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Car Forum / MINI / May 2004another synthetic oil question
I was reading some old threads on this much-discussed subject. There are a lot of comments suggesting that synthetics are no good for mini engines or that they are too thin (or unsuitable for other reasons) for use in the gearbox. Someone suggested that the problem might be the viscosity of the synthetic oil they were referring to (eg a thin oil like 5w-30), rather than the fact that is synthetic. That possibly being the case, is there any reason why i shouldn't use a good 5w-50 or 10w-50 synthetic oil in my engine once its run-in (putting it back together this weekend), since they have the same operating-temp viscosity as a good old 20w-50 thats normally recommended? The benefits as i see them are that 1. synthetics are supposed to keep the engine cleaner, 2. have a much higher operating temperature range (so less degradation from temp extremes - not sure if this is likely to be an issue in a mini engine esp with an oil cooler fitted) and 3. are very resistant to breakdown of the Viscosity Improvers due to shearing - which would seem to be great - given the combined gearbox scenario we've got. To quote from an AMSOIL website "Multi-viscosity petroleum motor oils are more susceptible to shearing than straight weight petroleum motor oils. As previously mentioned synthetic oils are extremely shear resistant." Any more thoughts? Thanks Geoff The consensus seems to be that synthetic oil is no good for the gearbox as the high pressures mash the complex strings of molecules up and knack it. The Muffin Man > I was reading some old threads on this much-discussed subject. There are a > lot of comments suggesting that synthetics are no good for mini engines or [quoted text clipped - 26 lines] > > Geoff Yep, That's it, in the transmission casing you have a diff & gearbox that don't like synthetic, millers classic sae 20/50w will do you, using synthetic will seriously reduce the life of your transmission if you drive a mini like its supposed to be driven, been there done that, Steve68s, > The consensus seems to be that synthetic oil is no good for the gearbox as > the high pressures mash the complex strings of molecules up and knack it. [quoted text clipped - 37 lines] > > > > Geoff I hate to disagree but I don't see a consensus. There are a couple of people who claim their gearboxes were completely destroyed by one application of synthetic oil. On the other hand there are a lot more people using synthetic with no ill effects although they might not be on the list. Synthetics in gearboxes are pretty common these days, especially in motorcycles. Have a look at this URL: http://www.texassynthetics.com/hp20w50gas.htm Amsoil High Performance Synthetic 20W-50 Motor Oil Amsoil is not the best known oil in the world but they have great respect in the U.S. among racers. They are about the only oil manufacturer who even mention car gearboxes that share the engine oil. Most manufacturers, though, highly recommend their synthetics for motorcycle use. Cheers, Kelley >The consensus seems to be that synthetic oil is no good for the gearbox as >the high pressures mash the complex strings of molecules up and knack it. [quoted text clipped - 37 lines] >> >> Geoff as long as you change the oil regularly - i do mine every 3000, normal oil is perfectly adequate. muffin man is correct - the high pressures in the gbox can degrade synthetic oil. - dont bother - do your 'box and wallet a favour and go for normal 20 / 50. > I hate to disagree but I don't see a consensus. There are a couple of > people who claim their gearboxes were completely destroyed by one [quoted text clipped - 57 lines] > >> > >> Geoff > I hate to disagree but I don't see a consensus. There are a couple of > people who claim their gearboxes were completely destroyed by one [quoted text clipped - 15 lines] > > Kelley Interesting article. All I know is, I always ran my mini rally engines on synthetic (Mobil 1) and never had any reason to doubt it. Maybe I didn't drive it like it's supposed to be driven. Mind you, if I'd had to pay for the stuff I might have chosen something cheaper. I have seen a lot of gearboxes break, and broken a couple myself, but the commonest failure was diff breakage - planet gears broken and burst out through the diff casing during hand-brake turn or reverse flick, or while one wheel spinning on mud or gravel. Gross wear evident on inside of planet gear and on diff pin. Eventually the gear could rock so much on the shaft that it dug in, jammed and broke. This happened to three of our road/autotest cars running the