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MG MGB Technical - Collector's Choice Motor Oil

Always used Castrol GTX 20w50 until I heard they stopped the ZDDP. Been using ZR-1 racing oil it
seems ok. Anybody try Collectors Choice by Hicks Oil?
Raymond Puder

Check the API ratings. SM has very low ZDDP and should be avoided, it is known to cause problems. Ideally SJ is the latest rating you should use - if you can get it. Some 20W50 brands are still SJ as modern cars that need the later specifications don't use them. Can't speak for GTX 20W50 as we can't get it in the UK, only 15W/40, and that is SL, but 20W50 is said to contain half the ZDDP it used to. It would be interesting to know what that spec is - SL or SM. Valvoline VR1 20W50 in the UK is SL, but claims to have 75% more ZDDP than SM, but they don't say how that compares with SJ. Royal Purple claims to have 1500-1600 ppm of ZDDP and states "we could take all the ZDDP out of our oils and still have 4-times the wear resistance of VR1".

You might be better off with a Diesel oil, these generally have more ZDDP than petrol oils as the little ends need it with Diesel combustion characteristics. If it specifies the SJ rating for petrol engines as well as C-something ratings for Diesel that will be the best option.
Paul Hunt

Can't find the API ratings on the bottle. Moss Motors in California is selling it for $6.00 a quart. I found it in St.Louis at Fastlane Custom Autos for $4.50, not much more than VR1.
Raymond Puder


Here in Canada you buy ZDDP additive or you rely on motorcycle oil like Castrol 20w50 with ZDDP in it for one or two more years.

Jean Guy Catford

Zinc additive, ZDDP, is critical, as I understand it, for engines just after rebuild. Day to day, and for most applications, an oil like Castrol 20W-50 will do just fine.

Is my understanding correct?
John Z

I had the same dilemma and it prompted me to call each of the below oil manufactures. They were all aware of the ZDDP problem with older engines and each had a recommended oil with sufficient levels of ZDDP to avoid the wear problem. They each gave me the percentage of ZDDP but I did not include the info in my notes. I do remember that Pennzoil racing oil had the highest level with the others being about the same. I choose Valvoline racing oil 20W50 because it is available in my area whereas Pennzoil is not. Below is the recommendations that were provided.

Recommended Motor Oils for The MG

Castrol: Syntec 20W50
Valvoline: Racing oil, VR-1, 20W50
Shell: Rotella HD diesel/automotive, 15W40
Pennzoil Racing Oil, 20W50
Mobile: Mobile 1, 15W50
Delvac Diesel, 15W40, or 5W40
Frank Grimaldi


That is how I read the information. Critical for startup and breakin. I used the GM ZDDP additive and the red STP (used to have good ZDDP but not sure about current levels).

First oil change I went to VR1.20/50 Can't see a reason not to stay with it.

I found that my local Walmart occasionally stocks a motor oil
(I can't remember the brand name) for pre-catalytic cars
(SJ rated).

They often run out of the stuff and are spotty about keeping
it in stock.
Daniel Wong

API SJ and earlier is best, not SL, and definitely not SM. Diesel-rated oils usually contain more as their little ends need more protection. If they quote the same API SJ petrol rating or lower as well as the C* diesel rating they should be fine.

Valvoline claims VR1 (SL) contains 75% more ZDDP than SM, but doesn't say what that level is or how it compares with other oils. Unless VR1 contains the required low level of ZDDP it couldn't be classed as an SL anyway.

I've seen a claim purporting to be from Royal Purple to the effect "RP XPR 10W40 has over 1500-1600 ppm of ZDDP and, get this, "we could take all of the ZDDP out of our engine oils and still have 4 times the wear resistance of even the VR-1 oil due to our Synerlec additive technology".

"Lies, damned lies, and oil claims", to paraphrase, leaving the consumer none the wiser.
Paul Hunt

i have great difficulty getting a decent 20/50 oil. the last i used was halfords classic. its got on the tin api se cc. what does this mean and is it any good. its the same colour and smell as duckhams Q 20/50 classic oil.
Bob Taylor


API SE is good. You can also get a Comma Classic oil which is the same (probably Comma make it for Halfords or Duckhams make it for both!)

Chris at Octarine Services

I have just received some information from Comma, concerning the zinc and phosphorus content in their Sonic 20w50 and Classic 20w50 oils. Sonic API SL has 0.15% of both, Classic API SE has 0.07% zinc and 0.06% phosphorous.

I would have thought it was the other way round, but this is what their data sheets say.

I have used Sonic 20w50 for the last six years, seems to work well for me.



API SE *should* mean it contains the higher levels of ZDDP, or other means of getting the required protection. The thing that bothered me with Halfords Classic is the unsealed tins, anyone could put anything in there anytime.

Zinc isn't the same as ZDDP, which is zinc dithiophosphate. Could mean the same thing of course, unless they also have a figure for ZDDP. This *safety* data sheet quotes less than 1% ZDDP, which could mean none at all.
Paul Hunt

"Zinc isn't the same as ZDDP, which is zinc dithiophosphate. Could mean the same thing of course, unless they also have a figure for ZDDP."

Interesting point, Paul. Can anyone on the BBS explain this?

The safety data sheet for Sonic 20w50 says ZINC ALKYL DITHIOPHOSPHATE 1-10%. That seems to confirm a higher level than in the Classic 20w50.

I think I will continue to use the Sonic rather than the Classic.


Tore - when someone says 'zinc' they may well mean 'ZDDP'. If an oil contains some other formulation based on zinc but not ZDDP, then it may well be irrelevant in terms of wear on things like cam and tappets/cam followers, which is what ZDDP is designed to protect.

