Yanmar 2GM20 Oil

[Daverw]

Hi, I’ve been looking at past threads on this and most are old and not very conclusive, what oil are people using for the 2GM20, both engine and gear box, manual appears to suggest the same in both but they s seems to be a little strange.

Would like simple answer if possible not deep technical one

 

[Tranona]

Simple answer is a 15/40 mineral oil to CF spec. for both, just as it says in the manual. Usually sold in car parts shops and supermarkets as suitable for older type diesel engines in cars/vans.

 

[Daverw]

Thanks for a simple answer

 

[Kelpie]

You'll need to check the spec on your gearbox- some engine/gbox combinations are happy using the same oil. My 3GM30 uses SAE30 in the gearbox and 15W40 in the engine. As Tranona says, don't bother with fancy synthetic oils, they are designed for modern high compression engines which operate at different temperatures etc.

 

[JumbleDuck]

Thanks for a simple answer

The official spec, CD, is still available, but normally only online. As Tranona says, CF is the usual replacement.

These engines like cheap and nasty oil in 'em. I had though force of circumstance to give m 1GM10 some semi-synthetic, and it hated it. Oil consumption went from "negligible" to "refill every two hours" and only calmed down a bit when I got some CF into it. It took a lot of running on CD to bring things back to acceptable, though.

 

[richardabeattie]

Could we have a couple of brand names for "15/40 mineral oil to CF spec"? What does CF stand for?

 

[PaulRainbow]

CF isn't as easy to find as it was, because it's been upgraded to CH. This stuff is perfectly fine for those older diesels requiring 15/40 mineral oil and doesn't have a marine price tag :

https://www.eurocarparts.com/ecp/p/...ineoils/15w40-engine-oil/?521776101&0&cc5_246

 

[earlybird]

"C" stands for diesel. "F" stands for latest type. Put together they mean cheapest that you can find. Got my last can from Halfords. Supermarkets no-longer seem to carry it in stock as much as they used to.

 

[lpdsn]

Hi, I’ve been looking at past threads on this and most are old and not very conclusive, what oil are people using for the 2GM20, both engine and gear box, manual appears to suggest the same in both but they s seems to be a little strange.

Would like simple answer if possible not deep technical one

If you have the manual may as well go with its recommendations. The Yanmar manual for my engine specifies a particular ATF for the gearbox, but the gearbox isn't by Yanmar themselves.

 

[lpdsn]

"C" stands for diesel. "F" stands for latest type. Put together they mean cheapest that you can find. Got my last can from Halfords. Supermarkets no-longer seem to carry it in stock as much as they used to.

Amazon is a pretty good source. I get CD from them.

 

[sailorman]

"C" stands for diesel. "F" stands for latest type. Put together they mean cheapest that you can find. Got my last can from Halfords. Supermarkets no-longer seem to carry it in stock as much as they used to.

"C" stands for Compression

 

[JumbleDuck]

Amazon is a pretty good source. I get CD from them.

I usually get my oils from Smith and Allan, who sell direct, on Amazon and on eBay - carriage free on eBay. I don't know if they have a CD, but they do have a CF-4: https://www.smithandallan.com/produ...892-smith-and-allan-ultra-15w-40-engine-oil-/

 

[vyv_cox]

Could we have a couple of brand names for "15/40 mineral oil to CF spec"? What does CF stand for?

API CF to give it its correct designation, one grade of oil in a whole raft if them to cope with different operating regimes, fuels, engine power, etc. There is a page about it on my website.

 

[RichardS]

These engines like cheap and nasty oil in 'em. I had though force of circumstance to give m 1GM10 some semi-synthetic, and it hated it. Oil consumption went from "negligible" to "refill every two hours" and only calmed down a bit when I got some CF into it. It took a lot of running on CD to bring things back to acceptable, though.

As you'd expect, my experience is different.

There is nothing intrinsically beneficial about "cheap and nasty oil" ...... except that it is "cheap" and that it comes readily available in the higher viscosity ranges that older engines were designed around. I cannot believe that there will ever be a benefit in searching out "nasty" .... except perhaps in connection with a certain type of occasional companion.

