Engine oil

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rjp

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At the end of last season I dutifully changed the engine oil in my Perkins Perama M25, turned it over a few times on the starter and left it for the winter. I used a semi-synthetic oil for diesel engines from Halfords.

While browsing some old posts recently I saw some opinions that semi-synthetic or synthetic oils should NOT be used in marine diesels!

So, should I say to heck with it, run it for the season as is and accept that this might (or might not?) be a bad thing. Or should I drain it and refill with with a lower grade mineral oil? I assume that little harm will have been done over the layup season, during which the engine has not been run.

John
 
The really is one of those RTFM cases. If the manual for your engine says "mineral" or CF (the current spec, it may, like mine, say CD or even, if an older engine CC) change it. BTW these are ASME oil standards, not BS or even ISO.

What you have done will not have hurt your engine, however, a season's running my well find you with a damaged engine which will cost time and money to put right. If your engine is not designed for it, the more you use your engine with a synthetic or semi synthetic oil, the worse it will get.
 
[ QUOTE ]
At the end of last season I dutifully changed the engine oil in my Perkins Perama M25, turned it over a few times on the starter and left it for the winter. I used a semi-synthetic oil for diesel engines from Halfords.




While browsing some old posts recently I saw some opinions that semi-synthetic or synthetic oils should NOT be used in marine diesels!

So, should I say to heck with it, run it for the season as is and accept that this might (or might not?) be a bad thing. Or should I drain it and refill with with a lower grade mineral oil? I assume that little harm will have been done over the layup season, during which the engine has not been run.

John

[/ QUOTE ]

Some years ago as an experiment I ran my Renault 5 and my mower for a year on Mobil 1 [synthetic]. This caused no problem although I never expected one or I wouldn't have done the experiment. Back in the 1950's I remember talk of the dire effect of "modern" detergent oils on old pre-war car engines and there are mower maintenance men who warn you off multigrade oils and you can buy [at scandalous prices] very low spec. oils [API SA] for mowers although Honda, for instance, recommend multi-grades. Similarly, I have a 1958 MGA which I've run on current top spec. multigrade oils for 24 years so far. I admit that all of the above refers to petrol and not diesel engines but I think that talk of "damage" afflicted by synthetic oils is overdone.
 
Check the spec. American API are usually CC, CD, CF, or CF-4, though higher letters are used for car diesels with catalytic converters. Generally, higher letter oils can replace lower letter oils, although in marine diesel applications there are (arguable) advantages to having lower levels of some additives. This implies not exceeding your manufacturers spec . . .

Generally, fully synthetic oils are winter oils suitable for stop/start engines, with a very wide difference between their summer/winter SAE figures. They are designed for fuel economy, but are not very good for wear protection in prolonged running engines. It is unlikely your manufacturer would recommend it. If you've got some in the machine, best to replace it. Some mixing doesn't matter (according to Shell).

Semi synthetics may well be acceptable for a modern diesel engine. Check the spec, check your book. Their additives allow longer intervals between oil changes, but older engines, happy with a bit of sludge rolling around the system, have change intervals designed around the shortcomings of older mineral oils.

A good reference for all things oil is oil bible Although it's written around cars and motor bikes, all points lubricant are covered in great depth. Takes a bit of hunting . . .
 
I really find this post a little disturbing.

Running a Renault 5 and a mower for a year on top spec synthetic oil is one thing, but to claim that it caused NO problem without carrying out a complete engine strip before and after to examine the working parts, is hardly scientific proof. Expecialy as a mower doesn't exactly come in for a lot of use (unless you're the proprietor of a bowling club or a cricket club).

I too have an old car (in my case a '68 moggie minor). lubricating it on synthetic oil is akin to running it on Unleaded. If you do this, you must accept the damage that's being done to your engine. In a petrol engine, the insidious polishing of the bores may not be so noticeable, as it does not rely upon the compression of the mixture for ignition, but it's still happening. And as to running a '58 MGA, well a friend with a drop head minor of a similar vintage to mine did 800 miles between his last two MOTs.....mine did 8000. I use a mineral 20-50 in mine. The fact that you've used top spec oils in your MG is specious as synthetics haven't been around for 24 years.

