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My son and I are nearing the end of a total rebuild of a Mk111 Midget. I would like to run the engine on fully synthetic Shell oil but we are unsure wether we should "run-in " the engine first on Mineral oil. PS. Mobil 1 in the USA is only 4.50 dollars a quart. We seem to be paying over the odds here.
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I WOULDN'T USE FULLY SYNTHETIC IN THIS OLD A SERIES ENGINE. YOU WILL PROBABLY GET A LOT OF LEAKS.
HJ
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My experience (Morris Minor) is that old A series engines leak no matter how carefully you screw them together! However, most of them were built when multigrades were a novelty and in 1958 my Minor is recommended to run in the UK on a straight 30 oil. Now, I agree that a multigrade is better, as it gives a lower cold viscosity, so reduces cold start wear. However, even the latest 'light' oils will tend to be a 30 or 40 at operating temperature, so there's no reason why leakage rate should be worse than for the original oil.
Don't forget even an oil with a cold viscosity of 10 is still of higher viscosity when cold than a hot 50. They all thin out - it's just that multi grades don't thin as much as a monograde. A 10/40 is equivalent to a 10 when cold, but equates to a 40 when hot. I know that BL or whoever they were tended to go to 20/50 oils when they were available, and these may reduce leakage a bit, but I wouldn't worry too much. I'm currently using GTX 15/50 while it runs in, and frankly for a low mileage classic I don't think the expense of a full synthetic is really worth it compared to a good quality 'standard' oil. I'll probably shift to GTX Magnatec at the next change as they are supposed to be better at controlling cold start wear which is the main issue when the cars stands for long periods. However, given the above I'm not convinced the modern oils increase leakage,
Regards
John
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I was goinf by what happened when Andy English at The Telegraph tried Fully Synthetic in his racing Aston DB5, and also what happened to a lessar extent when we ued it in an old GTi 8v. The GTi 16v loved it, but not the 8v, which still leaks oil all over the driveway but isn't worth repairing.
HJ
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Yes, if they used a synthetic with lower top end viscosity than the usual oil, then the leakage rate may well go up. The comment I made was that it isn't just the fact it's synthetic oil, it's a question of viscosity. In fact given the lower cold viscosity of modern oils this should reduce the period of high pressure following a cold start and so potentially reduce leakage!
Regards
John
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thanks for the information. As I have already aquired 25ltrs of synthetic I will fire up the MG from the beginning and see how it goes. If the driveway starts to resemble a skid pan then I will revert to your suggestion of GTX Magnatec or perhaps try a semi synthetic. Any suggestions for the gearbox which would appear to use engine oil?.
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