Certainly using an oil which is much thinner, and synthetic oils are often much much thinner, will increase oil usage but a synthetic oil of the correct grade is very likely going to be better than anything "cheap and nasty", although there is a cost-benefit analysis to be done.

 

[vyv_cox]

The chief difference, as detailed on my website, is the additives. There is no intrinsic difference between synthetic and mineral base oils, in fact the synthetic has a far narrower range of molecular weights than the mineral, which results in a cleaner engine. The additives are a different matter though and some are only active at the high loads and temperatures for which they were designed. Outside these they may offer no benefits and maybe do harm.

 

[JumbleDuck]

There is nothing intrinsically beneficial about "cheap and nasty oil" ......

I think it resists bore glazing better. Or, to put it another way, I think that using synthetics in an engine which doesn't expect them can promote glazing. To take an extreme example, running-in oil is still available for older cars.

Otherwise I agree that modern oils are generally better - my DS runs very happily on 10-40 semi synthetic.

 

[RichardS]

The chief difference, as detailed on my website, is the additives. There is no intrinsic difference between synthetic and mineral base oils, in fact the synthetic has a far narrower range of molecular weights than the mineral, which results in a cleaner engine. The additives are a different matter though and some are only active at the high loads and temperatures for which they were designed. Outside these they may offer no benefits and maybe do harm.

I agree that there is a cost-benefit analysis to be done .... and if you change your oil at the end of every season irrespective of mileage/hours, then the cost-benefit is going to be heavily loaded towards cheap oil.

As you know, I've never found any harm being created in older engines by using semi or fully synthetic but have always been amazed by how clean and carbon-free the engine remains internally and that's enough to weigh the analysis over to the benefit side for me. However, older engines do need to be run-in with mineral oil (see JD's point), although they always have been by now, and the oil must be the correct grade.

Richard

 

[vyv_cox]

I agree that there is a cost-benefit analysis to be done .... and if you change your oil at the end of every season irrespective of mileage/hours, then the cost-benefit is going to be heavily loaded towards cheap oil.

As you know, I've never found any harm being created in older engines by using semi or fully synthetic but have always been amazed by how clean and carbon-free the engine remains internally and that's enough to weigh the analysis over to the benefit side for me. However, older engines do need to be run-in with mineral oil (see JD's point), although they always have been by now, and the oil must be the correct grade.

Richard

I run my Lomax on semi-synthetic, based on 1979 2CV engine. It has no cooling fan, air cooled of course, so tends to get quite warm. Ideal application for non-mineral oils.

 

[dom]

I agree that there is a cost-benefit analysis to be done .... and if you change your oil at the end of every season irrespective of mileage/hours, then the cost-benefit is going to be heavily loaded towards cheap oil.

As you know, I've never found any harm being created in older engines by using semi or fully synthetic but have always been amazed by how clean and carbon-free the engine remains

Owning a Yanmar I decided to ask BP's advice on this and the use of road diesel which includes a percentage of FAME. Wrt FAME, BP's answer was as clear as day and I have previously summarised and posted the reasoning.

In terms of engine oil, their advice was that modern engines are very different to older ones, operate at finer tolerances, higher temperatures, etc. The message was that the use of synthetic "may or may not" do harm, and that this would be difficult to determine ex ante in the absence of a detailed discussion between the oil co. and the engine OEM. Moreover, their advice was that if the engine specified regular changes of 'low spec' oil, then one should do that and not be influenced by the 20,000 oil change interval on modern cars.

It would therefore seem that the question is less one of cost-benefit analysis and more one of:

"Do you feel lucky punk ....well do ya?" ​

 

[RichardS]

I run my Lomax on semi-synthetic, based on 1979 2CV engine. It has no cooling fan, air cooled of course, so tends to get quite warm. Ideal application for non-mineral oils.

Indeed. My Son's Series 3 Landy is, by far, the oldest engine we have in the family, and we've been running it on semi-synthetic but we've now been able to source 20W-50 fully synthetic for a good price for 10L so, once the rebuilt is complete, we'll be switching to that.

Richard