With 'recommended' oils for the MGB you must bear in mind that formulations can and do change over the years, so what may have been 'recommended' five years ago may now not be appropriate.
Paul Hunt

When I was looking for oil last weekend, I looked at a bottle of Rotella Diesel oil, which showed CH-4/SM on the label. I decided against it as the SM makes me think that there is likely not much or any ZDDP in it.
I found Castrol 4-stroke 20W50 motorcycle oil, with API SJ on the label, and grabbed 4 litres of that. Maybe I should have taken more and stocked up in case they discontinue that, it was about $4.50CDN per litre. I like the 20W50 as the leaks seem a bit slower than with the 15W40 diesel oil I had been using - as hard as I tried to prevent any leakiness from my engine at the last rebuild, it still leaks from the front plate or timing cover area, hard to tell which.
Erick Vesterback

I always hear about engines leaking. Why not run a bead of silicone etc? It always works for me.

I've been using the Castrol 4T 20w50 for over a year now. It is designed for motorcycle engines under high stress. The oil pressure seems to hold 10lbs. higher than with 20w50 GTX. The newer diesel oils now how lower levels of ZDDP to meet emission regulations. RAY

Indeed, which is why anything with 'SM' on it should be avoided like the plague, SL ditto. SM in particular is low in these sorts of things partly for ecological reasons, and partly because the reduce the life of exhaust cats. Modern engines are designed to tolerate it.
Paul Hunt

Honda motorcylce oil is still available with the SJ rating, it comes in 10-40 and 20-50. Any Honda motorcylce dealer should have it in stock, it comes in quart as well as gallon jugs. It will probably cost around 6 dollars a quart. My MG hasn't run since before this oil problem started so I don't use any oil in it at the moment. I use Chevron Delo 400 15-40 in my Chevy Van that has a 350 V8 because it has more zinc/ZDDP and we all know pushrod engines like that stuff. If you want to run diesel oil look for the older CI or non "low emmission" formula, you can still find the older stuff if you look hard enough.

Jared Snider

I contacted STP because one of their products was recommended when our club discussed this modern oil problem. There is a 15oz container of the STP 4 cylinder anti-wear supplement (my words) for sale in a red plastic container with a red top. I searched high and low at all the area car supply stores before some one gave me a clue that it might be found with all the other weird things one can find in the local grocery store. Sure enough, I found one store and stocked up from 2 others carrying this product along with car perfumes, hula dolls and key chains.

A STP rep sent me the following email: “Both the blue and red bottle contain ZDDP, this is why many classic car owners with flat tappet cams use the product. You will get the same protection from the blue bottle as you will the red. The amount of ZDDP in our products is proprietary.”

I’m still confused why this product is not available at autozone, carquest, NAPA, orielly’s etc.

Hope this is helpful
Danny Jacob

I have used Texaco Haloline in MGs since the early 60's. My current B runs Havoline 20W-50 which has a rating of SH,SJ,SL and it is approaching 130000 miles. I have always added STP at oil change time.
Jimmy Chew

Hell you lot have opened a can of worms!!
Am I right in assuming that the SJ, SL, SM etc., are "time" related? That is, SF is an earlier spec. I've just looked at my container of Morris Oils Magnol 20w-50, which I've used for years. It says it is suitable for use in petrol and naturally aspirated diesel engines needing API SF/CC lubricants.
WHere does this fall in the ZDDP debate?

S* ratings are indeed time related, see

SF is suitable for 1988 and older engines, SE is suitable for all MGBs purely by age, but taking technology into account you could probably go as far back as SB! SJ is probably the most modern we should use, but earlier is better. Castrol do Classic XL 20W/50 in API SE, available in the UK at least. They do five gallon drums, but I have seen a recommendation that it shouldn't be kept longer than five years, and it must be frost free.

As for "The amount of ZDDP in our products is proprietary." then it's meaningless, and they could change (i.we. reduce) the levels at any time, or change the formulation in any other way, and not tell you.
Paul Hunt

Well in that case good old Morris oils of Shrewsbury seem to have the answer. I've always found them very helpful on the phone, they seem a good company, with the right attitude and a sincere faith in their products! Give them a call. 01743 232200

I notice that some "Classic" oils are API SE, but never really understood why it should be an advantage for our engines to use 1972 oil technology. Up to the latest SM, and some SL oils, where too low zinc and phosphorous content is a problem, all the earlier generations SF, SG, SH and SJ have been improvements on the SE. Improvements in deposit control, oxidation, wear, rust and general corrosion. And surely our engines too benefit from that?

I did advertising for Castrol in the early nineties "SG" era, and as some of you may remember black sludge was then a big problem, possibly caused by reduced fuel quality. Improvements in oil cured that. I also worked with Scania trucks in the eighties and nineties. They said that the main reason why the average engine life increased by four from the sixties to the nineties was better oil.

I realise that improved detergents can be a danger to an engine that has run for decades without being touched. I know one MGB engine that was damaged because it was full of dirt that came loose when it was filled with modern synthetic. But when an engine has been overhauled, like I did with my MGB engine in 2005, I see no reason why it should not be kept as clean as possible?

I have run my engine on SJ oil after the overhaul, and the visible parts in the valve gear looks as clean as when I put it in. I wonder if many of the "Classic" SE oils are just pure nostalgia at a high price, just like the tin cans they are often sold in?

I also notice that Miller Classic 20x50 are SJ (1997), and Penrite Classic 20w50 is SG (1989). I believe both are regarded as quality oils?


This thread was discussed between 03/04/2009 and 05/05/2009

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