25 replies to this topic

[nicksuth]

I'm more of an Industrial Gearbox person (work for David Brown Gear Systems - www.davidbrown.com) so more used to heavy gear oils but I'm still pretty sure gearbox oils are thicker (higher in viscosity) than engine oils?

Quote................

Oils meeting the SAE's low temperature requirements have a "W" after the viscosity rating (example: 10W), and oils that meet the high ratings have no letter (example SAE 30). An oil is rated for viscosity by heating it to a specified temperature, and then allowing it to flow out of a specifically sized hole. Its viscosity rating is determined by the length of time it takes to flow out of the hole. If it flows quickly, it gets a low rating. If it flows slowly, it gets a high rating.

Edited by nicksuth, 24 June 2009 - 01:40 PM.

[KLAS]

Oils meeting the SAE's low temperature requirements have a "W" after the viscosity rating (example: 10W), and oils that meet the high ratings have no letter (example SAE 30). An oil is rated for viscosity by heating it to a specified temperature, and then allowing it to flow out of a specifically sized hole. Its viscosity rating is determined by the length of time it takes to flow out of the hole. If it flows quickly, it gets a low rating. If it flows slowly, it gets a high rating.

thats right, but gear oils get different numbers than engine oils
and if the engine oil flows to get a 10W, a gear oil flowing the same gets a 75W. same flowing through the hole but different number.
same without the W, engine oil flows to get rated as 50, a gear oil with the same flowing will get a 90. again same viscosity but different numbers.
so by just looking at the numbers a gear oil will always look thicker than an engine oil, but is isn't.

[Alexandre34]

So what do think of using a 5W50 (ACEA A3-B3/B4 and API SL/CF) engine oil for the Spi Mini ?

I ask you this because in France this oil can be found at Carrefour (something like Halford) and only cost 23 € (about £ 20) for 5 liters.

This oil is 100% synthetic.

[Jake Blues]

It's not so much which oil you use but the frequency you change it and the filter....often is good!

[WiredbyWilson]

i was also lead to believe that semi and fully synthetic oil causes more oil leaks due to how thin it is.

at the end of the day i still stick to using 20w50 irrelevant of cost - Rover changed the rating for later cars in order to appear up to speed with the more commonly used oils. The engines are the same and have been run on it since day one.

each to their own but gearbox failure is very costly if not terminal - thats the reason i choose to protect the gearbox in mine...

Edited by Wilson1330, 25 June 2009 - 12:47 PM.

[KLAS]

since day one? no multi visosity like 20W50 existed then IIRC they used a SAE30 at the beginning.

syntetic won't cause oil leaks, maybe it will clean away some dirt that was blocking a leak. but it won't eat gaskets.

syntetic = thin? think again, you can buy a 20W50 fully syntetic oil and this won't be thinner than the mineral one.

Rover changed to a more common oil in the mini to be more modern? and started to use an more than uncommon oil with the R65 gearbox? i don't think so. maybe a modern 10W40 could handle all the stress just the same as a older 20W50? i don't know but it could be.

[redhotmini]

they used a 10w40 because the other vehicles in the range used it too. however i would be dubious about using anything but 20w50 - its been tried and tested for many years by a hell of a lot of people so stick with that. i agree with the last comment about a modern 10w40 vs an old 20w50, but its a poor comparison, compare a modern 10w40 vs a modern 20w50 (millers CTV which is specifically desinged for gearbox in sump applications) and there will be a big difference in wear rates etc between the two.

[KLAS]

there will be a big difference in wear rates etc between the two.

you can not tell anything about the oil by looking at the viscosity exept how it flows at specific temperatures. it doesn't tell anything about everything else, like how it can handle pressure.
and to make it nearly impossible to compare, only the numbers after the W are tested at the same temp. the numbers in front of the W are tested at differend temps.

[Joloke08]

When we Originally Viewed Boris his oil was dirty and old but he drove Fantastic!!
We dont know what oil was in him and neither did the garage selling him as they never did that previous Oilchange. The Dealers agreed to flush the old oil and Change it which they did and following Autodata used 10w40 synthetic!!!!!!

Boris is Automatic and started slipping but hadnt on the test drive with the old oil,weve since changed the oil for Duckhams Q 20w50 and he doesnt slip soo much,he still slips but not quite soo much and is quieter and changes up and down more smoothly and quietly.

I really believe that any damage caused to the Gearbox was caused by the 10w40 synthetic and regardless of mk i would only ever put 20w50 mineral in a classic mini be it carb of 1959 or multi point of 2000!!!

I have a Moss Catalogue here and they only recomend 20w50 regardless of what Mk mini it is

I agree i think they only said use 10w40 because it was convienient for the dealers servicing needs but not necessarily any good for the engines!

I personally wouldnt use anything other than a quality 20w50 mineral oil i wouldnt use 10w40, definately not 10,30 and never synthetic of semi synthetic!!

I can only advise dont use anything other than 20w50 mineral im saying this from experience,if i told everybody not to put their hands in the fire and they chose to do it anyhow then its not my fault if they get their hands burnt

If you want to put any other oil in your mini engine other that 20w50 mineral thats up to you i wouldnt though!

Huggz
Jodie

[redhotmini]

automatics are notoriously fussy over oil. over time, the slipping may go away, but as far as im aware its to do with some of the additives used in more modern synthetic based oils.

[bluedragon]

On the other hand, I've used 20/50W full synthetic (Redline) on my MPI Mini for the past 3 years/20,000 miles and no problems whatsoever. It just completed a 14 day/5,000 mile journey, from sea level to 7,000 ft. altitude, from 15 to 38 degrees C, with the car running flat out for hours (especially at altitude where I had to compensate for lost power.) Only 2 -1/2 quarts oil consumed (and the oil consumption primarily coincided with the flat out stretches of driving.) No leaks whatsoever.

I suspect that it is modern oil formulation that is the problem with the automatics. Synthetics lubricate better than conventional oil, so if the automatic design requires a certain amount of "friction", then it would not perform as well. That's no different that putting the wrong grade of automatic transmission fluid into a conventional automatic box.

Most of the issues people describe with synthetics are issues that were solved 25 years ago. The only issues are those that common to all modern lubricants (reduced friction, changing additive packages) though possibly more so since synthetic is generally more slippery.

For the abuse of a Mini gearbox, synthetic has far superior resistance. Synthetic oil molecules are much more resistant to breakup from metal to metal contact that is the blender of a Mini gearbox. They are much more stable. That's why I like synthetic in a manual Mini at least.