Polished bores in Diesel engines (one effect of using synthetics in old engines) hamper compression. Modern automotive deisels are designed to operate with modern lubricants, but I'd no more put an oil formulated for petrol engines in my 3 year old diesel car than fly (unlless there was no alternative - any lubrication is better than none).

The materials modern engines are made from are a step change from those around twenty, even ten, years ago. Piston rings are no longer exclusively cast iron, bearing clearances are tighter, in fact tolerances all round are tighter. Shell bearings are increacingly disappearing from generel use. Synthetics are designed to work with these technologically advanced engines, not slack old workhorses. These days oils need special formulation for modern motorcycles (you can't use car oils in them).

I stand by what I said.

BTW, I'm a retired chartered mechanical engineer, having started as an apprentice in the 60's......so I know a liitle of what I speak.


Now I don't know when the perkins was built, or the design remit, or indeed what qualified for the description "top quality oil" when it was...which is why I gave the advice I did.
 
I know that there is a compatibility problem with mixing different oils, but can you explain what the problems are in using modern synthetic and semi-synthetic oils in older engines? The viscosity rating is the same, so what is the problem? I write as someone who knows very little about oil, hoping to get some information from someone who does /forums/images/graemlins/smile.gif
 
Marine Diesels and other special considerations.
Inland Marine Diesels (and certain road vehicles under special conditions) can, and do, glaze their bores due the low cylinder wall temperature causing the oil (and more importantly the additive pack) to undergo a chemical change to a varnish-like substance. The low temperature is caused by operating under light load for long periods.
This is related to engine design, some engines being nearly immune to it and others susceptible. The old Sherpa van diesel engines were notorious for this problem. The "cure" such as it is, is to use a low API specification oil, such as CC. Certain engine manufacturers/marinisers are now marketing the API CC oil for this purpose under their own name (and at a premium). You'll find some modern engines where its' industrial/vehicle manual states API CF and the marinised manual states API CC/CD. {Thanks to Tony Brooks for this information.}


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Marine Oils.
I sometimes get asked "why are marine engine oils so expensive and why can't I just use regular motor oil in my marine engine instead?". Well, the National Marine Manufacturers Association Oil Certification Committee (click here for more info) introduced a four-stroke engine oil test and standard called the 4T certification. This specification is meant to assist boaters and manufacturers in identifying four-stroke cycle engine oils that have been specially formulated to withstand the rigors of marine engine operation. The certification was prompted by the growing influence of four-stroke engines in the marine market and their unique lubrication demands. So the simple answer is that regular road-based engine oil products don't contain rust inhibitors and won't pass the 4T certification. Lakes, waterways and the sea is a lot more aggressive an environment for an engine to operate around than on land.
Note : the NMMA have long had a similar specification for 2-stroke oils destined for marine use, called the TC-W3® certification.

This is an extract from the Oil Bible referred to by Jim, above.
 
The first paragraph only applies to diesels left ticking over for long periods - I think that we all know this is a bad thing and avoid doing it. It doesn't address the question of mineral vs synthetic/semi synthetic.

The second paragraph only seems to relate to petrol engines.

I was hoping to get an understanding of the reasons behind your first post - are modern synthetics incompatible with mineral oils? What are the problems in using them, if any? In particular, I would like to know why there is a problem and the mechanism of the problem (if there is one), rather than just a statement to the effect that there is a problem.

From the limited research I have carried out it seems that synthetics can be exchanged for mineral oil and back again, even mixed, in virtually all cases. Earlier problems resulted from an incompatibility with certain plastics used in seals in the engines but this has apparently been overcome?

We are seeing more and more synthetics on the shelves and less mineral - the time will come when mineral is more expensive and hard to find so we need to get a good handle on the whole issue.
 
My Volvo MD22 engine (50HP) is 10 years old and basically the Perkins block, the same as used in Austin cars dating from some years ago. It's not new technology. If this describes your engine, the following inputs may be of use.

The manual requires mineral oil for the engine and fully synthetic for the separate (S Leg) gearbox. I have stuck to this over 10 seasons - all is well. But I do not use expensive Volvo oil, I prefer Castrol for car diesels, reasoning that the block has a high street not marine provenance. I purchase the oil in France - cheaper than here.