original un-rebuilt boxes. Usually used GTX in these, never synthetic. Happened to several other competitors too. The pattern became obvious - high mileage mini boxes have serious wear in the diff, and are about to break. So after that, the first time the engine was out, I'd fit a new Minispares competition pin, and new standard planet gears and cup washers. The cost was only 20-odd quid. If you do it before it breaks, you only have to take the diff cover off. If you wait till after it breaks, there are bits of wreckage all through the engine and box, maybe in the oil pump, and you have to strip everything completely to get the rubbish out and get the holes in the casing welded up. If I'd put synthetic in and not changed those bits, the box would have broken anyway, and I might have thought the oil was crap. For comparison, I never, ever, saw any sign of wear in the corresponding parts in the rally car using synthetic oil. But those boxes had the new planet gears and new Minispares competition diff pins fitted. 2. Other failures. Seen a couple of rally cars that had repeated failures. One ran on synthetic, the other didn't. The common factor was "something came undone". A screw holding the final drive wheel to the diff came out and went through the casing. The big bolt on the end of the crank came loose and the flywheel fell off. I submit these were nothing to do with the oil. Q. Would I use synthetic in a rally car? A Yes. In a rally mini you have a constant risk of overheating, even with a big radiator and oil cooler, and especially on tight twisty stuff where you are screaming in low gears, speeds are lower and there is less airflow to keep the temperature down. Even in Scotland, it is summer for a day or two each year. It is routine for the rad to be boiling over at the end of a stage. Synthetic oils can stand higher temperatures without breaking down. That's the selling point, as far as I'm concerned. Q. Would I put synthetic in a mini road car? A. No. I'd use something a third of the price, and change it twice as often. Q. What's the best oil for any car? A. New oil. Lock. And Elvis was sitting next to Kelley Mascher in the spaceship, which I thought was kinda weird, but then they turned to me and said: > I hate to disagree but I don't see a consensus. There are a couple of > people who claim their gearboxes were completely destroyed by one > application of synthetic oil. On the other hand there are a lot more > people using synthetic with no ill effects although they might not be > on the list. Synthetics in gearboxes are pretty common these days, > especially in motorcycles. Motorcycle gearboxes are quite different from car gearboxes. They don't have synchromesh, and they don't usually have preloaded bearings. In the Mini transaxle it seems to be the baulk rings and the two large preloaded crownwheel bearings that suffer when synthetic oil is used. Seems that there are extreme point contact pressures involved with these components that exceed most synthetic oils design specifications.  SignaturePosting address is a spamtrap. Please reply to group. (-AD-) <sp4mtrap@hotmail.com> wrote in news:MPG.1b155e21228c7d61989694 @news.individual.net: > In the Mini transaxle it seems to be the baulk rings and the two large > preloaded crownwheel bearings that suffer when synthetic oil is used. > Seems that there are extreme point contact pressures involved with these > components that exceed most synthetic oils design specifications. That's the one I was waiting for :) And Elvis was sitting next to splam in the spaceship, which I thought was kinda weird, but then they turned to me and said: > (-AD-) <sp4mtrap@hotmail.com> wrote in news:MPG.1b155e21228c7d61989694 > @news.individual.net: [quoted text clipped - 5 lines] > > That's the one I was waiting for :) I've been Googling for something too, without much luck. I seem to remember that one poster involved in that long discussion wrote to an oil company (Castrol?) and posted their reply. The long and short of it was that they would not recommend any of their synthetic products for use in a Mini. They recommended one of their mineral oils of the correct grade. SignaturePosting address is a spamtrap. Please reply to group. > I seem to remember that one poster involved in that long discussion wrote > to an oil company (Castrol?) and posted their reply. > > The long and short of it was that they would not recommend any of their > synthetic products for use in a Mini. They recommended one of their > mineral oils of the correct grade. It was Steve from DSN who referred to the reply from Castrol which is on his website. I've pasted in at the bottom