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MG MGB Technical - Engine oil

I know this has had some very thorough airings in the past but as I am contemplating a change of oil in the engine and gearbox. My 71 roadster has an overdrive so will clean out the filter at the same time. My question is what oils are being used and recommended by UK owners nowadays, the favourite of many in the past Duckhams 20/50 is not so easy to get now.
Any other suggestions apart from change of engine oil, filter and cleaning the overdrive filter would be appreciated. Thanks Trev
Trevor Harvey

I've tried several brands over the years paying attention to the ZDDP level, but they have gradually gone out of production or the levels reduced. They do still exist in the shape of Fuzz Townshend's Classic 20/50 but for me it's easier just to get Halford's Classic locally. If you have a rebuilt engine with new cam and followers then the higher ZDDP does seem to be beneficial.

OD filters can be tricky, one of mine came off OK and could be reused, the other delaminated and had to be replaced. There have been a number of complaints about replacement filters/gaskets leaking, it seems from the edges where the wire mesh of the filter material ends. Mine was fine. If the OD is working well then I leave everything else alone.
paulh4

I've been using Morris's Golden film 20W/50, but note that the ZDDP concentration isn't as high as some others so have been supplementing it with STP. I found a source that sell this relatively cheap (TFM). The last 5 litres I bought were £11 but have gone up to £18 now, even allowing for the £4 for the STP still cheaper than the alternatives. The specifications of some of the popular oils can be found here :-

https://www.classic-oils.net/Oils-by-Application-and-Type/Four-Stroke-Engine-Oils/Classic-20W50-Multigrades-Mineral-base

https://www.tfmsuperstore.co.uk/products/golden-film-sae20w-50-classic-oil-5-litre-2/
Paul Hollingworth

Valvoline VR-1 20-50 for me. Have used it for years. https://www.opieoils.co.uk/p-73741-valvoline-vr1-racing-20w-50-refined-mineral-engine-oil.aspx
Mike Howlett

Mike, Paul Hunt says on his Bee & Vee site (AKA Hammer & Spanner) that the most modern spec we should use in our engines is API-SJ. The valvoline oil you are recommending is API-SL which he says we definitely shouldn't use. I'd stay away from it unless you can be sure its got > 700 parts per million ZDDP. I'm tempted to go to good old Duckhams Q20/50 (1300 ppm ZDDP) next oil change, if I can find it at a reasonable price. Of course we don't know is how much ZDDP is enough.
Paul Hollingworth

I gave up updating that section four years ago as things were changing every year and I was having to search anew for the data. At that point I defaulted to using Halfords Classic by Comma. Comma Classic currently shows 800ppm for zinc and 700 for Phosphorus with 2200 for calcium. I have no idea what that ends up with when the zinc and phosporous are combined.

Is there a spec sheet somewhere that states how much ZDDP is in STP and how much it raises the concentration in 5L? STP has been around for as long as I can remember and was always bit of a boy-racer thing, the stickers being more popular than the products as I recall :o)
paulh4

Mike---asked the question from Valvoline a couple of years back--their reply--

-----" any stock flat tappet cam application, only requires around 800 ppm of Zinc for protection and approximately 730 ppm of Phosphorus, as Zinc itself will not serve the purpose. If you would like to use the highest Zinc content product we have, that would be our Valvoline VR1 Racing Oil, with 1300 ppm of Zinc and 1200 ppm of Phosphorus."

-about double of that in Comma's Halfords Classic at 800/700
William Revit

The information I remember so it might be incorrect (please tell me) is that Duckhams has 1300 ppm ZDDP and STP 1900 ppm. My understanding is ZDDP was reduced or possibly eliminated in newer specification of oil because catalysts don't like it.
Paul Hollingworth

My understanding on later formulations for 'modern' cars also.

STP will be 'diluted' when added to 5L. If Valvoline say "around 800 ppm of Zinc for protection and approximately 730 ppm of Phosphorus" is enough I have no problem using Halfords/Comma in a well-used engine. I WOULD use something like Fuzz Townshend's Heritage Classic at 1300ppm for a newly rebuilt engine, or one with new cam and followers at least.

I did get some VR1 from a Mini specialist many years ago for it's ZDDP content - once. It came in a black plastic cube-like container which reminded me of reclaimed oil. It was also only about a gallon despite being labelled 5L.
paulh4

The addition of the STP should increase the concentration of ZDDP by 200 ish ppm when diluted with the rest of the oil.
Paul Hollingworth

Trevor,
It's very difficult to put the advice about the benefit of ZDDP to the test unless it is by comparison of a significant number of identical engines having been operated the same way over a lengthy period. I suspect that advice about the concentration of ZDDP comes in the same way that mother makes her cakes: To 8 ozs of fine flour, add x ozs butter, y ozs of this, 3 drops of that and a generous sprinkle of whatever's left in the tin from the..... at Christmas. I have in the past paid serious attention to ZDDP but suspect that engines used at high revs with oil changes at 10K miles will show more signs of wear than from vehicles driven at motorway speeds between oil changes at 3K miles irrespective of choice of oils on sale here in UK. If you accept that noise and wear are linked, you might put PTFE to the test when you would detect that our pushrod engines run noticeably quieter after the engine has been run long enough for all the surfaces to be coated. The following link will tell you what you need to know. https://www.faher.co.uk/anti-friction-hd/
So sorry if this upsets accepted wisdom


