Engine Oil update

[DavidOliver]

After running-in a rebuilt engine I am looking at deciding which engine oil to use.
I have previously used Castrol Edge synthetic despite the considerably extra cost.
Now looking at Castrol Edge oil products and specifications I cannot see a reference to sinthetic (nor synthetic)
There is a Castrol Supercar product for expensive top level sportscars at a cool 96 Euros per 5 litres.
Plus a reference to a Titanium additive which it claims goes harder at high load and then reduces. It does not say how it does this, if in fact it does anything.
Our engines are relatively medium revs and low pressure at tickover, designed before Synthetic was available (just)
I am considering a reputable make (Repsol) 10/40W which here in Spain is available across the country if I need to top up.

So what now do forum owners recommend?
And can anyone really explain how an oil can be considered viscosity of 10, 20 or 40 across the heat range of our engines.
Some Lotus engine gurus say that modern oils are so complex that simple viscosity conditions are not the most relative.

Dave the cog

[ianhateswork]

Take a look at mannol 10w/60 fully synthetic, i have been using it for a couple of years without issue.
Gives me excellent pressure on tickover when hot.

ian.

[Lotus-e-Clan]

Consider zddp content too. Modern engines with roller cam followers don't need high zddp, and modern engine mods (cats) designed to meet EU emission targets, require low zddp. So today's oil, specifically for moderns, have low zddp.

Our engines (900 series) have flat cam followers which require high zddp due to the extreme pressures between follower and cam lobe. The zddp, at operating temperature, coats the high pressure surface of the follower, If you use modern low zddp oils, no matter the viscosity, you might end up with follower wear like this...


This is one of my Cosworth steel buckets and a billet steel Imp race cam after using oil with a low zddp. It was Gulf triple ester racing oil 10w60. The damage set in fairly quickly. Won't make that mistake again. Valvoline VR1 Racing is a safe bet for high zddp. I now use either 5w/50 fully synthetic VR1 or 20w50 mineral VR1. Both have a high zddp content.

[Roadrunner]

My fully rebuilt and upgraded and bhp elevated engine runs on castrol edge and no issues.

[Pete Boole]

I'm also planning to use VR1 in my supercharged 912 once it's run in.

Pete

[Lotus-e-Clan]

I'm also planning to use VR1 in my supercharged 912 once it's run in.

Pete

For my Clan's engine refresh last year, I used this breaking oil for the first time.

Unsurprisingly, piston ring seal and compressions are better this time compared to the initial build way back in 2006 when I used cheap 20w50 to break it in 🫣
The scary bit is that when this 15w50 Driven breaking oil is hot (80+C), it has the apparent viscosity of something like 0w20! Oil pressures drop significantly on tick over, and on hot oil drain down, the oil runs out like water! I must add that the Clan's large Range Rover Sport heat exchanger is very efficient, and the coolant source is direct from the head outlet, so oil temps rise to 82C within 15 mins of running in the garage where I did the initial start up and cam break-in. Results are worth the brown pants moments though.

[DavidOliver]

Peter K, many thanks for your advice on engine oils.
In particular the reference to ZDDP based oils there is a strong reference to flat cam profiles requiring a zinc content in oil, a possible reason for your Cosworth cam follower suffering.
I have traced a post Re-profiled Cams and the comments made by Tim Engel dated 24 May 2021 and subsequent comments. You also contributed on this post. This confirms that both 107(LC) and 104(HC) cams are flat and therefore should benefit from ZDDP oils.

I was concerned I could not obtain a ZDDP oil in Spain, and have been pleasantly surprised that Amazon will deliver in 2 days a 5 litre Valvoline VR1 at 56€.
At this price I can afford another 5 litres for topping up.

Many thanks again Peter.

Dave the cog.

[Lotus-e-Clan]

Glad to help. The approximate zddp numbers seem to be:

Modern oils for rollers with cats 800 ppm or less zddp.
Racing flat followers 1300 to 1500 ppm zddp.

You can go too high apparently, so adding bottles of zddp additive is not recommended.

Just arrived this morning for the 89SE. The big K&N 3001 filter is non std. I have a remote filter block in the Excel.

[Pete Boole]

I also used to use Joe Gibbs oil in the Chevy V8 - was recommended by loads of guys in the USA - good stuff.

Pete