of this message. What you are saying is the impression i got when i first read Castrol's letter. On re-reading it, they are basically saying "yes synthetics are often thinner, but this doesn't necessarily mean reduced protection." They referred to the larger clearances in the mini engine and larger galleries etc creating reduced oil pressure on a thin oil. They finished off with saying that if you're concerned, "consider using Castrol Formula RS 10W-60 which will give rapid circulation when cold but will retain a substantial viscosity when up to its full working temperature." Castrol Formula RS 10W-60 is a fully synthetic oil. I understand from reading the AMSOIL website www.performanceoiltechnology.com that extreme pressures/shearing cause breakdown of Viscosity Improvers, which obviously reduces the viscosity of the oil. This is apparently a problem with mineral oils but NOT with synthetics. That seems though to be the opposite of what you're suggesting...??? > Check the article below of the DSN classic website (Thanks Steve), this of > course was applied to a question regarding a real Mini and not a 3 door > hatchback from a certain German Company > > We have met some concern about the use of synthetic oils, in that they have > been attributed to causing low engine oil pressure when hot. We would like > to clarify the situation. To this end, we have contacted Castrol (UK) Ltd. [quoted text clipped - 8 lines] > being designed to run on lighter viscosity oils to aid lubricant flow when > cold and provide less viscous drag when hot thereby aiding fuel economy. The > lubrication system in older engines is designed to cater for larger working > clearances on crankshaft and camshaft bearing journals, valve gear and other > moving parts, plus oil galleries will be larger and the oil pump will be of > a suitable design to pump oils of a heavier viscosity irrespective of their > base oil type. > > Synthetic oils are designed to give greater film strength and higher levels > of lubricity together with increased thermal stability and better resistance > to oxidation. They are also able to maintain their properties when used > under arduous or extreme conditions. These special properties also enable [quoted text clipped - 9 lines] > We would like to thank Castrol (UK) Ltd & DSN Classics, for their kind > assistance. Interestingly, that same reply from Castrol is on this website http://www.lotusespritworld.com/ETechnical/oil.html where they begin with "There have been some concern about the use of synthetic oils in older Esprit engines, ..., we have contacted Castrol (UK) Ltd. for their advice and this is their response:" but they didn't edit this bit "modern synthetic oils are of a lower viscosity than the A series engine was originally designed for" I didn't realise the Esprit ever used an A-series engine :-) And Elvis was sitting next to Geoff in the spaceship, which I thought was kinda weird, but then they turned to me and said: > I understand from reading the AMSOIL website > www.performanceoiltechnology.com that extreme pressures/shearing cause > breakdown of Viscosity Improvers, which obviously reduces the viscosity of > the oil. This is apparently a problem with mineral oils but NOT with > synthetics. That seems though to be the opposite of what you're > suggesting...??? Shear stress isn't the problem, extreme point contact pressure is. The clever viscosity modifying polymers in the oil that are designed to 'lock together' under pressure to locally increase the viscosity of the oil fail under extreme pressure, leaving only the light viscosity base oil to protect the surfaces. For most applications it isn't a problem - probably 99.99% of engines out there don't have components that create such point pressures. Unfortunately, the Mini transaxle does. Synthetic gearbox oils designed to lubricate gearboxes and differentials (which commonly have high point pressure components such as preloaded bearings etc.) are formulated with a much more robust base oil and are much less reliant on viscosity modifying agents. They cope just fine with extreme pressures, but of course they're not suitable as an engine lubricant. But at the end of the day it's your car - pour whatever you like into the oil filler. SignaturePosting address is a spamtrap. Please reply to group. > Shear stress isn't the problem, extreme point contact pressure is. > [quoted text clipped - 13 lines] > extreme pressures, but of course they're not suitable as an engine > lubricant. So what I said was right after all then. And there was me stressing out about how I had used 40 words instead of 4000 and got told off :D Anywhoo The