Roger Walker

Roger
Funny you should bring this up
Back in the early 80's (yep, last century) we were approached by an engine additives company(name withheld) to try one of their friction reducing brews
at the time we were removing the engine for rebuilding every 4 weeks which they knew and they were keen to see inside when it was pulled for rebuild--We were a bit keen as well because the engine oil was getting fairly diluted/frothy with methanol from cold till it warmed up----Well, surprise surprise when it came apart, everything was white, even the crankshaft journals, camshaft, bearing faces and even the inside of the crankcase. you could clearly see that the bearing surfaces were not coming in contact with the shaft at all and the camshaft(roller) was completely covered white----it was doing what they said it would.
We didn't continue with it though only because it was a pain to clean up for inspecting/cracktesting but it appeared to be doing what it was supposed to do

willy
William Revit

My understanding is that the ZDDP is to prevent wear between cam and follower. (high force sliding contact)
The contact stress is generally highest on the nose of the cam at full lift. The contact force is worst at low speed because there is no inertia relief. This ties up with wear usually occurring in the middle of the follower.
There is a point around the transition between the flank (large radius bit) and the nose (small radius bit) where the eccentricity (distance from the centre of the follower to the point of contact) is high. At this point the entrainment velocity tends to zero meaning that there is no theoretical oil film. However this happens early in the lift of the cam so the contact force is low. Personally I've never seen follower wear towards the edge.
The B series cam is a 3 harmonic Multi Sine Wave design by a chap called Jack Bishop.
Paul Hollingworth

Willy, that's interesting. I expect that's the time the Navy got hold of it and created a waterproof long-lasting coating for its submarine torpedoes. That has been a great success which moved into the kitchen for non-stick pans. I think it's called Teflon there. Anyway a spanish outfit has developed it in an oil suspension which does the job without the colouring. The only trouble taking an engine to bits where it has been applied - it's so slippery. That can be a problem too ! (couldn't hold onto the rocker arm which left its mark on the wing).
Roger
Roger Walker

I have been using Valvoline VR1 and STP oil treatment. I recently opened the engine on the 1971 midget and the cam and lifters are perfect after 50K miles. The time before, the cam and lifters were deeply scored so this combination is working.

I have used STP since the car was new. It seems like a hold over from a different era but the original Midget engine lasted 171K miles with minimal wear before the the first rebuild.

I use the same oil + STP combination in the 1970 MGB.
Glenn Mallory

Roger- Yeah, in hindsight should have kept going with the plans they had for the stuff then we'd all be millionaires instead of just them.
On the teflon subject, i have a friend here that owns a freight ship that runs between here and the mainland. He had it built in (I think) Finland and had the whole bottom of it below the waterline coated in teflon for fuel economy purposes--It's worked out really well and stays as clean as a whistle----It was the first time they'd done it there (bit more common here, he'd had his old ship coated years ago)and there were a few toothing issues but he got the guys here to fix it up and the combination of that and running the thing on gas, it's been really worth the effort for him-
willy
William Revit

Willy - that is a logical follow-on for Teflon - Barnacles really slow you down and need to be regularly removed - with wooden hulls the answer was a copper sheath - huge cost but not so much by comparison with regular docking and re-painting. I wonder if our Navies have got round to using it yet.
Glen -whatever works. I haven't seen valvoline here.
It's difficult to believe that some of the oil producers have not included PTFE in their additives - can only be a matter of cost. I have heard that it accounts for the high cost of Mobil 1 here
Roger

Roger Walker

Roger, you are unlikely to see Valvoline in shops, but it is freely available mail order from several suppliers. Here's one
https://www.opieoils.co.uk/p-73741-valvoline-vr1-racing-20w-50-refined-mineral-engine-oil.aspx
Mike Howlett

Mike - I stand corrected - If I didn't already have the PTFE experience, I would go with Glenn's advice. This thread has useful advice for everyone
IMHO
Roger
Roger Walker

John Twist recommends the Valvoline Racing oil that Glenn uses. I have been using Castrol 20W-50 oil using a product called "Cam Shield" as a supplement, but will switch to the Valvoline on the next oil change.

As to STP, many claims have been made about it over the years, including a claim by the Consumer's Union that it was merely a "viscosity enhancer" (made the oil about one grade thicker than the base oil it was used with). I have never seen any claim that STP has ever been connected with any damage to any engine. I would use the version with added ZDDP, when doing an oil change, if I ran out of Cam Shield (which only requires about one or two ounces with each oil change and, thus, is less expensive than the STP).

Les
Les Bengtson

Les-
You can always recognize upon disassembly of an engine if STP® additive has been employed in it. All of its internal surfaces will be coated with a sticky, gray, slimy sludge. It will be gray because it retains metal particles that result from wear, rather than allowing the detergent additives that are in the oil to wash it away.
Stephen Strange

This thread was discussed between 17/03/2023 and 05/04/2023

MG MGB Technical index

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