I do stick with Volvo's synthetic oil for the gear box, but source that through Keypart of Kings Langley/abroad. I am advised this oil is suitable for the stresses in a gearbox and does not have to carry pollutants in suspension, as does the oil in the sump. So the synthetic, being more durable, lasts two seasons without changing - a suitable regime, it seems.

So we keep the cost of oil as low as practical. I have never been taken by the idea that synthetic or semi-synthetic for the engine is better at resisting wear because the accumulation of pollutants in the oil (seen readily when the oil discolours after only a few hours of working) makes for early not delayed replacement. So I often change oil and filter half way through the season, to remove pollutant concentrations. I prefer to bear down on erosion of engine surfaces through frequent oil changes rather than use more expensive synthetic materials and expect them to last longer - as indeed they do.

There is one further advantage to mineral oil in the engine. Most setups are prone to water ingress from a failed gaskit or water pump etc. With mineral oil the water is bound up and produces a black butter on the dipstick - an immediate call to stop the engine and evacuate the oil, purge and fix the water ingress. Synthetic oils do not have this binding quality -water pollution will not be noticeable until damage has been done to the top gear (ouch!) and elswhere. A good reason to stick to mineral - just in iteself.

I recognise that modern higher spec engines may demand synthetic oils to prevent premature degradation of the oil and engine wear. Perkins older blocks are probably not in this category.

If this applies to your setup, in your position I would junk the oil - no damage done of course - and return to the specified mineral oil. It's prudence again....

PWG
 
Would I be correct in saying that the CD rating (which is stated for my engine) is now obsolete and that CF-4 rated oil would be the equivalent?
 
Yes. Here's Castrol's take on it: [ QUOTE ]
For those diesel passenger cars and trucks which call for API CD, API CF-4 or API CG-4, Castrol RX Super 15W-40 is recommended. Castrol RX Super 15W-40 can offer improved deposit control and wear protections for these special diesel applications.


[/ QUOTE ] Castrol rather confuses the issue by refusing to quote obsolete standards which their oils meet or exceed . . . and they don't seem to differentiate between Petrol and diesel either, which is interesting.

Ref lemain's Q about mineral oils and whether they have any inherent problems for chugging diesels. I don't know the answer, and I'm not sure anyone does. It's an arguable subject - as I hinted earlier, bit like CQR vs Spade! The questions seem to revolve around two issues. The un-necessary expense of all synthetics, and the different additives used in synthetics.

High performance synthetics are designed to match low sulphur fuels, whereas marine fuels are too often high sulphur. And some additives (good for wear) are reduced in synthetics to minimise catalyst damage - not a boat issue. Now, that's memory stuff, so unreliable. Best of luck with it!

Another argument I've heard is that synthetics are designed for tight tolerances, work well with those, but are not nearly so resistant to wear on engines with looser tolerances - the 'hammering' element. Which apparently is not just a question of viscosity.

Sorry, no sources, just ancient memories . . .
 
http://www.popularmechanics.com/automotive/how_to/4213451.html

Q: After a recent trip to two major auto parts dealers for oil (5W 30), I realized synthetic oil is slowly replacing nonsynthetic on the display shelves. The problem is, I'm getting conflicting information about synthetic oil. One store attendant told me I shouldn't go back to regular oil after changing to synthetic. Then he said it would be okay to add a quart of regular oil to synthetic, if I needed to top up. Another clerk said I should never mix the two. At a different store, the employee said it didn't matter if I used synthetic and then later replaced it with regular oil.

A: Early synthetics got a bad reputation for leaking. This was because, despite the claims of the oil manufacturers, the seal-swell characteristics of the new synthetics were different from those of the mineral oils they replaced. If the seal-swell rate was lower, the seals shrank and oil leaked from crankshaft seals and rocker cover seals. If the rate was higher, the seals swelled a little extra and the engine was tight. Then if the owner changed back to mineral oil, or added a quart when no synthetic was to be had, things got really bad. The crank seals had become worn, in their turgid state, and then relaxed. The valve cover seals were compressed when swelled, and when the different oil was added, everything leaked like, well, an old English sports car.

Fortunately, the situation has improved; you should have no problem switching back and forth. Adding a quart of mineral oil to a crankcase full of synthetic will be fine. Read the fine print — a lot of the "synthetics" on the market are blends containing a substantial proportion of mineral oil.