Muffin Man > And Elvis was sitting next to Geoff in the spaceship, which I thought was > kinda weird, but then they turned to me and said: [quoted text clipped - 16 lines] > there don't have components that create such point pressures. > Unfortunately, the Mini transaxle does. There's no hypoid gear in the Mini, the output shafts are parallel to the crankshaft and all the other rotating elements. As a result there should be no sliding gear mesh like in a rear wheel drive diff. There obviously are still gears carrying the entire output of the motor, but thats no different to an ordinary gearbox designed to run engine oil, except of course in this case there's an engine contaminating the oil too. > Synthetic gearbox oils designed to lubricate gearboxes and differentials > (which commonly have high point pressure components such as preloaded [quoted text clipped - 5 lines] > But at the end of the day it's your car - pour whatever you like into the > oil filler. Ball bearings don't have extreme point load contact pressures. Look at the curvature of the race and this will become apparent. The contact area is fairly large especially when you take into account the normal ball and race deformation. The CWP probably has a higher contact pressure on the teeth since the pre-load on the crownwheel bearing is fairly low. The reason I say it's low is because it's being applied through the cast aluminum end cap and it's only a .001" to .004" gap depending on the year. The baulk rings and syncros seem to get chewed up no matter what kind of oil you use. I blame the driver. The people I know who use synthetic oil haven't had any increase in failures in these areas. This includes a car with a Metro turbo 1293 running a 4.13 diff and 10" wheels. If you want to compare extreme point load contact pressures, look up ASTM D4172 4 ball wear test figures for various types of oil. Cheers, Kelley >And Elvis was sitting next to Kelley Mascher in the spaceship, which I >thought was kinda weird, but then they turned to me and said: [quoted text clipped - 13 lines] >Seems that there are extreme point contact pressures involved with these >components that exceed most synthetic oils design specifications. > I was reading some old threads on this much-discussed subject. There > are a lot of comments suggesting that synthetics are no good for mini [quoted text clipped - 4 lines] > synthetic oil they were referring to (eg a thin oil like 5w-30), > rather than the fact that is synthetic. There was a big therad about this in december last year - but the person who I think posted the best answer ( about a high pressure point in the diff, if I remember rightly ) had X-no-archive in there post, so goggle groups didn't retain it :( Alas - whoever you were, please re-post :) I think it was K... something :) splam I have read heaps on why not to use a synthetic oil, but for me here is the main one....... Most, if not all synthetic oils are high in detergent. This is good for new car engines....keeps them clean. Very bad for an old engines, even one that has just been cleaned and rebuilt. All it does is strip all the old oil deposits off the internals of your motor and circulate them through it. If you want to know how this crap wears your engine, just try it. About ten years ago I made the mistake of putting Shell Helics Race oil in a newly rebuilt Cooper S engine.....well it WAS the most expensive oil I could buy...... so it should give the best protection!! Got 5000 Km out of the motor and it had to be striped, reringed, and bearinged. I WON'T make the same mistake again. Use a good quality oil, and change it regularly. Craig > I was reading some old threads on this much-discussed subject. There are a > lot of comments suggesting that synthetics are no good for mini engines or [quoted text clipped - 26 lines] > > Geoff An engine will last more than 3000 miles, regardless of what kind of oil you use, mineral or synthetic or vegetable. As long as you clean out the oil galleries after the last blow-up, as long as you don't reuse an oil cooler that is full of swarf from the last blow-up, as long as your oil pump is ok. I once had an oil pump rotor break up, but that was on a high mileage 1300GT using GTX. I once bought a pump that wouldn't turn freely by hand. Took it back to the BL garage and swapped it for one that worked without clonking and grinding noises. I don't think the oil killed your engine. All oils have detergent. Lock. > I have read heaps on why not to use a synthetic oil, but for me here is the > main one....... [quoted text clipped - 51 lines] > > > > Geoff |
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