K Series Oil Grades

[Andrew Willcox]

Hi,

Looking to complete my first oil change in ex race 1.6 K Series, wet sump with Apollo tank.  Foam and filters ready, just need to sort the oil.

Trying to understand the trade between 10W40 and 5W50.  Sounds like 5W50 is recommended for extended track us but what are the downsides in “normal” everyday use?

I intend to use the car for track days / sprints next year, not sure if that justifies the motorsport oil.

Thoughts and Advise

[Jonathan Kay]

1. There's a vast amount on this in the archives and IMHO it doesn't answer your question conclusively.
2. Anything recommended in Caterham's Assembly Guide or Handbook will be fine
3. ​I use Comma 5W-50 for road use and trackdays as it's what Caterham recommend for track driving which is probably the most wearing on the engine.

Have you made your decision on the Great Foam Question?

Looking to complete my first oil change...

Alcester Racing 7's notes.

Jonathan

[Andrew Willcox]

Thanks Jonathan,

I see both grades recommended in various places.  Also sensitive to rattley tappers when cold and I’d don’t know whether 5W50 exacerbates this problem... hence trying to get to some of the theory behind the grades.

Regarding Foam, I hadn’t picked up on this debate. Assume replacement at every opportunity is food practice.

[Jonathan Kay]

... hence trying to get to some of the theory behind the grades.

Ah... that is answerable. It's whether it matters in practice that's the difficult bit! :-)

Regarding Foam, I hadn’t picked up on this debate. Assume replacement at every opportunity is food practice.

Some do that, some inspect and decide, some remove and fit a modified gasket... engines have been lost over this.

Jonathan

[TomB]

I generally use 5w-40 fully synthetic on my 1.8 K series, often Halfords made by Comma.

[Wrightpayne]

Ditto what Tom said - 5w40 halfords fully synth.

Ian

[Jonathan Kay]

Please could people say why they made their choice. Especially as I don't think that there's much evidence that can be brought to bear on the decision.

Thanks

Jonathan

[TomB]

For me and my K series Supersport....

Fully synth = Best quality.

Grade = as recommended consistently for general use. 5w-50 appears more suitable for track. 

Type = Halfords, made by Comma, for cost, regular deals and accessibility. Comma was recommended by CC for several years during the 'Age of the K'.

My view has generally been that the frequency of change is as important as the type of oil - so for me changing on every couple of thousand partly negates the use of filling with the highest spec oil possible.  At the end of the day, mine is more or less a mass produced K series used as a road car with an occasional track day. It doesn't need the highest spec of oil that you might use on a very specialist race engine that lives at the top of its RPM. 

All IMO of course, and Im sure someone will be along with a contrary view!

[Paul Mason]

I have bought some Comma Motorsport 5w 50 which is what I was told was in the car and right for the car (Pace dry sump). No additional insight that that from me I’m afraid.

What I would say is does indeed sound like the tappets rattle while they fill up on a cold start on a cold day. I start and leave to tickover for a while anyways and the noise goes after 30 - 60 seconds (depending on how cold it is it would seem).

Please note, the above statement is an observation from me putting my lug against the Cam cover and the noise seems to be top end and quietens down so guessing tappets)

Oil pressure 60psi immediately on start up, will increase to c. 80 under load (c.4k rpm) and once oil fully warmed (60-80 degrees though small scale and poor eyes make that difficult to be more exact) seems to settle at 35psi pressure

Not sure I’ve added any value?

[Andrew Willcox]

Thanks for the inputs...

Checking the Owners Handbook it actually recommends 0W-40 (not 10W-40) road or 5W-50 track.

0W-40 only seems to be available in premium brands that I'm not going to pay for - and I'm sure a slightly worn engine would benefit from a slightly thicker oil!

So it looks like it's a choice between Comma 5W-40 and Comma Motorsport 5W-50.

Looking at the Comma spec sheets for the oils, there is quite a difference in the viscosity @ 40oC (5W40 @ 80cSt vs 5W50 @ 103cSt) so... in the interest of improving flow at normal temperatures (tappet lubrication) I think I'll follow Tom and Ians advise and go for the 5W-40 over the winter months.  Will keep and eye on oil pressure next year as the weather warms up.

Andrew

[Wrightpayne]

For me the reasons are 1) Price - 5/40 generally on offer more often and needed 7ish litres when I had the Apollo 2) no noticeable difference in oil pressure readings on either road or track and 3) relatively low mileage p.a. between oil changes.

Ian

[Paul Mason]

I know it wasn’t the purpose of the original post so apologies Andrew, but am understanding thus far that a 5w40 is slightly thicker than a 5w50 and does that mean the tappets will fill a little quicker?

Also, what is the desired oil pressure range when warm on tickover, moderate and heavy loads?

For reference, 1.8k, VHPD head, piper 1144 (I think) cam and springs, dry sump

[Toby S]

1993 1400 k supersport - wet sump

Grade used:- 5/50 used as that's what the handbook stated back in 1993 - didn't state to use different between road or track use - I'm not an engineer hence can't see a reason to change

Make:- Comma - best value especially on internet deals - last bought 15 litres (3 cans) for around £60 a year or so ago when it was on offer - can't remember where - seems fine and also my 1400 engine has a tendency to burn a bit (I'd guess possibly worn valve stems, but given other than burning a bit of oil it runs and revs like stink so I'm not that bothered) 

Oil changes - Once a year circa every 4,000 miles, although mine is all road use

Foam or no foam - I go for foam (again I'm not an engineer and assume engine designers knew what they were doing) - meant to reduce oil surge - changed mine last year and would plan to change every second oil change - every second year

Oil pressure - 4 Bar (56 PSI) on start up tick over, blipping up to 5 Bar (70PSI) on throttle blips. Once warmed up 1.5 - 2 bar on tickover (20-28 PSi), although increases to 3-4 Bar under load. Drops slightly on hard acceleration and cornering, although much less so when oil levels are at max mark on dipstick - key is to make sure the oil is topped up to the max at all times to ensure oil pressure maintained.

Hope this helps

[Andrew Willcox]

Paul,

5w40 and 5w50 will have the same viscosity at 0oC (hence the same 5W.

As temp increases the 40 will thin more than the 50 hence the lower viscosityat 40oC.

Im trying to be an engineer and working on the assumption that Lowe viscosity will help top end lubrication at “normal” temperatures.

Assuming the higher viscosity of the 50 is only really a benefit at sustained high temp running.

Makes sense to me... but I’m sure there are alternative theories!

Comma oil ordered from Amazon last night @ £25 per 5l

[Jonathan Kay]

Thanks for all the reasons: that makes it much more interesting.

Comma oil ordered from Amazon last night @ £25 per 5l

At some point you have to jump! You'll be fine.

Jonathan

[Paul Mason]

Thanks Andrew......I think I understand