I'm guilty of driving with one hand on the gearknob if i'm honest, pretty good with everything else.

When I was reading I missed the "gear" bit and I thought - a brave confession!

So 1st , 2nd and mabie 3rd is all good?

If you redlining in 3rd you are already at 3 digits

The cooling the turbo thing is ridiculous. Most cars, and our CR engined diesels now keep the oil pump going after you turn off the engine, for the precise reason of supplying fresh oil to a hot turbo.

How do they do this then? The oil pump is mechanically driven off of the crankshaft; when the crankshaft stops so does the oil pump.

That said, oil feed designs to turbochargers do include a siphoning effect, so that there is a small trickle of oil pulled through the turbo bearing after shut-down to help mitigate the heat sink effect that can oxidise the oil. The other points above are valid though - unless you have shut down from a full-power uphill slog, the turbo will be relatively cool anyway. Worse case that most people might encounter is a motorway service station, where you might be suddenly stopping from 70+ leptons, perhaps fully-loaded.

Umm, no!!

Modern, multigrade oil - cold oil is thin, hot oil is thick, so for example 5W-30 is at SAE5 viscosity at 0c and SAE30 at 100c.

JerryT has already addressed this but to agree with and expand upon his answer, there are not many liquids that can repeatable, reliably and reversibly thicken when heated. The two numbers used in the SAE viscosity classification are taken from different scales, tested in different ways. The "xW" (or 'winter') number tells you the relative viscosity when cold and is a measure of the flow and pumpability of the oil at a cold temperature. The temperature that the "cold cranking simulator" (CCS) test is carried out at is (x-35)°C, so for a 5W-xx it is -30°C, a 0W-xx is -35°C and so on. As well as a cold cranking test, there is also a low temperature pumpability test, which is carried out at (x-40)°C. The number itself (0, 5, 10) is arbitrary and tells you only whether one oil is thicker or thinner than another at a given temperature, but tells you nothing of the actual viscosity result (unless you are familiar with the SAE J-300 specification).

The second number tells you about the viscosity at 100°C, which is a reasonable average bulk oil temperature for an engine at operating temperature. There is also a HTHS (high temperature, high shear) test at 150°C which represents the ability of the oil to form an oil film under high shear environments, such as in a crankshaft bearing. Once again, the number (20, 30, 40 etc) is arbitrary and relative only, it does not tell you what the viscosity actually is. JerryT got close on the viscosity limits for SAE 30, being 9.3-12.5 cSt (mm²/s).

Oh, and while I'm on the subject, another common misconception is that gear oils are really thick, much thicker than engine oil - after all, look at the numbers: 75W-90, 80W-140 etc. Perhaps you should know that gear oils are tested according to SAE J306, which uses different methods, temperatures and results. In fact, a xxW-80 oil has a viscosity of 7.0-11.0 cSt at 100°C, so is thinner than many engine oils.

TL;DR - all oils get thinner when heated up. Multigrades just don't thin as much as monogrades.

Treat your car like you would your mistress.

Lock it away and only get in it at the weekends?

^^

I am not putting a bonnet on my car!