what oil to use...what the oil company says

[DutchEdwin]

I know, a topic that has been over and over again. Everyone has it's own opinion. I thought about it and phoned the oil companies.

The companies I phoned:

BP castrol; Shell; Exxon Mobil

Only BP had a specialist phone me back on the issue. at the other companies I only got as far as the call center. I also got a good feeling about there advise.

This is what they have to say.

Be careful, it is important to know that the question I asked is about an engine that is cleaned, with new bearing, etc. The answer the oil companies gave ONLY applies to this new, cleaned state the engine is in. Not cleaned engines could result in a different advice. This question was not asked!

I have an oil filter in the engine. For engines without an oil filter the type of oil to use is different.

Here is the case I gave to them:

The question:

What kind of oil do I put in a 1955 V8 engine, totally clean inside, with new bearings. Main and rod bearing play set to 0.05mm to 0.055mm (0.0020 inch.) which is a bit larger then the original plymouth specification. the crank shaft is not hardened, new oil pump with higher oil volume then original.

The answer.

Do not put synthetic oil into this engine. The synthetic behaves different then normal oil. This type is specially developed for new type of engines with different behaviour in the gaps between the bearings etc. this means the optimal viscosity of the oil is not there in an old engine. For old engines normal oil is the best.

On my engine the manual stated 20W40. Shell and Exxon state go for this type of oil, now available as 15W40. BP has a good feeling about 15W40 but would rather go for SAE50 for better lubrication at cold start, if the car is in an mild climate area (just about freezing in the winter and mild summers). Could give you some problems of starting the engine in winter though.

All say do not go lower then SAE40.

From BP I got to talk to an oil specialist for oldtimer car. He stated that more important then pressure is oil flow. This is for cooling the temperature inside the bearing. Too high temperature means too low viscosity of the oil and too much wear of the bearing. The pressure is always measured at a point where the flow from the pump is good, some end of the big oil channel. This does not mean that the pressure is present in the bearing. He confirmed that it was wise to go for a bit higher bearing play (advised by Egge) and have a higher volume oil pump to make sure the bearings have good flow. This can be without any doubt done when the compression in the engine is as low as 7.5:1.

For our main concern, are there dopes removed from the oil (because of the environment) that can damage old engines?

Answer from all companies: The dopes in the modern oil is better then in the 50th. So modern oils will give less wear then oil from the 50th. This also applies for the camshaft and tappets. The only point of concern is the diesel engine. In the past there was sulfur in the diesel. This material also lubricated the diesel pump. On old engines this can cause problems. For the gas engines there is no point of concern.

Type of oil advised

Because the iron materials used in the 50th are not as good as now used they all advise to go for a oil type with more dopes against wear. Just to be sure. BP advised to use a oil type used in engines with more then 75k miles : CASTROL GTX 15W-40 HIGH MILEAGE A3/B3 www.castrol.com/castrol/productdetail.do?categoryId=82915476&contentId=6030822 The US type only shows 10W40. In the Netherlands 15W40 is available.

I'll take this oil because it is not expensive (28 euros for 5 liters).

My 2 cents.

[Normspeed]

I broke in my fresh motor with Castrol GTX 5w30. Then I went with Shell Rotella T 15w40. That was recommended by Jon Robinson of the DeSoto DeSpatch, a flathead guru for sure. All was going according to plan til I cracked that oil line last week and ended up doing a "roadside oil change" at Pep Boys. In order to limp home, I added 3 quarts of Chevron 15w40. Then after fixing the line, another 1 1/2 quarts of Quaker State 10w40. So now my oil is nice and clean but not what I started out with. I have great faith in the flathead six's ability to run on almost any gas or oil out there, so I'm in no hurry for another change, but when I do it will be back to the Rotella T 15w40.

[DutchEdwin]

I have to make a littel correction. I saw in the US oil link from castrol the oil they have is 10W40.

The type Castrol has in The Netherlands is 15W40.

This is what they advised me.

It sounds to me that 5W30 is to thin?