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MG MG Y Type - too high oil pressure after oil change

What could be the reason of a very high oil pressure after an oil and -filter change? The filter is the later horizontal type.

The pressure was in the 30-50 PSI range and now 70-80 PSI. Obviously something is not OK, but what?
Willem vd Veer

What grade oil are you using now as opposed to before?

Did you change the filter too, and if not how much did you put in?

You could have put too much oil in and over filled it if you didnt allow for the oil left in the filter system (about a pint and a bit - dont know what that is in funny metric stuff though) and that could be causing it too possibly.

Paul
Paul Barrow

Ít did not happen to my car.

The oil is a thicker Pentrite 20W60
The filter was changed
Dont know about overfilling.

We are suspecting the pressure relief valve, which will be inspected soon.
Willem vd Veer

Recommended is 20W/50

I would suggest drain and replace with 20W/50 Willem.

I think 20W/60 is much thicker and I dont know what that will do in terms of putting a load on other components. As the 20W/60 will have pluged into the filter I would also replace that too now.

Recommended Penrite oil is their HPR30 - see the Penrite page.

These are just my thoughts but I am not a Tribologist.

Paul
Paul Barrow

Paul,
I have a TD which I run with penrite 20w/60. I used to use penrite 20w/50 but found the pressure dropped by 15psi to 25psi when cruising on the motorway at 60mph with a 5 speed box at 3200 rpm.

On changing to 20w/60 I find the oil pressure is the same when cold but does not drop off when the engine is hot it stays at around 40 to 45psi.

I would therefore suggest the increase in pressure cold is not down to the different grade of oil.

regards Chris
C A Pick

Thanks Chris - like I said - I am not a Tribologist, that is my Brother Scott so I will ask him to put his 2 cents up.

Paul
Paul Barrow

TRIBOLOGIST??? Couldn't help but look it it up. For those of you, who like myself didn't have a clue either. Here is the definition. "The science of Mechanisms of friction, lubrication and wear of interacting surfaces that are in relative motion" WOW! I'm impressed. You never know what you might learn on the Y Type site. Thank You Paul
Terry Y28669
T J Ciantar

Now, I don't want to open a can of worms, so I'll just mention my preferences and observations concerning oils suitable for old engines. Non-detergent oil must never be used! Always use a HD oil, which could stand for 'High Detergent', or 'Heavy Duty', and which contains an additve package.
Motor Oils, or more correctly Engine Oils, since motors are electric, are made to standards decreed by auto manufacturer's and governments. The current stuff has SN on the label. The previous standard was SM, and that had a little more ZDDP in it than the SN
has. If you are worried about losing your camshaft and cam followers while using SN oil, just drop a jiggerfull of STP into the fresh oil-it is mostly ZDDP. Even better, drop a tablespoon full of Moly
gear oil additive into the oil. All new engines have Moly coated components, and they last for hundreds of thousands of miles! Works great in gearboxes, too, but you need 5-10% by volume in there.
Years ago, folks used SAE 20W-HD in Winter, and changed to SAE 30HD for Summer. You can still buy straight weight, HD oils and they carry the SJ standard, which has loads of ZDDP. People mostly use Multi-Viscocity oils nowadays. These are made by adding lots of additives such as pour point depressants and viscocity improvers, so that the stuff flows like a low viscocity oil when it is cold, yet protects like a higher viscity oil when it gets hot. Fuel economy is impoved with these.
But, after the additive package is diminished and diluted, you end up with dirty SAE 20. An ideal Multi-Vis. oils would be a 3-stage, like 10W-30, or 20W-40.
In order to get a wider range like 20W-50, or 20W-60, even more addives need to be added. More additive=less oil. A good oil needa little additive.
Some oils are made from poor stock and loaded with additives. Many race cars advertise such oils on their bodies, but it would not be allowed in their engines. Never use 'Racing Oil' in a street car, used for normal driving.
Viscocity, or the 'thickness', or 'heaviness' of oil, is a measure of its flow characteristics. In the old days, if you started with a heavy bodied lubricant, you might end up with a protective film that was strong enough to protect moving parts from wear. Add in shock loading, and the lubricant needed to be heavier still. Old lubricants started out thick, and got thinner as the heat was poured on. Normally, you need about 2 Microns of protective film between the moving parts, if the clearance is correct. When oil is pressure fed to a bearing journal, most is squeezed out and the remainder behaves like a solid, as it does its job in the load zone. Modern oils are low viscocity with a high Viscocity Index. V.I. is a measure of an oils ability to maintain near constant viscocity despite changes in temperature. The clearance in a modern engine is very small, and the 0W-20, or 5W-20 oil is very low viscocity. It is not suitable for use in old engines! The clearance in old engines is greater and is further increased by wear, so a heavier-bodied oil is called for. Many people believe using straight SAE 40, or 50 would be better than using something lighter, and sometimes it does seem to work better. If you think lots of oil pressure is what you need, heavier oils will give it to you because viscocity is resistance to flow. For better protection, you want greater flow, not more pressure.
If there is alrady too much clearance/wear, the low viscocity oil may leak out without providing any protection, so you change to something heavier when you hear that rattling sound. It is probably too late, and you will throw a rod and destroy the block of your XPAG.
I could start another thread on the gasoline, or petrol we now have which contains alchohol, 10% by volume. It is terible stuff to leave in old fuel systems and carbys. It might also cause your valves to get sticky, so add a little Marvel Mystery oil to both your fuel tank and to your engine oil to prevent that. Always use MMO in air-cooled engines, as they are even more suseptible to valve sticking.
I hope you are not too confused-Good Night!
Scott
S.R. Barrow