Then we have....

http://www.carbibles.com/engineoil_bible.html


Mineral or synthetic?
Mineral oils are based on oil that comes from dear old Mother Earth which has been refined. Synthetic oils are entirely concocted by chemists wearing white lab coats in oil company laboratories. For more info, see the section on synthetics further down the page. The only other type is semi-synthetic, sometimes called premium, which is a blend of the two. It is safe to mix the different types, but it's wiser to switch completely to a new type rather than mixing.

Synthetics
Despite their name, most synthetic derived motor oils (ie Mobil 1, Castrol Formula RS etc ) are actually derived from mineral oils - they are mostly Polyalphaolifins and these come from the purest part of the mineral oil refraction process, the gas. PAO oils will mix with normal mineral oils which means Joe public can add synthetic to his mineral, or mineral to his synthetic without his car engine seizing up. The most stable bases are polyol-ester (not polyester, you fool). When I say 'stable' I mean 'less likely to react adversely with other compounds.' Synthetic oil bases tend not to contain reactive carbon atoms for this reason. Reactive carbon has a tendency to combine with oxygen creating an acid. As you can imagine, in an oil, this would be A Bad Thing. So think of synthetic oils as custom-built oils. They're designed to do the job efficiently but without any of the excess baggage that can accompany mineral based oils.

Pure synthetics
Pure synthetic oils (polyalkyleneglycol) are the types used almost exclusively within the industrial sector in polyglycol gearbox oils for heavily loaded gearboxes. These are typically concocted by intelligent blokes in white lab coats. These chaps break apart the molecules that make up a variety of substances, like vegetable and animal oils, and then recombine the individual atoms that make up those molecules to build new, synthetic molecules. This process allows the chemists to actually "fine tune" the molecules as they build them. Clever stuff. But Polyglycols don't mix with normal mineral oils.

Mixing Mineral and Synthetic oils - the old and busted concepts
For the longest time, I had this to say about mixing mineral and synthetic oils:

If you've been driving around with mineral oil in your engine for years, don't switch to synthetic oil without preparation. Synthetic oils have been known to dislodge the baked-on deposits from mineral oils and leave them floating around your engine - not good. I learned this lesson the hard way! It's wise to use a flushing oil first.
If you do decide to change, only go up the scale. If you've been running around on synthetic, don't change down to a mineral-based oil - your engine might not be able to cope with the degradation in lubrication. Consequently, if you've been using mineral oil, try a semi or a full synthetic oil. By degradation, I'm speaking of the wear tolerances that an engine develops based on the oil that it's using. Thicker mineral oils mean thicker layers of oil coating the moving parts (by microns though). Switching to a thinner synthetic oil can cause piston rings to leak and in some very rare cases, piston slap or crank vibration.
Gaskets and seals! With the makeup of synthetic oils being different from mineral oils, mineral-oil-soaked gaskets and seals have been known to leak when exposed to synthetic oils. Perhaps not that common an occurrence, but worth bearing in mind nevertheless.

Mixing Mineral and Synthetic oils - the new hotness
That's the thing with progress - stuff becomes out-of-date. Fortunately for you, dear reader, the web is a great place to keep things up-to-date, so here's the current thinking on the subject of mixing mineral and synthetic oils. This information is based on the answer to a technical question posed on the Shell Oil website.
There is no scientific data to support the idea that mixing mineral and synthetic oils will damage your engine. When switching from a mineral oil to a synthetic, or vice versa, you will potentially leave a small amount of residual oil in the engine. That's perfectly okay because synthetic oil and mineral-based motor oil are, for the most part, compatible with each other. (The exception is pure synetics. Polyglycols don't mix with normal mineral oils.)
There is also no problem with switching back and forth between synthetic and mineral based oils. In fact, people who are "in the know" and who operate engines in areas where temperature fluctuations can be especially extreme, switch from mineral oil to synthetic oil for the colder months. They then switch back to mineral oil during the warmer months.
There was a time, years ago, when switching between synthetic oils and mineral oils was not recommended if you had used one product or the other for a long period of time. People experienced problems with seals leaking and high oil consumption but changes in additive chemistry and seal material have taken care of those issues. And that's an important caveat. New seal technology is great, but if you're still driving around in a car from the 80's with its original seals, then this argument becomes a bit of a moot point - your seals are still going to be subject to the old leakage problems no matter what newfangled additives the oil companies are putting in their products.
 
