Which oil?

sailorman said:
20>50 will make starting in cold weather more difficult with the thicker oil, 15>40 is thinner viscosity @ lower temps
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Agreed. In fact the only reason to use a 0W40 oil is if you are hand starting. Putting this stuff in allowed me to hand start my MD1. I did thousands of miles over 10 years with no problems using Mobil 1 but as I said earlier Asdas cheapest for me now I have a big one
 
Oil research organisations use engines with weaknesses in certain areas to investigate effects and improvements in various oils. Triumph Dolomite engines have an unusually low big-end bearing length to diameter ratio (i.e. very narrow) and were (are?) used to investigate factors that affect oil film thickness in this location. I recall a report in which these engines were run at maximum revs for 60 hours. On 20/50 oil the test was completed and no wear was detectable. On 15/40 some bearing and journal wear was detected but was considered satisfactory. On 5/40 the engine blew up after some hours due to a big-end failure. 0/40 did not exist at that time.

An extreme test but a good lesson.
 
sailorman said:
15>40 as its readily available from most supermarkets & factors
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Yes. As Sailorman says, widely available and perfectly suited. I have used this grade in a series of vehicles for many years, in temperatures down to -20C without any starting issues. As I wrote earlier, for older engines with some bearing wear a 20/50 might be better.
 
vyv_cox said:
Oil research organisations use engines with weaknesses in certain areas to investigate effects and improvements in various oils. Triumph Dolomite engines have an unusually low big-end bearing length to diameter ratio (i.e. very narrow) and were (are?) used to investigate factors that affect oil film thickness in this location. I recall a report in which these engines were run at maximum revs for 60 hours. On 20/50 oil the test was completed and no wear was detectable. On 15/40 some bearing and journal wear was detected but was considered satisfactory. On 5/40 the engine blew up after some hours due to a big-end failure. 0/40 did not exist at that time.

An extreme test but a good lesson.
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OUCH!! That sounds like a cruel test! Was that at full throttle as well as full revs? Also, presumably, it was the "40" that did the damage, rather than the "5"? I'm still not sure I have my head round this, but am I right in thinking the "5" is only really relevant until the engine is warmed up to operating temperature and once there, the "40" (or 50) is what's important?
 
Avocet said:
OUCH!! That sounds like a cruel test! Was that at full throttle as well as full revs? Also, presumably, it was the "40" that did the damage, rather than the "5"? I'm still not sure I have my head round this, but am I right in thinking the "5" is only really relevant until the engine is warmed up to operating temperature and once there, the "40" (or 50) is what's important?
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The way to get your head round it is to know where the numbers come from.
What happens is they put a sample of the oil in a container with a small hole in the bottom and time how long it takes for the oil to run out. This gives a number so it is common to have oil rated in seconds ( e.g. very thick oil used in power stations can be refferred to as 3500 second oil where as diesel may be 35 second oil.
Now on the above tests the oil is at a standard temperature but on lube oil you want it be be relatively thin when its cold and thick when its hot. To achieve this they have developed multi grade oils. That means they act thin when cold and thick when hot.
When they are talking 20W50 they mean its like a 20 second oil when cold and a 50 second oil when hot.
When they say 15W40 they mean its like a 15 second oil when cold and 40 second oil when hot
So ideally its as thin as possible when cold (low first number) and thick when hot (high second number)
Experience shows it is sometimes best not to use the thinnest available on older engines
Hope this helps
Martin
 
superheat6k said:
I use Shell Rimula 15W40, no probs with it. As long as the oil is CF spec or higher then that should be fine.
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Care is needed when considering Shell products by name. Rimula has been around for very many years, with its specification changing from time to time. It was originally a fairly low-tech general lubricant but is now quite different. One of the biggest changes I know of is with Tellus hydraulic oils, which at one time carried no additives and were widely used for mechanical seals. Tellus is now a totally different product with high additive loading and duties that worked with it perfectly well now run into problems.

Also, using oils with specifications higher than API CF is likely to give problems with old engines. There is a good deal about this on my website, but also on almost every classic, vintage or veteran car, truck and tractor website that you can find.
 
Halo said:
The way to get your head round it is to know where the numbers come from.
What happens is they put a sample of the oil in a container with a small hole in the bottom and time how long it takes for the oil to run out. This gives a number so it is common to have oil rated in seconds ( e.g. very thick oil used in power stations can be refferred to as 3500 second oil where as diesel may be 35 second oil.
Now on the above tests the oil is at a standard temperature but on lube oil you want it be be relatively thin when its cold and thick when its hot. To achieve this they have developed multi grade oils. That means they act thin when cold and thick when hot.
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Thanks Halo,

OK, so I can see that a straight 30 oil (say) would take (say) 30 seconds to run through the cup at the standard temperature?

Here's where it all goes wrong for me though;
Halo said:
When they are talking 20W50 they mean its like a 20 second oil when cold and a 50 second oil when hot.
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Ok so does that mean that when cold (say, 10 degrees?) it behaves like a 20 second oil would when the 20 second oil is at the standard temperature, or when the 20 second oil is at 10 degrees? And similarly, when hot (say 100 degrees) it behaves like a 50 second oil would at the standard temperature or like a 50 grade oil would at 100 degrees? Having watched it drip off the dipstick when hot, I'm assuming it's the latter in both cases, as it seems much thinner than at room temperature!
 
vyv_cox said:
Care is needed when considering Shell products by name. Rimula has been around for very many years, with its specification changing from time to time. It was originally a fairly low-tech general lubricant but is now quite different. One of the biggest changes I know of is with Tellus hydraulic oils, which at one time carried no additives and were widely used for mechanical seals. Tellus is now a totally different product with high additive loading and duties that worked with it perfectly well now run into problems.

Also, using oils with specifications higher than API CF is likely to give problems with old engines. There is a good deal about this on my website, but also on almost every classic, vintage or veteran car, truck and tractor website that you can find.
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Vyv, I use Shell Rimula R4 (which seems to be the latest Rimula variety to find its way to Turkey, as I previously had R3 which is no longer about. I think R4 meets specifications from CF up to CJ. My engine is a more modern 1998 turbocharged Yanmar 4JH series with about 5,000 hours on it. The engine seems fine on that oil. Am I likely to be doing it any harm, or have I made a good choice? Also would Rimula R4 be OK in an older engine like a Thorneycroft?
 
Norman_E said:
Vyv, I use Shell Rimula R4 (which seems to be the latest Rimula variety to find its way to Turkey, as I previously had R3 which is no longer about. I think R4 meets specifications from CF up to CJ. My engine is a more modern 1998 turbocharged Yanmar 4JH series with about 5,000 hours on it. The engine seems fine on that oil. Am I likely to be doing it any harm, or have I made a good choice? Also would Rimula R4 be OK in an older engine like a Thorneycroft?
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R4 looks good to me. The CI-4 and CJ-4 specifications, although aimed at ultra-low sulphur levels, keep a relatively high TBN due to higher acidity caused by exhaust gas recirculation. This is not ideal for yacht engines that rarely achieve high temperatures and therefore high acidity. An earlier spec might be better, but their TBN is higher to cope with higher sulphur in the diesel fuel. You can't win!

An elderly Thorneycroft, maybe 1970s or 80s? would be better on an oil from its era. I use an API CC in my BMC 2.2 diesel, bought from Morris Lubricants, who will deliver. Both these engines are widely used in canal barges so it's quite a big market and availability is good.
 
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