Which engine oil

[TWF]

Hi, I am just in the process of rebuilding my V8 250 engine ,regrind ,bearings , re bored and new pistons , with all the advancement in engine oils over the last 60 or so years , which brands / grades of oil are current owners of SP,s and Saloons using? Regards ,Terry .

[tjt77]

It is partly dependant upon your location and what oils are readily available... if everything is clean and fresh i'd recommend an oil designed for fleet diesel engined vehicles.. this is due to economics and commonsense applied to the known characteristics of these engines....I personally use 15w/40 Shell rotella/Mobil delvac/chevron delo 400 ...whichever is in stock at the discount supplier.. these are high spec oils for turbo diesel engines..so good for high loads and they have the anti wear additives that commonly USED to be in engine oils for cars.. and they have sufficient detergent for engines that produce high carbon deposits in the oil. (something the turner V8 is famous for) Id advise against 'normal' oil specified for modern car engines..party because of the loads imposed and metallurgy employed in 'our' engines requires the old additives such as ZDDP..
you can also use specialist oils for classic car engines.. originally these engien's were designed to use 30w oils in 'normal' northern european climates.... and then the common choice when multigrade become de rigeur was 20w 50.. avoid any oil with cold viscosity below 15w.. 15w 40 is ideal in my opinion.. 20w 50 would be the second choice.. for engines with known wear (detectable blow-by and less then 40lbs oil pressure @ 2800 rpm when fully hot) go with a a classic car engine oil that is 20/50 or minimally 30w if using non multi grade..

[Jez]

The previous post rightly identifies the need for higher levels of ZDDP in the oil for the Turner V8 and indeed most engines of that era. It's not as simple as more is better either - there's a lot of science behind the formulation of oils and more than a little hocus pocus on some other (inferior ) internet forums. I'm not familiar with the make up of the oils for modern diesel cars, but certainly reputable brand oils, e.g. Castrol, Penrite, Millers etc, all have the necessary additives in their oils designed for classic engines.

Personally I have Castrol 20/50 in the SP250 and MGB, but would be equally happy with Penrite / Millers etc.

Cheers - Jez

[Phillmore]

Penrite produce a high ZDDP oil which I use in the Conquests.

[Sydsmith]

What ever happened to molybedenum di-sulphide? (pardon the spelling)

[smithgor]

When I bought my SP250 last year the engine had recently been rebuilt by Russ Carpenter so I asked him what oil I should use when I came to change it at 2yrs.
The answer wss to use a "classic 20/50 engine oil, Halfords do a classic engine oil by Duckhams, I use Morris’s classic 20/50 but don’t use a modern synthetic oil, they have a tendency to gum up the rings and valves"
I'll be following his advice.

[David S]

Doesn't the viscosity of the oil depend on the mesh size in the filter?
I say this because I have a Flexolite 'spin-on' adapter and I always feel the oil thickness should match the filter's mesh.
The filters are for modern car's oil so it should keep the oil clean in the Dart?

And in relation to your question, I have started to use 20-50 Morris Oil oil and change it ,ore regularly than the spec.

David

[Jez]

Choice of viscosity is largely down to clearances in the oil pump and engine bearings, plus operating temperature. If we assume normal road use, then high temperatures (requiring thicker rated oils to maintain the same viscosity at the higher temperature) can be ignored. Modern engines have tighter tolerances and use thinner oils to achieve reduced drag, but in our engines that risks reduced oil pressure and increased bearing wear.

Choice of oil filter should then follow choice of oil. In practice, standard car filters we will fit to our cars are tolerant enough not to worry. A finer grade of filter and thicker oil will wear or clog the filter a bit more quickly, but the combination of higher oil / fuel quality, typically low mileage and annual changes it's not a practical issue.

Cheers - Jez

[tjt77]

the issue of oil pressure is brought up above.. it seems the SPs (at least the ones Ive owned) run higher oil pressure than the saloons..typically those I have owned ran around 50-60 lbs at cruising speeds and have much longer engine life than saloons in 'normal' circumstances.... due to the fact the saloon engine has to work harder ( more weight allied too much lower gearing) one should take into account that the standard 'recommendation' for oil pressure is 10lbs per 1000 rpm.. given the saloon is factory setting oil pressure relief valve is @ 45lbs.this is inadequate for brisk use.. @ cruising speed the engine will be spinning 3,500 rpms + and a burst up to 5,000rpms is normal.. max power is achieved @ 5,800 rpms..at which speed 45lbs of oil pressure is insufficient..(most of em out there stuggle to reach 40 lbs when hot) which is one of MANY reasons the saloons tend to lunch their intermediate main bearings before the car has covered 50 k miles..
oils... for my part, since i drive my cars frequently and cover large mileages, economics has to be factored in ..hence I seek out products that are high quality but priced economically.. the common turbo diesel engine oils have all the required additives and represent the best value for a suitable for this application high quality oil.... unsure of Uk prices, but I pay approx $18 -$22 per US gallon for either Shell rotella or chevron delo 400..(depending on supplier chosen) which is generally changed at between 4 and 5,000miles..(i also run a modern 'spin on' filter and added an oil cooler..something I consider 'essential' in temps where i reside) the 'hack' has apporx 65k miles on its last engine rebuild.. still shows 55lbs of oil pressure @ 3,000 rpms fully hot..and temp guage in middle on +/-95oF days running on 15w 40 multigrade..Im sure it would read the same on 20/50 oil.. ( BTW.. a 50 weight oil is thinner at full operating temperature than a 40 weight ... a 20/50 multigrade is equiv to 20w when cold and has HOT viscosity of a hot 50w.... thicker oils thin out more than lighter oils when fully hot..)

[Phillmore]

I would have thought 45 lbs at any revs would provide sufficient lubrication. That is a good (hot) oil pressure on any engine surely. Pressure is the effort required to push the oil where it needs to go and at that pressure it will get there and do it's job.