Oil - 10/60

[greenamex2]

Has anybody out there used either Millers Oil CFS 10/60 or the new Shell Ultra Racing 10/60?

The grades seem to suggest a major contribution to my high temperature oil pressure reduction 'problem' due to the overly large clearances required for 9500RPM, but not adding too much drag when trying to start the thing or risking blowing the oil seals when the engine is cold (sorry about all the oil I dropped this year, now solved that one with an oil pump seal retainer, thanks PACE).

I am currently using Royal Purple Racing 41 (basically a 10/40) which is an excellent oil and the engine hasn't blown up yet but, as always, I am seeking improvements.

And yes, I know that reducing oil temperature would be better but there is a limit to what you can do with a wet sump 9500RPM 218BHP 1600cc engine, and I have pretty much done it all.

[Tim Falce]

I assume it is a semi or fully synthetic oil you are using. We have tried quite a few different oils and ended up using Valvoline 20/50 Racing which seems to give a good compromise on hot oil pressure and cooling. This is on a 1600 Lotus twinc, a 4.2 Jaguar and a 1600 Ford CVH. The Jaguar used to have virtually no oil pressure at the end of a race with semi synthetics but now has a reasonably good 20-30psi on tick-over after a race with the Valvoline.

[Al Weyman]

I agree and use a common (read cheap) 20/50. I was using Unipart Green after a reco from a top Rover racer who was having typical Rover V8 oil pressure problems and will have tried them all trust me, but it may no longer be available but that was just a cheap(ish) 20/50. This is for Chevy engines.

I am of the opinion correct or not, that a lot of these modern and very expensive synthetics are really designed to extend the service intervals on road cars and give a slight better performance at cooler tempratures, but do they really have a place in a race car engine that does what, 3 or 4 hundred miles (or a lot less!) before a change.

[graham bahr]

for years i used duckhams Q 20/50 in my race car, thats quite cheap, and still had oil pressure at the end of the race, it wasn't even a very high spec oil, well it was once, but things have moved on, but ia race car will run quite happily on a low spec oil as long as you dont try to do 10,000 miles on it which none of us will.

using Q i did 5 seasons racing without needing a crank grind, i did run a big end eventually, but i'd say that was my fault, time pressures ment i did thre and a half seasons without a bearing change, interestingly all the rest of the bearings in the engine were in perfect condition.

[StephenRae]

Synthetic oil still seems to work at very very high temperatures and must suit modern close tolerance engines but I find 20/50 gives more consistant oil pressure on my FF1600.

[Al Weyman]

Yes I am not talking turbos as i have always steered well clear, that may be a different kettle of fish altogether.

[Chris Griffin]

We use Millers Sport 20/50 in the SD1. Its a semi synth. I would be happy to continue using it. Oil pressures are fine when hot. I have used all sorts in the past particularly Valvoline Racing 20/50 in the Dolomite. I found it hard to find a local retailer that stocks Valvoline any more though.

[Al Weyman]

Yes I believe Gerry has gone over to that now that the Unipart green has been discontinued.

[graham bahr]

Originally Posted by Al Weyman

Yes I am not talking turbos as i have always steered well clear, that may be a different kettle of fish altogether.

neither was i, i was referring to whem my engine was naturally aspirated and reved to 8,200.

i do now use a thin synthetic oil inconjuction with some changes to the oilways and bearing clearances, but that was only for the sake of the turbo

[Tim Falce]

Originally Posted by Chris Griffin

We use Millers Sport 20/50 in the SD1. Its a semi synth. I would be happy to continue using it. Oil pressures are fine when hot. I have used all sorts in the past particularly Valvoline Racing 20/50 in the Dolomite. I found it hard to find a local retailer that stocks Valvoline any more though.

I am able to get Valvoline 20/50 with no problem, I just phone ecktic up and he has some ready for me to collect.

[Al Weyman]

Watford Motor accessories an American parts stockist sell Valvoline and another racers favourite, Kendal.

[Chris Y]

Mint cake?

[dtype38]

Mint cake certainly has high calorific value, but if you use too much of it you tend get a bit of bottom end trouble.

