Assuming that the oil quantity in each of the quart containers is accurate, the result of adding exactly 5 quarts of oil, plus a filter, was that the oil level on the dipstick was short of the MAX marking by close to a 1/4". Knowing that the amount of oil added was correct, I remarked the dipstick to reflect the correct minimum and maximum levels. Regardless, the level was between the MIN/MAX marking, so much ado over nothing.
Hey Jerry !
The actual Oil Quantity / Level needed is a bit of a juggling act in these power units.
Looking at the engine, we need enough to charge and lubricate the engine Lube system + a sensible reserve + enough for cooling and as hot oil comes down out of the engine while running, give it enough time to dissipate some heat before being sent around again. Actual Power Outputs used obviously come in to play here and this can be where Oil Coolers can be useful, but all too often, they are fitted inappropriately, with higher power engines, driven using low and moderate power outputs.
The other part of the equation is the gearbox, here we also have heat to dissipate, but no forced Lube system, so we want the level to be about half or just under that, way up the geartrain. Once again, cooling comes in to play here too and having a level that's too high, will not only sap power, but also drive up the Oil Temps in a big way. Less is better.
On balance for just about any street driven Mini, I would suggest rather being too concerned with quantity, I'd suggest aiming for a level around 1/2" below the centre line of the geartrain when charged, but cold and not running.
While not the topic of this discussion, I'll just mention here the dilemma 'we' (as Mini and Moke owners) face in regards to Oil Grade and it's not as 'bad' as we may think.
Ideally for ambient temps in the 0 to 350C / 32 to 950F mark, considering the engine in isolation, a grade of 10W40 is quite adequate, going to a heavier grade only heats the engine more and degrades the oil quicker.
And here's where it might be surprising. Our geartrain was directly derived from the Austin A30 / A35 and flowed on to bigger / heavier vehicles, including the Morris Minor, including the Van and Pick-up versions. The recommended grade of Oil for these gearbox is also 10W40, not a 'normal' heavy traditional gearbox grade of 70 or 90 weight.
When we come to the differential in these RWD cars, from which the Mini one shares just about all parts with, an 80 - 90 weight is recommended. When I look at how the Diff Pins and Sun Gears wear in our Mini Gearboxes, it's clear to me that they are not an ideal design, while they are intended to be a splash / dip fed unit in how they are lubricated, they really need a pressure feed or even just squrters would help. I believe the shape of the Diff Centre and in particular, the small, poorly shaped windows in them causes the oil to centrifuge out of them, causing them to run largely dry. When I look at the Diff Pins, they appear to me to have worn from lack of any oil So, while I've knocked lighter grade oils, a heavier weight would likely be worse.
I'll finish by saying that I've been running with a local Oil (available in the UK), Penrite HPR30 which is actually a 20W60. I do feel it's too heavy, but I use it because it's additives and detergents are better than anything else I've ever used, I have found it takes around 200 - 300 km of continuous running to get it up to temperature, I can feel it, it runs quieter, and there is a notable difference in power as well as reduced fuel consumption. If this company made a similar oil in a 10W40 (or even a 10W50), I'd swap to that in a heartbeat.
