Wednesday, 3 August 2011

Additives in oils?

Given the machinery we have may be quite old, we need to try and use an oil that mimicks what was available when that engine was new, just sticking some new synthetic oil in may not be the right thing to do at all?  Its all to do with more modern engines running at closer tolerances than say two decades ago, machines have become better and the oils have too.

I had an on going discussion with a friend who had his BMW/Hatz 50 diesel rebuilt by the importers and agents, it developed an oil pressure fault on the way to Brasil, he still had the engine running when he arrived in Trinidad but later changed it for a brand new Vetus diesel engine.

There was one issue we never cleared up,he used a product called Slick 50 in the engine.

His woes saw me pick up the phone and ask Shell Oils technical department what adding off the shelf additive  brands to their oils may do?

My call was diverted from Cape Town to Namibia and when the link was lost, I was phoned back, a most impressive service I may say.

The basics were explained, an older engine that had new bearings, sleeves, pistons, the whole show and at some cost, what does adding other than a straight oil such as Shell Rotella do to their oil?  The answer basically said that often while such additives may cure the complaint, they may cause another, so we left it there.

Read this as below,  which my source Dudley Dix sent me  Dudley has a common interest in classic cars, he has a Lotus Europa Mk2 and found this on the Europa web pages.

Disclaimer: This is posted with no warranty of any sort, read it yourself to basically understand how oils have seen manufacturers add to their own oils, then take the additives away.

You need in otherwords to make you own mind up on what oil to use?

The Imp original 875cc engine still runs on the same crank bearings and pistons that Rootes Car Co, Scotland fitted back in 1967, only the pistons rings have been changed.

My 1967 Hillman Imp Californian is using Shells 25W 60  oil for engines with higher mileage and seems to be working really well, good oil pressure and no oil used worth mentioning.

R McBride.

Some clue to the timing of GM's testing might be indicated by the revised

ZDDP levels between SE, SF and SG

1942 -- ZDDP introduced at 300ppm.
1955 -- API MS ZDDP at 800ppm.

In the 1970's there were problems with oxidation causing oil to thicken.
ZDDP is also an anti-oxidant, so ZDDP was increased to...

1971 API SD except GM, ZDDP at 1000ppm.
1971-80 -- API SE,  ZDDP unchanged at 1000ppm
Used by GM 1971-on, but cam/ tappet wear protection
proved inadequate and there was a rash of warranty claims.
1980-88 API SF,  ZDDP increased to 1500ppm

(compensating for an issue ?)

1989-93 API SG & 1993-96 API SH ZDDP 1200ppm.

(issue better ?)

Despite the ZDDP limits noted above, some oils of the day were available
with higher ZDDP levels, like Mobil 1 20W-50, which was 1600ppm ZDDP
(1600phos / 1700zinc). I can't explain the loopholes.
1997-01 API SJ & 2001-04 API SL ZDDP reduced 1000ppm

(back to 1971 level)

2004-now API SM

1) ZDDP 600ppm minimum level set
2) ZDDP reduced to 600-850ppm maximum for FIVE
select SAE 30 weight and lighter oils:.... (0W-20, 5W-20, 0W030, 5W-30 & 10W-30).
3) ZDDP 1200ppm maximum for all other non-selected
 grades. Manufacturers are "allowed" (not mandated)
to use 1200 ZDDP (1200 ppm phos. / 1300 ppm zinc).

The problem with SM is that increasing the ZDDP levels for the non-selected
grades is at the oil company's discretion. Some do, some don't, some go a
little, some go a lot. Many that do offer a higher ZDDP option select a
token viscosity grade instead of doing so across the range. For those SM
oils, the label tells you nothing about how much ZDDP is in the oil. It
can vary from 600ppm to 1200ppm and still be an SM oil. The inconsistency
creates a mine field for owners of vintage and motorsports flat tappet

When API SM was introduced, just about all mainline US oil company brands
and grades dropped to 800 ppm without an announcement. It wasn't until the
public outcry from vintage and motorsports groups that some oil companies
began to bump up ZDDP levels in select viscosity grades. The API SM spec
didn't change, it's still SM. But the way the oil companies chose to work
within the SM rating evolved.


Tim Engel


Back in 1972 when I was racing a Hillman Imp here at Cape Towns Killarney Race Track WPMC.
The engine was a 998cc block with a Rootes Competitions R20 camshaft,it would rev to 8000 rpm easy enough.

We had an issue with oil foaming in the crank case, at the time we put it down to excessive piston blow by, it was going to put us out of the race the next day?

1972 at the Killarney Circuit near Cape Town.

Photo by Eric Wells.

That night I thought my way through the engine, I realised that the engine was in a reasonably sound condition and I then suspected it was a change of oil brand that was the cause.

A more recent 998cc Imp engine that I built.

The next day we drained the sump and re filled with the oil brand we had always used (Duckhams Q 20w50) , the foaming stopped and we did the full race.

Proof even back then that all oils are not the same!


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