is the least of the issues in achieving the correct bearing clearances. The bore on the caps and the amount of crush when the shell is compressed is much more significant

3, Twin Cam engines are designed for 20/50 viscosity oil, in lab conditions will there be no difference in flow etc. between a synthetic and non-synthetic oil.

RH -The is no difference in oil flow at the specified temperatures of the testing outside of that they may be more variale with synthetics generally being better

4, From doing some brief reading a fully synthetic oil is able to maintain it's viscosity over a wider temperature range, having lived in Chicago for 18 months I can see the benefit of an oil that stays in specification at the extremes. Is my assumption correct and would a synthetic oil be much more beneficial in certain climates compared to an average UK summer.

RH - Yes full synthetics maintain their viscosity of a wider temperature range. This appears as a low W low temperature rating and easier starting when cold and less loss of oil pressure when hot and idling

I am sure other people have many more questions and can express them better than me but oil, for me, is a very complex subject and something I would like to be a bit better informed on.

cheers
Rohan

[2cams70]

If you have an engine failure 99% of the time it won’t be due to the brand of engine oil and the type (within reason). It will be something to do with the assembly, the machining or the quality of reproduction parts. It really is not worth overthinking things and safest bet is something that has a viscosity like the originally specified oil (20w/50) or the oil manufacturers recommendation. A running in oil may offer some benefit due to it having a higher level of EP additives to protect things like camshafts during bed in if they are new or you have new/refaced tappets and no friction modifiers to inhibit bed in of piston rings but again if you have problems it’s root cause is 99% likely to be something else and not the oil.

Personally speaking “cheap oil” could mean anything. At least running in oil should you choose to use it is more of a known specification.