I'd be interested to know what owners of high performance A-series engined road Minis recommend as to what engine oil to use.
I've just had a 1380 road engine built which I'm still running in.
I don't really know what oil to use:- Which brand? Which viscosity? Synthetic, semi synthetic, or mineral based? Oil change interval on hi-perf road engine?
The A-series being a non-modern design and also given that the oil also has to take care of the gearbox makes it hard to know exactly what to use.
I'm guessing that a fully synthetic like Mobil-1 might be too thin for the A-series and gearbox?
You are correct that something like the normal Mobil-1 is too thin for the A-series. There are however heavier synthetics that are useful. The main advantage of the synthetic in a Mini is that it can lower the running temperature from 10 to 20 degrees. Given how little coolant there is in an A-series this can be very helpful on hot-running engines.
Synthetic in the gearbox is something that there has been a lot of debate about. While I know half-a-dozen people running synthetic with no problems there is a case or two where gearboxes have failed using synthetics. My recollection is that they failed very shortly after the switch. Since most gearboxes in the last 30 years have used engine oil or automatic transmission fluid as a lubricant it is hard for me to imagine that the lubrication properties of synthetic were to blame. It is possible that the very thin grades of synthetic could cause problems in a Mini gearbox but it's hard to say. Personally, if I had a hot running engine and the cooling system was in top shape I wouldn't hesitate to go to a 40 or 50 wt. synthetic.
With mineral oil and in the right circumstance with synthetic I would change every 3000 miles. I have read higher change milages but given how cheap non-synthetics are I would go with 3000 especially with a
1380. In the U.S. Valvoline Racing was my top choice since it had a large amount of zinc in the additive package. This should help with the gearbox and diff. I have no evidence that it actually helps but it couldn't hurt. I think the formulation has changed in the last year or so but I can't find the documentation on this.
It is critical on an A-series to use a good oil filter. The Volvo
140/240 4 cylinder filter made by Mann is excellent. Another is the Wix 51342 it is well made and has a larger capacity.
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