I tried Castrol RS 10/60 in my Jag and not only was it very expensive, it didn't seem to do anything for my fully "race hot" oil pressure. I swapped to Valvoline "Racing" 20/50 and it was much better. Why? because I'd forgot that my engine was designed in the days when the oil did a significant part of the cooling of the engine. As far as I know, modern engines rely almost totally on the water system to extract heat from the head and block. Modern synthetics may be great for tolerating high temperatures, but, from what I understand, they have (relatively) low coefficients of heat capacity and heat transfer. That means if you use modern synthetic oil it doesn't matter how big an oil cooler you have, it won't help you much in keeping the engine cool.

[graham bahr]

generally the main problem using modern thin oils in old design engines centres around bearing clearances, which are generally bigger in old engines, and therefore need a thicker oil to ensure a decent quanity of it actually reaches the big ends rather than all leaking out from the mains

[graham bahr]

i dont know why but theretically a modern 10/60 should be thicker when hot than a 20/50 but in practise isn't,

maybe because the oil is tested at a higher temp than it normally runs at in an engine?

[zefarelly]

I use 20/50 either millers or 76 as they bring it to meets, doing hour long races, revving to 75000-8000 and in temps ambient up to 35 degrees (Dijon in June) I've never had any problems, for the sake of £20 I change the oil and filter after each meeting. its a lot cheaper than £5k plus on a new engine !

[greenamex2]

Thanks for the input so far. I think I'll give the Millers a try.

Out of interest, an oil manufacturers web site (admittedly American) reckoned that you SHOULDN'T change a race cars oil filter too often.

The argument they put forward was that an oil filters filtering capability gets better the more clogged it gets, and is at it's most efficient (filtering wise) just before it clogs up completely.

Not sure what effect that would have on pressure though. Presumably the oil pump has to work harder which puts more heat into the oil making it thinner and then dropping the pressure.

[carsreunited]

Penrite 20/60 for me.

[Al Weyman]

They (the Americans) also seem to advocate the use of a dismantable aircraft screen filter before the filter proper, the idea is to monitor if anything is falling apart by inspecting for particles in the screen filter, I have one with the drysump system I bought from the USA on eBay.

[graham bahr]

Originally Posted by Denis Bassom

Out of interest, an oil manufacturers web site (admittedly American) reckoned that you SHOULDN'T change a race cars oil filter too often.

i tend to change the oil every couple of meetings and the filter a couple of times a year.

[Al Weyman]

Why do you feel you need to change so frequently Graham?

[grelley]

One of the things that destroys oil is contamination from the combustion process such as acid,water and fuel contamination diluting the oil. In a competirion car providing that the mixture strength is correct, the engine will run hot enough to burn these contaminants off, and/or prevent them from forming in the oil. Providing there is no mechanical debris in the engine then I think oil changes can be at least for a season and change the filter at the same time. A gauze filter in the line is good insurance and can be checked after each meeting, as well as a removable magnet in the sump which can be cleaned and inspected, to trap metallic particles which can then be analysed.
I have run approx 650 race ks on oil and filter (Castrol RS) with no problems. A subsequent engine o/haul due to another problem revealed no undue wear.
It is more important to have a constant supply to the bearings etc.

[COLIN STUBBS]

we have a local small oil manufacturer here in lincoln who produces a 20/50 grade race oil. its really good stuff and cheap. qualube special f race oil. witham lubricants. we struggled like hell with op on essex v6s before finding out about temperature v pressure etc.

[zefarelly]

the old oil filter trick sounds like a load of balcocks to me, surely if you want to trap more debris you've either got the wrong filter medium, or you've starved the engine of oil and bits are falling apart ? a filter will be at its best when its new. I did my apprentiship working for a pneumatic conveying and Industrial vaccum cleaning company so I think I talk sense on that one, any filter will do 2 things, restrict flow and stop certain size particles passing through. I suppose you could argue you'd be better off with a cyclonic pass and a magnetic trap somewhere in line, but its all getting a bit silly really when I've got a Ford Cortina and a filters £3 from Halfords !!!

[greenamex2]

Colin, unfortunately 20/50 is going to be a bit thick for my engine on those cold wet Snetterton days. It's a pig to start on a 10/40 as it is!

Zefarelly, multiple filters did seem as bit excessive to me. My (numerous) experience of race car engine blow up is the time between the problem starting and the engine blowing up is usually either seconds or really obvious (smoke etc).

By 'best/most efficient' the Americans seem to be ignoring the effect on pressure, presumably their big inefficient V8's have got so much spare horsepower they can afford to lose a bit more through the oil pumps.

Which reminds me, I must find a bigger oil filter for my engine.