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Shell W80 and W100 oil temperature range - surprising! (15W50 seems pointless)

here

I don’t think many people realise the “100” oil is not supposed to be used below +16C.

If one takes this table literally, straight oils are not very usable in the UK, where the temperature could vary over a much bigger range during the same day.

Administrator
Shoreham EGKA, United Kingdom

I think most people know that, but it’s obviously not that the oil doesn’t “work” at 14 degrees. As always, shades of grey.

I use W80 all year ’round, even in high summer. That said, one rarely ever flies at above 21 deg C for a long time. I would not use W100 all year ’round in central Europe.

Mainz (EDFZ), Germany

Most people might know that (actually I am pretty sure most people don’t) but that isn’t the point, which is that

  • the temp ranges are only for starting the engine, and
  • the average private GA plane can easily go from say September through to following April, between services, and
  • almost nobody changes their oil between services, for the purpose of getting a different starting temp range

one rarely ever flies at above 21 deg C

Once in flight, the ambient is irrelevant, because the oil warms up to its regulator-controlled temperature. This is (degF) from a 1hr flight

Administrator
Shoreham EGKA, United Kingdom

There is a surprisingly narrow overlap in the OAT ranges of different grades!

ESKC (Uppsala/Sundbro), Sweden

Yes, but again, shades of grey. Also, you could always use a mix of 80 and 100 and get 90.

Peter, you are of course correct on the start-up being mentioned as the basis for that table.
In that case, my rationale is that cold start-ups are more critical than warm start-ups in terms of engine wear, so if in doubt, it is probably better to use slightly lower viscosity oil.

Last Edited by boscomantico at 17 Jan 09:36
Mainz (EDFZ), Germany

I’m with Bosco on this one. In northern Europe (W)80 should cover you pretty much year round, and you could always mix some (W)100 in during summer.

AeroShell is not the only oil availalble. It has been well documented that there are alternatives perhaps more applicable. Ed Kollin makes makes a very good point that it’s not wear that kills our GA engines, it is mostly corrosion causing damage leading up to a tear down of the engine.

Last Edited by complex-pilot at 17 Jan 10:32

If one takes this table literally, straight oils are not very usable in the UK, where the temperature could vary over a much bigger range during the same day.

Although I don’t disagree on this based on temperature range a large proportion of aircraft fly say 50 hours a year. I wonder if the reduction in internal corrosion outweighs the benefits of the few starts it will do outside the 80 weight oils temperature range.

The current outfit I work at the Cessna’s get Total 80 and the T67 aeroshell 15-50 at service and they both get topped up with 80 in the summer and 100 in the winter. The later probably for historic reasons as much as anything else.

both get topped up with 80 in the summer and 100 in the winter

Interesting…

Mainz (EDFZ), Germany

During operation, the oil temperature is constant anyway, due to the thermostat bypass on the oil cooler.

Administrator
Shoreham EGKA, United Kingdom
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