question Best type of oil

[gas 44]

Hi,getting closer to getting Jacks old GMC back together and back on the road.

Really wanted to change the oil,so can anyone suggest the best type,as we are not sure what grade (other than the cheapest ) is in there now.

Thanks in advance

 

Gary

[Tony B]

Valvoline or Halfords classic, 20/50. Valvoline is slightly more expensive. I've used both in the Dodge with no problems.

[Degsy]

Valvoline or Halfords classic, 20/50. Valvoline is slightly more expensive. I've used both in the Dodge with no problems.

 

Best to stick with the original straight 30 grade.This has been discussed several times on here and although some people do use 20/50 for a number of reasons the general consensus came down in favour of a good quality 30 grade. Have a look at Morris Oils website they have specially formulated oils etc for older vehicles.

I have used their stuff for years in both old and modern vehicles with no problems.

[oily]

Morris Lubricants SAE 30 Golden Film Classic Motor Oil...... £57.80 for 25ltrs Bargain:-D

[gas 44]

Thankyou for your input gentlemen,looks like 30 grade it is,how often should this type of oil be changed and does it require a filter change each time.

 

Gary

[Lewis Garner]

we buy our 25 litres of the golden film here in bedfordshire for 52.80 inc. the vat from barton fuels and lubes in oakley. they're very helpfull guys

 

regards lewis

[Degsy]

Thankyou for your input gentlemen,looks like 30 grade it is,how often should this type of oil be changed and does it require a filter change each time.

 

Gary

 

It depends very much on your usage and mileage, could I recommend you join the CCKW forum, everything you need to know about your GMC can be found on there.

Bill who owns the forum is also a member on here, he posts as 'weasel nut' and I am sure you will find Bill and the forum very helpful.

[N.O.S.]

The main thing to bear in mind is that the straight oil works by dropping the big nasty bits into the sump where they can lie harmlessly - the bypass filter gradually takes out the finer nasties (it only filters a very small proportion of the oil flow). This is why with older engines they recommend to remove the sump periodically and clean it.

 

Whereas -

 

A modern mutigrade engine oil is formulated to carry the particles around in suspension so everything gets pulled out each circuit by the full-flow filter. Without this filtration (as in older engines) these particles will continue to circulate around through bearings etc.

 

Mainly in the (misguided?) belief that 15W cold behaviour would allow easier cranking for starting and 40W hot behaviour would give a strong oil, I've used 15/W40 in a GMC for almost 20 years. You'd only get the starting benefit in cold winter temperatures when she doesn''t come out much anyway. Until now the truck hasn't done the high the high mileages or long trips that some GMCs do.

 

I've come to the conclusion that for our level of use I don't really think it matters which oil you use. But I thought if they were designed for straight oil, and the modern multigrades give no advantage, then why not use straight oil?

 

So - and thanks to your question prompting me to think about it again - last week I changed the GMC oil to Morris straight 30

[Degsy]

NOS, you know it makes sense.

[Tony B]

Yes boys, but if as you say it dosen't seem to matter which oil is used. Why not use modern oils such as 20/50? One thing I did take away from college, Good oil and grease are cheaper than repairs. Lubricants have come a long way. I can even vaguley remember the first TV adverts lauding the qualties of Q20/50 motor oil, which ever make it was.

[Degsy]

Yes boys, but if as you say it dosen't seem to matter which oil is used. Why not use modern oils such as 20/50? One thing I did take away from college, Good oil and grease are cheaper than repairs. Lubricants have come a long way. I can even vaguley remember the first TV adverts lauding the qualties of Q20/50 motor oil, which ever make it was.

 

Are you trying to say that just because it is a 30 grade it is not a modern oil?

I suggest you go to Morris Lubricants website and spend some time reading all the info on there, you might then understand why so many people recommend using their product.

The oil manufacturer you are trying to remember was Duckhams.

[Tony B]

30 Grade has it's properties, 20/50 has diffrent. Otherwise there wouldn't be two types.

'multigrade' oils were introduced to cover a greater range of use peramiters than a straight grade.

So why not use it? Oil has a lot more work to do than just lubricate, as you will be well aware.

For what I use my Dodge for, and that I change oil twice a year regardless of work done, just an old habit, I find 20/50 easily available, relativly cheap and performs well. All old oil goes down to the local recycle bin.

 

Duckhams, oh yes, Duckhams Q20/50 for some reason I thought it might be Esso, probably because of the 'put a tiger in your tank ' TV ads, theres a tale there as well.

