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.

[512BB]

I have written this before. I proved, to myself at least, that using expensive oils, £30 +, is a waste of money.

When I rebuilt a twin cam after 40k miles in my ownership, there was no measurable wear on anything, including the timing chain, and I just put it back together. Crucially, I cannot remember as I write this, if I replaced the bearings I will have to refer back to my notes later.

Anyway, over those 40k miles, I slung anything, oil wise, in it, but always a mineral, branded oil. But the key thing about that is, the oil was always changed after 3k miles. So long as you do that, your engine will stay in fine fettle. Oil, any oil within spec. is the lifeblood of an engine. Keep it clean.

Leslie

[RichardHawkins]

SNG

I am not tribologist, one of my Lotus owning friends is but he never posts, as he does not wish to be involved in a dispute.

Along time (50 years now!) ago I worked for a mining company which operated a fleet of off highway dump trucks. These vehicles created their own little dust cloud as they moved. We could not get the service life that the engine manufacturer expected. Our oil supplier (Shell) installed an oil analysis lab at our mine, which showed oil contamination (usually silica) and recommended changing oil, oil and air filters more frequently. We got the expected service life from the engines. Shell sold more oil, cheap compared to the cost of engines. One of the things that surprised me was someone referring to the air filter as the primary oil filter.

This is just a long winded way of saying oil and engine cleanliness is very important.

Richard Hawkins

[tonyabacus]

Synthetic oils can be very penetrative and will find any small inconsistencies to leak out. By way of illustration we ran some Porsche workshops a number of years ago. A number of customers came to us complaining of leaks and losses, a good number having had their cars serviced by the main dealer network using Mobil ! as promoted at that time by Porsche AG. Whilst this oil seemed to work fine on the newer models from 964, 968,986, it was not so good on the older 911, 356 models. In most cases we convinced the owners to change back to the likes of Castrol or Shell which if not stopped the leaks reduced them considerably.

One of the other replies above alludes to modern materials which does have a part to play, as materials and tolerances have changed over the years meaning that manufacturers have worked with the oil companies to improve the oils as manufacturing techniques have developed.

Our Lotus engines were developed alongside some of these earlier oils which meant they were more suited to the manufacturing materials and techniques of that time. Except for those racing these engines, most of us do not tend to give our engines a hard life and therefore the original 20/50 grade oils are more than adequate. It does of course rely on regular servicing and oil changes and not just leaving them ticking over for long periods where bore wash can contaminate the oil. You may also read from some of our friends in the USA about oil changes every 3000 miles, but bear in mind that they had access to their own oil supplies at very low cost compared with us in the UK, which made changes viable.

As a final point, when we buy a car we never know how it has truly been looked after by previous owners. Storiesn abound regarding engines where the sump has been found to have heavy levels of sludge in the sump when dismantled. Unless you drop the sump you will never know. Looking at the oils market why are there so many different types of oil available, they all perform different tasks. So when you rebuild your engine remember to use a flushing oil which will help remove deposits from the interior walls and components, before replacing the oil and filter. I suggest using it at alternative oil changes or after around 5000 miles (service intervals).

Therefore don't buy the latest oils thinking you will gain some vast improvements, in some cases and my experience it is better to use the type of oils that the manufacturers used unless your engine builder for whatever reason suggests otherwise.
Tony