I’m unable to reply to you for some reason on my s-v6 track car thread for some reason.
I am doing track days at Bedford and donington in February and March.
I currently have Millers CFS 5w40 NT+ engine oil, but it’s abit pricey to be swapping out after a track day.
Would you recommend any other oil to use for the days and should I replace engine oil after the track day?
I’ve found this other Millers engine for motorsport if you think it’s suitable?
I'm sorry for not replying earlier, but only just saw your post yesterday and things still a bit hectic.
But to be honest, it was also; in part, to think of a response. These engines are very expensive to maintain and just physically doing some work on them is not cheap.
The work I am undertaking on my Brera engine and, once it replaces my 159's the work I will be doing to that, is a real labour of love. And it needs to be, as pockets need to be a lot deeper if mistakes are made.
Advice on type of oil? I love what you are doing with your car and if mine takes much longer to get back, my license will have been revoked and the only place I will be able to drive it will be on a a track.
I cannot in all conscience and will not on principle give advice on what people should do with their cars. Any mistakes must be their own, which means you need to do a lot of digging for information - there is a lot to be had, as I have found.
For instance, I had in my last post concluded I would fit a scraper plate to try and disrupt windage and in particular recover the spent spray jet oil faster and return it to the sump. But speaking with my engine builder, his advice was not to. He showed me the sump from one vehicle which had cracks in the baffle/windage plate due to vibration. He also showed me a scraper plate which was fixed by the sump/block bolts. It too had suffered fatigue and was showing signs of cracking.
My engine failed, not for lack of oil, but most likely because of the delay in the oil being recirculated to the sump. Essentially, the engine capacity is too small and the oil gets no settling time to allow entrained air to precipitate out. It is not for nothing, manufacturers chose oils with good anti - foaming characteristics.
Windage will drag combustion by - products; air, hydrocarbons and moisture as well as burnt oil, spent lubricating oil and spray jet oil, into suspension and unless the returning oil is allowed time in the sump for all this entrained air and moisture to precipitate out, it is simply taken up by the oil pump and compressed into the oil and returned to the galleries/oil-ways.
All the articles I have read state, whilst these components remain "Dissolved in the Oil", it is less problematic. But restrictions in galleries cause any dissolved components to precipitate out into entrainment. This happen on the inner radii/edge of any restriction, but successive restrictions are very difficult to analyze, other than to say, there is a very rapid change of dissolved components into entrained components.
The net effect being, the "Hydraulic Nature" of lubricating oil is lost and it becomes compress - able. The oil becomes spongy and exerts less pressure on essential components such as tensioners. (Problem Number One).
However, with dissolved components, reversing to entrained air/moisture, one gets two problems for the price of one.
The first, I have given above. The second is:- the further away from the oil pump, the greater the pressure drop. Also the oil has been exposed to a greater temperature gradients - vis a vis it is hotter. The pressure drop itself will cause the bubbles to expand and the increased temperature causes a reduction in viscosity, so the bubbles can precipitate out faster.
This is why my engine suffered damage to number four and five - five failing, big end bearings. Why four and five, when number six is furthest away? because the oil feed to number one and number six journals are not Siamese twins.
Meaning, number One Main bearing and number Four Main Bearing, supply only Number One Cylinder Big End Bearing and Number Six Cylinder Big End Bearing, respectively.
Big Ends Two and Three share oil from Main Bearing Number Two. And Big Ends Four and Five share oil from Main Bearing Number Three.
Accordingly, the physics state; "the expanding bubbles, due to reducing pressure and increasing temperature can withstand high sheer pressures, to the extent that they can prevent oil from flowing." Effectively running bearings dry!
It has been suggested to me, a second function of the spray jets is to help remove entrained air/moisture, but whilst entirely plausible, I think the distances are too short to be that effective. Of course, they may more effectively, if the degree of entrained Air/Moisture is low. (Problem number Two).
One cannot prevent Combustion by - products, air and moisture from being absorbed into oil. But there are ways to reduce it and it's effects.
Likewise, one cannot prevent absorbed products from precipitating out into entrainment - bubbles in the oil. But one can reduce it.
The simplest way of minimizing the problem is:-
1) Change oil on a very low mileage basis.
2) Eliminating restrictions, mitigates Problems One and Two.
3) Increase the capacity of the oil in the engine so it has a longer rest time before it is
4) Avoid prolonged high revolutions in low gears; where blow - by is greatest, as is the vortex created by the rotating crankshaft and journals, whereby these products can be more quickly absorbed by the oil and foaming becomes a major issue.
With this engine and it's low capacity of oil, delayed returning oil, can result in this foam being drawn up by the oil pump and compressed into the oil - ways, because the sump level has dropped - at 7,000 rpm the pump can empty the sump twice as fast as at 3,500 rpm, the level having dropped and foam (aerated oil) pulled into the pump.
I write these paragraphs, not just as a reply to you, but also for my own benefit. I cannot advise you on what oil to use other than to stick with that recommended. Thinking off the top of my head, no racing team would re - use oil and given their engines are re - built on a regular basis, top grade oil is most beneficial in this instance.
The fact is, your engine is not new and will already have suffered wear. So a top grade oil, which is very effective with tight bearings, may less effective with an engine with bearings less so.
Understanding the problems better; new oil, is always going to be better than old oil, even if it is the highest spec. Avoiding entrained air is key and old oil may have had time to rest and disperse air, but there is still the issue of by - products, trapped in the oil, such that it's effectiveness as both a lubricant and a hydraulic medium is reduced.
My choice, and this is not a recommendation, I will use what Alfa recommend. Even though my rebuilt engine is effectively new and bearings are "Tight". But on the track, I would spend some time between runs to allow my engine to recover, recheck the oil, then steadily drive home. AND IMMEDIATELY DO AND OIL AND FILTER CHANGE.
Good luck with your car.