Edited July 15, 2010 by Tony B

[N.O.S.]

30 Grade has it's properties, 20/50 has diffrent. Otherwise there wouldn't be two types.

'multigrade' oils were introduced to cover a greater range of use peramiters than a straight grade.

So why not use it? ........ For what I use my Dodge for, and that I change oil twice a year regardless of work done, just an old habit, I find 20/50 easily available, relativly cheap and performs well.

 

I put multigrade in 20 years ago because I liked the fact that when cold, a 15W40 behaves like a 15 weight oil (thinner than 30) so allows quicker spread of lubrication and easier starting (especially with 6v!!), and when hot, the 40 weight (thicker) properties give better load carrying in bearings.

 

My decision to change to straight was based only on the realisation that the straight grade oil is better suited to the type of filtration found on a lot of these older engines. With bypass filtration the oil might circulate many times before a visit to the filter, so anything it can offload in the sump in the meantime must be good for the engine.

 

If this thread had not been started I would probably now have fresh mutigrade in there. And as you say given the use, I'm sure I wouldn't notice any difference either way for 20 years or so :-)

 

If an engine is generally worn and has worked fine for a long time with a particular grade of oil I wonder if it might be better to stick to that grade rather than change, as bearings will have bedded in to suit the lubrication pattern of that grade - changing might alter the lubrication pattern which could cause accelerated wear and premature failure.

 

If it works - don't fix it :cool2:

[Richard Farrant]

If an engine is generally worn and has worked fine for a long time with a particular grade of oil I wonder if it might be better to stick to that grade rather than change, as bearings will have bedded in to suit the lubrication pattern of that grade - changing might alter the lubrication pattern which could cause accelerated wear and premature failure.

 

If it works - don't fix it :cool2:

 

 

Hi Tony,

 

If you have a vehicle of the older type with bypass oil filter, then a classic type monograde is the best type of oil to use, especially if you do not know what has been in it before. The danger is changing the oil on an engine which has been running on non-detergent ( or very low) oil for considerable time, there will be sludge or sediment laying in the lower parts of the engine. Changing it to a modern multigrade with high detergency, will scour the sediment and distribute it through the system, but not having a full flow filter, it will probably contaminate the bearings, if not block the oil ways. So if in doubt, go for a classic monograde. Be wary of diesel monogrades as they will have a high detergency as well.

Edited July 15, 2010 by Richard Farrant

[Tony B]

Thanks Richard, I'm in the fortunate position of having a very low milage engine, it was changed in Norway, acording to the plate 1963. To my knowledge it has run on 20/50 since restoratin. I agree muck is the enemy. Katy the WC54, I'll probably run her on 30 grade, trouble is she has been sitting for nearly two years, I'd welcome to any advice on how to treat her engine. It runs OK, but sitting can't help. I'd like to flush everything through.

Whatever oil it is the engine management system, Brain and right foot. I treat an engine like a horse, always take things nice slow and steady for the first mile, to warm up. And the same for the last mile to cool down!

I ran her from Auchonvilliers one year up to the ferry, 30C + air temprature. Took about three hours. Oil pressure and temp were fine when running but as soon as I reached the port and idlied, down oil- up temprature! I just left her idle for about five minutes till everything read normal before shutting down.

[N.O.S.]

I'd forgotten all about the Fairy Liquid effect, Richard!

[Degsy]

Hi Tony,

 

If you have a vehicle of the older type with bypass oil filter, then a classic type monograde is the best type of oil to use, especially if you do not know what has been in it before. The danger is changing the oil on an engine which has been running on non-detergent ( or very low) oil for considerable time, there will be sludge or sediment laying in the lower parts of the engine. Changing it to a modern multigrade with high detergency, will scour the sediment and distribute it through the system, but not having a full flow filter, it will probably contaminate the bearings, if not block the oil ways. So if in doubt, go for a classic monograde. Be wary of diesel monogrades as they will have a high detergency as well.

 

I rest my case. Thanks Richard.

[trustmeimamechanic]

Just to add to the general chat..... some modern oils also contain addatives that will attack older type oilseals and also bronze bushes and bearing surfaces , both in your engine or if using modern EP type gear oils in your gearbox and diff.

I just paid for some Morris oil for my Jeep gearbox even though I have gallons of free EP90 in my shed :-D

[Tony B]

I rest my case. Thanks Richard.

 

Ah yes, but, if the engine is properly maintained and the oil changed regularly. When does the muck get a chance to build up? :cool2: