marki Posted January 27, 2016 Report Share Posted January 27, 2016 Afternoon All. What is the difference between Semi and Mineral oils ? Is it just down to additives ? And why do we run are engines on Mineral ? Just bored really, Mark Quote Link to post Share on other sites
Matt Posted January 27, 2016 Report Share Posted January 27, 2016 Hey Mark, Simebody will be along shortly with the right answer..... ....but while waiting.... How is the new engine performing? Matt Quote Link to post Share on other sites
marki Posted January 27, 2016 Author Report Share Posted January 27, 2016 Bloody FAB mate, money well spent. How are you ? Mark. Quote Link to post Share on other sites
john.r.davies Posted January 27, 2016 Report Share Posted January 27, 2016 Mineral is as distilled from crude oil. It contains a range of compounds of different molecular weights Synthetic is manufactured, by clever organic chemistry, and could contain molecules of a single size and weight, although they don't to achieve a range of viscosity in response to temperature. Semi(-synthetics?) are a mixture of both. But then all oils are a blend, of different fractions to achieve the desired viscosity and other properties, and the right choice is not mineral/synthetic/mix, but a good quality oil of the correct viscosity defined by the manufacturer and the temperature of the climate you live in. For a TR6 in the UK that's a 20W/50, further North (seeing -20C) 10W/30 or in very cold climates 5W/20. John Quote Link to post Share on other sites
marki Posted January 27, 2016 Author Report Share Posted January 27, 2016 Thanks John. Just what I was after. So what would stop us running a fully synthetic ? Mark. Quote Link to post Share on other sites
Don H. Posted January 27, 2016 Report Share Posted January 27, 2016 For my engine, it makes a lot more sense to run a high ZDDP mineral oil for flat tappet protection. I time-out on oil long before I mile-out on it anyway, so a super-long-life synthetic oil designed for close-clearance modern engines just doesn't seem needed for my old car. Quote Link to post Share on other sites
Eddie Cairns Posted January 27, 2016 Report Share Posted January 27, 2016 Fully synthetics tend to have the adatives for modern engines and maybe not for older engines. Therefore you would have to find a fully synthetic that is kind to older engines. Not better or worse just designed for older engines. If I remember, I think there is a Mobil1 say 10W60 or the like that will work in older engines and maybe Millers have one. Miller CLASSIC HIGH PERFORMANCE 20w50 NT Quote Link to post Share on other sites
Peter Cobbold Posted January 27, 2016 Report Share Posted January 27, 2016 Thanks John. Just what I was after. So what would stop us running a fully synthetic ? Mark. - lack of ZDDP. Quote Link to post Share on other sites
marki Posted January 27, 2016 Author Report Share Posted January 27, 2016 Hi Peter. Why do our engines need ZDDP ? Mark. Quote Link to post Share on other sites
Peter Cobbold Posted January 27, 2016 Report Share Posted January 27, 2016 Mark, It protects flat tappets from wear. Engine oil needs around 1200pm. Modern oils dont contain it, or have too little, as the phosphorous kills the catalytic convertor. List of classic friendly oils with ZDDP content: http://www.tr-register.co.uk/forums/index.php?/topic/52722-zddp-ppm-content-listing/?hl=zddp Peter Quote Link to post Share on other sites
john.r.davies Posted January 27, 2016 Report Share Posted January 27, 2016 (edited) And, Synthetics are usually 'thinner', less viscous than minerals. And moderns, built to much finer tolerances than ours do well, but it just falls out of our bearings. I tried some with a brand new - well, rebuilt - engine, and was terrified by pitiful oil pressure. Good old 20W/50 and we had 70 cold and 45 hot. The synthetic may havebeemn doing its job, but I was happier to stress it on the mineral stuff. You won't get a Synth with Zinc - it poisons the catalyst in the exhaust. John Edited January 27, 2016 by john.r.davies Quote Link to post Share on other sites
Guest ntc Posted January 27, 2016 Report Share Posted January 27, 2016 (edited) Thanks John. Just what I was after. So what would stop us running a fully synthetic ? Mark. Nowt after 5000 miles rebuilt engine? no leaks? makes mineral look daft.Edit Ring Revingtons or Opie and get the facts. Edited January 27, 2016 by ntc Quote Link to post Share on other sites
marki Posted January 28, 2016 Author Report Share Posted January 28, 2016 Hi. My engine builder is recommending Millers 15/60 synthetic, and I was after a couple of facts. Neil are you saying that Revington will also recommend synthetic ? Mark. Quote Link to post Share on other sites
McMuttley Posted January 28, 2016 Report Share Posted January 28, 2016 what's a 'flat' tappet, as opposed to any other tappet - actually, what is a tappet ! Quote Link to post Share on other sites
Peter Cobbold Posted January 28, 2016 Report Share Posted January 28, 2016 what's a 'flat' tappet, as opposed to any other tappet - actually, what is a tappet ! It rubs against the cam lobe and pushes the pushrod. Its 'flat' because its not a roller tappet. Lubrication is critical as the valve spring load forces the tappet onto the cam as it opens. Possibly the most highly stressed part of the engine. "Setting the tappet clearance" is done at the rocker arm/valve stem gap. Peter Quote Link to post Share on other sites
Peter Cobbold Posted January 28, 2016 Report Share Posted January 28, 2016 Hi. My engine builder is recommending Millers 15/60 synthetic, and I was after a couple of facts Mark. It is not listed by Millers themselves as classic friendly - page 5 here: http://www.millersoils.co.uk/pdf/automotive/Classic%20Oil%20Brochure.pdf Millers are the people to ask about suitability. Peter Quote Link to post Share on other sites
Guest ntc Posted January 28, 2016 Report Share Posted January 28, 2016 Hi. My engine builder is recommending Millers 15/60 synthetic, and I was after a couple of facts. Neil are you saying that Revington will also recommend synthetic ? Mark. Mark After 5000 miles,however your builder sounds confident ? Quote Link to post Share on other sites
marki Posted January 28, 2016 Author Report Share Posted January 28, 2016 Yes he is Neil, but now I'm thrown..... Quote Link to post Share on other sites
Guest ntc Posted January 28, 2016 Report Share Posted January 28, 2016 Mark Stick with him. Quote Link to post Share on other sites
Peter Cobbold Posted January 28, 2016 Report Share Posted January 28, 2016 http://ecx.images-amazon.com/images/I/41r1MyG6AKL._SX354_BO1,204,203,200_.jpg Quote Link to post Share on other sites
Ragtag Posted January 29, 2016 Report Share Posted January 29, 2016 Hi. My engine builder is recommending Millers 15/60 synthetic, and I was after a couple of facts. Neil are you saying that Revington will also recommend synthetic ? Mark. Having paid what, one can only assume, is a tidy sum to an engine builder to build an engine, why on earth would you 'second guess' his recommendation on the oil to use and risk invalidating any warranty you might have. Quote Link to post Share on other sites
marki Posted January 29, 2016 Author Report Share Posted January 29, 2016 Exactly.....So that's what I'm going with. I was just wondering what the main differences were. Mark Quote Link to post Share on other sites
littlejim Posted January 29, 2016 Report Share Posted January 29, 2016 Exactly.....So that's what I'm going with. I was just wondering what the main differences were. Mark Why not have a chat to the engine man about why he thinks his recommended oil is better then a high zddp oil. Quote Link to post Share on other sites
john.r.davies Posted January 29, 2016 Report Share Posted January 29, 2016 (edited) I thought that TR cam followers were slightly crowned, that there was a very large radius curvature to the face that bears on the cam. So that they more easily rotated in the bores, spreading the stress and wear over a larger area. I certain they do rotate - worn followers I've see have concentric wear marks. But recently I've been told otherwise - they are flat, no curvature at all, but that some engine designs do have a crowned follower Anyone say for sure? John Edited January 29, 2016 by john.r.davies Quote Link to post Share on other sites
Peter Cobbold Posted January 29, 2016 Report Share Posted January 29, 2016 (edited) I thought that TR cam followers were slightly crowned, that there was a very large radius curvature to the face that bears on the cam. So that they more easily rotated in the bores, spreading the stress and wear over a larger area. I certain they do rotate - worn followers I've see have concentric wear marks. But recently I've been told otherwise - they are flat, no curvature at all, but that some engine designs do have a crowned follower Anyone say for sure? John John, The geometry shows that both cam and follower have to 'slope' to get both that rotation and a decent wide surface of contact: http://www.sweethaven02.com/Automotive01/fig0349.gif If both surfaces are flat, and the follower central on the lobe, it wont rotate, so one area of the tappet wears a 'groove'. If the follower is flat and the cam tapered the force is focussed on an outer annulus and this wears faster. If the follower is crowned and the lobe not tapered it wont rotate ( if the follower is central on the lobe). Flat with flat will rotate if the center-line of the tappet is eccentric on the lobe, but that relationship is built into the block ( tappet bores wrt cam lobes) And if there's too little ZDDP - of the right type - they wear rapidly even when matched. Peter Edited January 29, 2016 by Peter Cobbold Quote Link to post Share on other sites
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