Hi,

Looked up about Marvel Mystery Oil and came across this thread on Jaguar Forum.
http://www.jaguarforum.co.uk/viewtopic.php?f=16&t=30123&start=0

Interesting thread!

R E Knight

That's an interesting read from the Jaguar Forum.
Wintergreen oil, also known as Salicylic Acid Methyl Ester would make an intersting oil additive. Early synthetic oils, and some current ones are ester based.
A little ester synthetic oil added to another type of oil results in high detergent action.
Its too bad Marvel Mystery Oil isn't available in the U.K. Ask any old car owner here in the U.S.A. about it and you'll end up listening for an hour about its apparent virtues! MM Oilers were a common accessory items found on Packards, Buicks, Cadillacs and many other fine automobiles, installed by the dealerships back in the day.
I sold a Shorrock Supercharger to a gentleman in Scotland last year. The unit came with a MM Oiler and instructions which said to use only MMO therein.
We are fortunate to have such an effective, 'Snake Oil', readily availble to help keep our treasures running smoothly. Don't mock it if you haven't tried it!
Scott
S.R. Barrow

I will echo your comments there Scott - it is very good! I used it as an upper cylinder additive to "pop" a ring on an A Series engine that hadnt run in 40 years - worked a treat on that too!

Paul
Paul Barrow

Hi folks,

Here the link off the penrite brochure, there you can find the 20w60 oil.
That's the reason that I use 20W60 instead of 20w50.


Regards,
Klaas

http://www.angloparts.com/images_ap/newsletter/Penrite_brochure.pdf
K.S. Stuiver

I can see the appeal of formulated for most post war classics there Klaas, however the XPAG engine is a Pre-war engine.

However, as Scott points out, there is little difference between 20w/50 and 20w/60 and he does not consider that to be the source of the excessive pressure. There is something else going on. I would check again on the quantity of oil as registering on the dipstick when cold. If that is looking OK, run the engine briefly to make sure you are getting oil up to the upper gallery in the valves and that you are getting splash out there (messy but remove the valve cover and then be ready to shut the engine off if you do or do not get oil out. If you get oil out of the top, I would say run it for a while and rev it a little (with the cover back on) and see if it comes down a bit.

If it is over filled, drain the oil into a CLEAN catch container, and start over.

If you draw a blank, come back and tell us where you struck out - it may give clues to other issues.

Paul
Paul Barrow

ACTIV8 is an oil additive that was being heavily promoted at Beaulieu Autojumble this year. If you look at the video clip in the attached link it certainly seems to do 'what it says on the tin'.

http://www.bryanpurves.co.uk/activ8.html

Regards.
David Pelham

I have seen that old trick before. That demo was used in the US to promote a product called, "Power-Up". I don't know any customers who are still using it. Finest snake oil on the market. Think of this: do you have any lubrication applications like the one in the demo? Of course not.
Scott
S.R. Barrow

This thread was discussed between 26/09/2011 and 01/10/2011

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