Thank you. I've just come across that information via the link from the Engine Oil Bible site and it is not desperately clear. The Castrol site does confirm that the CD rating became obsolete on 1/1/1996.

The Engine Oil Bible seems to indicate that the best replacement for older engines which need CD rated oil is CF rated oil. CF-4 is for more modern high speed four stroke engines including turbo charged engines. However, I have two Halfords diesel oil cans in my garage. The more basic mineral oil is CF-4 rated and the semi-synthetic is CF rated. This is all very confusing!
 
Use of synthetic or mineral oil is, other things being equal, immaterial as they are all hydrocarbons with similar properties. The advantage that synthetics give is that the molecular length is more tightly controlled, giving cleaner engines. Short molecules tend to burn in piston ring grooves, under piston crowns and other hotspots. Longer molecules tend to form gums in various parts of hotter engines. Consequently all oil manufacturers have olefins plants where this type of synthetic is produced. It all comes from mineral sources but the synthetics use a low molecular weight feed stock plus catalysts and some very clever techniques to produce their lubricant.

What none of the interesting downloads mention is the base number of the oil. Synthetics, by their nature, are more expensive and are therefore targeted at high perfomance vehicles, such as turbocharged trucks. The higher combustion temperatures require a high base number, perhaps 14 or so, to neutralise the combustion products in the used oil. Cooler-running engines do not need synthetics and don't need such high base numbers. One of the CC grades had a base number of 1 and CD was typically 2-3. Use of a lubricant with a high base number in a cool engine is recognised as causing bore and cam wear.

So synthetics per se do not give problems, it's the additives that do. Most boat engines run exceptionally cool - the API CC grade mentioned above was made specifically for single cylinder Bukh engines in Norwegian lifeboats. I used to use this when I could still get it, now I use API CD if possible but API CF-4 when I can't buy the CD.

I have worked for many years in research and technical services of a major hydrocarbons producer, so can claim some inside knowledge.
 
We use Castrol Tection 15W/40 in our life boat engines and they are 30 years old.
The castrol data sheet states is good for high and low temp running engines natural and turbo charged and it complies with various manufacturers criteria including Volvo. It has a base number of 11.6.
We getr it in 25 litre drums, perhaps they do some similar stuff for the "domestic" market.
Rgds
Bob
 
Castrol Tection extra is to API CJ-4. I'm sure you have researched this very thoroughly but that seems like a very high spec to me. One good point is that your 30-year old engines have probably only accumulated a couple of hundred hours, if that. An inappropriate lubricant selection is unlikely to do any damage in the short term

A problem that occurs with most lubricant producers is that they like to keep the name for marketing reasons, but the specification changes. If you were able to check the data sheets of 30 years ago, your lubricant would probably have been to CD spec whereas now it is to something else. The additive pack will have changed out of all recognition. In some cases that I am aware of, mixing current and old specifications can produce a reaction, resulting in milky layers, settlement or other problems.
 
In reply to Topcat 47's rather scornful comments I would only say that the original question from rjp was whether it would be harmful to his engine to use a synthetic oil for one season or year. I don't know how many hours that represents but in my case [VP 2002] it's about 60 hours which is much the same as my mower [30 sessions of 2 hours each] but less than the Renault 5 [ca. 200 hours]. With reference to the MGA I would never waste synthetic on it but my point was that starting with a used engine in 1983 I've always used the current best spec. multigrade mineral oil and not the straight 30 or 40 grade oils that MG parts purveyors have on offer. Incidentally, I've used unleaded petrol in that car for some years [albeit with a Broquet "catalyst" in the tank] with [I hesitate to use the phrase now] no problems so far. It's another experiment - if valve or valve seat damage occurs then it's an easy and cheap matter to repair it on that car but so far I believe that it runs slightly better on unleaded. The biggest potential flaw in my examples is that they are all petrol engines rather than diesel but my own guess would be that one season's use of synthetic would do no harm.
 
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