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1986 Daihatsu Skywing (flat tappet OHC) - CG-4 Oil OK in an old Petrol Engine? - edlithgow

I've acquired about 15 litres of CPC 15W40 China Petroleum Corporation (Taiwan's state-owned, I think, oil company) Superfleet CG-4 oil.

Seems a pity to waste it, but the drum doesn't appear to carry any corresponding API "S" classification.

What, if any, are the likely issues in using a diesel-only oil in a petrol engine?

For about the past 5-years I've been using a 50-50 mix of CPC SAE 40 and Mobil Delvac MX 15W40, both of which are primarily diesel oils but also show SJ. Can't get the Delvac any more.

1986 Daihatsu Skywing (flat tappet OHC) - CG-4 Oil OK in an old Petrol Engine? - Cris_on_the_gas

Cost of 15 litres of decent oil £60 - £90.

What is cost of engine ruined ?

Your choice, but I know what i would do.

1986 Daihatsu Skywing (flat tappet OHC) - CG-4 Oil OK in an old Petrol Engine? - edlithgow

Cost of 15 litres of decent oil £60 - £90.

What is cost of engine ruined ?.

Hard to say. Car is probably worth the same running or not, so in a sense the cost is zero, Replacement cost (if I replaced it) is an unknown.

Your comment, however, doesn't address the question. Here it is again, reworded

What is the probability of damage to a petrol engine from a C-spec oil?

I'd have thought it was very low, but I don't know. Perhaps nobody does, but I thought I'd post on the off-chance that somebody out there might.

1986 Daihatsu Skywing (flat tappet OHC) - CG-4 Oil OK in an old Petrol Engine? - Bolt

Not sure if this is of any help but worth a look if your interested unless you have allready seen it.

www.gulfoil.ie/lubricants/datasheets/1540-Gulf-Sup...f

1986 Daihatsu Skywing (flat tappet OHC) - CG-4 Oil OK in an old Petrol Engine? - edlithgow

Not sure if this is of any help but worth a look if your interested unless you have allready seen it.

www.gulfoil.ie/lubricants/datasheets/1540-Gulf-Sup...f

Thanks. Seems like good stuff. Very high TBN. Its not the same stuff though. Newer spec and different company. I'd guess Superfleet isn't a registered name, or Gulf's corporate lawyers aren't aware that CPC is using it.

1986 Daihatsu Skywing (flat tappet OHC) - CG-4 Oil OK in an old Petrol Engine? - galileo

What is the probability of damage to a petrol engine from a C-spec oil?

I'd have thought it was very low, but I don't know. Perhaps nobody does, but I thought I'd post on the off-chance that somebody out there might.

Here is a link to some relevant info, suggesting diesel lube oil may not be good for your petrol engine, even more so if it has a catalyst.

www.machinerylubrication.com/Read/28576/comparing-...s-

1986 Daihatsu Skywing (flat tappet OHC) - CG-4 Oil OK in an old Petrol Engine? - edlithgow

What is the probability of damage to a petrol engine from a C-spec oil?

I'd have thought it was very low, but I don't know. Perhaps nobody does, but I thought I'd post on the off-chance that somebody out there might.

Here is a link to some relevant info, suggesting diesel lube oil may not be good for your petrol engine, even more so if it has a catalyst.

www.machinerylubrication.com/Read/28576/comparing-...s-

Thanks. That's of interest, though the cat stuff doesn't apply to this car and the cold start stuff (which is viscosity-related rather than C-oil specific) doesn't apply in this climate (Taiwan). That leaves

"When you put this extra additive load in a gasoline engine, the effects can be devastating to performance. The detergent will work as it is designed and try to clean the cylinder walls. This can have an adverse effect on the seal between the rings and liner, resulting in lost compression and efficiency."

Could happen with a coked-up engine I suppose, which mine might be. OTOH I'd think it could unstick piston rings and so perhaps improve performance. Sounds difficult to predict.

With an engine in good condition (which admittedly mine might NOT be) a dramatic effect on compression seems rather unlikely.

I have, however, read "somewhere" that the over-basing necessary in diesels tends to erode tribofilms in petrol engines, which might lead to higher wear in metal to metal contact areas such as the cam lobes.

I would probably use it (IF I did) blended with CPC SAE 40 which has a base number of around 6, so that would perhaps reduce the effective overbasing of the mixture..

1986 Daihatsu Skywing (flat tappet OHC) - CG-4 Oil OK in an old Petrol Engine? - gordonbennet

Keeping in mind how old the car is, i'd use it, but i'd keep an eye on the colour of the oil via the dipstick and if it started to darken up faster than the usual oil, i'd be ready to change it sooner, and i'd be inclined to slip a new filter in between oil changes too anyway, i would assume that the Diesel oil will clean up years of baked on carbon deposits, hence not leaving the filter in too long.

I've know old hands who swore by Diesel engine oil use in their petrol engines, mainly for it's detergent properties.

An interesting aside to this, i wonder if those Diesel of Doom engine failures would have been lesscommon had specific Diesel engine oil been used instead of the current trend for oils to cover both engine types?

1986 Daihatsu Skywing (flat tappet OHC) - CG-4 Oil OK in an old Petrol Engine? - skidpan

An interesting aside to this, i wonder if those Diesel of Doom engine failures would have been lesscommon had specific Diesel engine oil been used instead of the current trend for oils to cover both engine types?

Our "diesel of doom" ran for 11 years in ours and the subsequent owners hands. We used and on my advice he continued to use the correct Ford spec oil at annual intervals (he did about 8000 miles a year). He gave up on it December 2016 when it failed its MOT on a non engine related matter. Sold it on to a chap to fix, still no MOT but still on SORN so not acrapped (just yet).

I suspect that most engine failures were caused by independents using the wrong bulk oil, even main dealers don't always use the correct stuff.

Its just plain stupid when you consider how much extra (if any extra) the correct oil is. Ford spec oil is cheap anywhere.

1986 Daihatsu Skywing (flat tappet OHC) - CG-4 Oil OK in an old Petrol Engine? - edlithgow

An interesting aside to this, i wonder if those Diesel of Doom engine failures would have been lesscommon had specific Diesel engine oil been used instead of the current trend for oils to cover both engine types?

I dunno, of course, but I'd doubt it.

I suspect (though again I dunno) that for the older spec oils that I use at least, the difference between C-only oils and dual service ones is simply that the C-only ones havn't been through the S tests, which cost money.

I'd be surprised if C-only oils are generally better in a diesel than dual-service ones.

I'd guess (again, I dunno) that it MIGHT be true for more recent specs that have DPF's etc to deal with. Since the pollution control systems are quite different in C and S engines, it might become more challenging to produce a compromise-free dual service oil, and we may see a reverse trend back to single service.