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Is there any point in multigrade oil IF the engine starts ok?

Cold starting

It seems, reading various stuff, that W80/W100 + Camguard is every bit as good as 15W50 (Aeroshell). There seems no evidence that one type of oil makes an engine last longer than any other. Camguard itself provably substantially reduces the wear rate of the soft metals (other threads on this) but I am not aware of any evidence that it makes a difference between an engine reaching TBO or not.

However, 15W50 is thought to be necessary for cold starting e.g. at 0C temperature. Is that actually true? Has anyone tried it?

There cannot be a reason for multigrade oil in flight because a typical Lyco/etc engine has a temperature controlled bypass valve for the oil cooler.

Shoreham EGKA, United Kingdom

Peter wrote:

However, 15W50 is thought to be necessary for cold starting e.g. at 0C temperature. Is that actually true? Has anyone tried it?

In theory, light oil are good for cold start and cold runs while tick oils are better for high temperature/mechanical loads where light oils may fail

But the two types should still have the same viscosity/lubrication profile under different thermal/mechanical loads, if that is the case they should have the same chances to get you TBO depending on how you fly each of them?

If you want to reach TBO at 99% power and max CHTs get a heavy oil while if you want if you want to reach TBO at 55% power and min CHTs get a lighter oil? This my pure guess, I go with 15W50 at 65% power

Last Edited by Ibra at 17 Oct 21:53
ESSEX, United Kingdom

Why not Philips 20W50 ?

It’s not really available. Past posters went to a lot of hassle to get it, and AFAICT the case for it is unproven.

The UK gets temps down to 0C and sometimes below (though almost nobody flies when it is that cold) and up to say +30C, yet most people manage fine with W80/W100 which is the most widely stocked oil here.

So I wonder what is the lowest temperature with which W80 will work. Presumably it depends on the starter motor. The stock Lyco starter turns the engine very slowly, but it also draws comparatively little current. The high speed starters spin it much faster but draw extra current – there should be no free lunch at all.

Shoreham EGKA, United Kingdom

Cold starting seems to be an issue with continental starters, my contention is it is cold non-starting that is the issue as the starter turns the engine that is reluctant to start due to environmental issues , a mediocre battery and ( in some cases ) poor pilot technique.

So this being the case the oil is only a small factor in the non-starting equation that is overloading the starter.

My solution to the problem of non-starting ( on my Lycomings) was to fit Slick Start units to all the aircraft, as these aircraft operated on a flying club pilot technique is a major factor in overloading starter systems. The Slick Start ensures that as long as there is some fuel available the engine will start. I am sure that the Slick-start units have more than covered the cost of fitting them in saved batteries and starter motors.

I know this has moved away from the subject of oil but IMO oil type is not a major factor in Continental starter failures.

I am still looking for the W80 cold starting data point

And hopefully it won’t be this solution

Shoreham EGKA, United Kingdom

not so difficult:
AeroShell Oil W80 for cold climate regions (-17 – 21°C)
AeroShell Oil W100 for temperate regions (15 – 30°C)
AeroShell Oil W120 for warmer climates (above 26°C)

Thank you. In minus 17C the average male pilot will have more pressing problems, apart from starting the engine so W80 sounds fine.

Shoreham EGKA, United Kingdom

Around here, we call W80 “Winteröl” and W100 “Sommeröl”.

I use W80 only. No 15W50 since I don’t like it at all, at least for Continentals….
And no switching between W80/W100 either, since I can’t be bothered organizing oil changes exactly in autumn and spring.

That said, I am generally more worried about cold starting protection than about issues in very warm temperatures.
Also, I tend to not fly in the south of Europe etc. in high summer and why I do, I am usually done before 11 am….

Mainz (EDFZ), Germany

Regardless I think I would like to switch to a multi-grade for winter ops in the UK.

Total do AERO DM 15W50 which I hear is exactly the same as AeroShell W 15W-50. Which is a semi synthetic and I hear lots of stories saying this isn’t an idea oil for aircraft run on Avgas

Total also sell TOTAL AERO DM 20W60 which I have also heard is in fact Phillips XC 20W50. Does anyone know if this is the case or have any experience in using this oil? And is it semi synthetic or purely a mineral based oil?

Phillips 66 X/C 20W50 which I think would be ideal is just not easily obtainable in the the UK and where it is available the price is a bit silly.

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