I have a drum of engine oil labelled SG 10-30W. According to Castrol I
shouldn't use category SG in engines newer than 1993, I should only use
SL in the newest engines---but then they want me to buy more oil. Does
anyone know if I could use SG in current engines?
I've had the same dilemma quite recently and asked a mechanic friend to
explain it to me. The story is that newer engines are set-up not use as
much lead additives than older engines and that older types of engine oil
have high lead content. Because of this, the materials that make up the
rods and piston parts don't take to well to high lead content and can
actually rust more quickly.
Well that's how it was explained to me anyway.
That is truly bizarre. Nothing I've ever read about engine oil,
and no lecture I've ever sat through on the subject has ever
indicated that lead was ever used as an oil additive.
Can anyon else confirm this?
That's just BigWallop away with the fairies yet again
SG is fine. It won't last as long, and it's probably made from
recycled oil rather than fresh synthesis, but it's a perfectly good
The problem is that it doesn't meet emissions regs for California,
where type approval (not even the annual inspection) tests a few more
emissions than we usually do here. This is mainly due to unrefined
recycled crap, rather than the SG rating itself. As such, a blanket
ruling is simplest for the oil companies. 10-30W SG must be a few
years old though ? I've only seen it as 20-50W recently, sold for
oil-burners with no rings or valve guides.
In '97 I was looking for SJ rated oils and simply couldn't find them
anywhere. In the end I found one dealer in the whole city who knew
what I was talking about, knew that the S* rating system went beyond
SH and stocked some (Valvoline). Now you can hardly buy anything of
lower grade than SI, unless you go to Wayne's Escort Emporium in
I wouldn't use it in a turbo though, because of the coking problems.
I don't know how old it is. It came with the house! I have various drums
and containers of oil, the SG, some chainsaw oil, some diesel engine
oil. The latter is the only one I know I can use, in the diesel
generators. The chainsaw oil can be used on bicycle chains though
opinion is divided on its usefulness. The previous occupants had older
cars/motorbikes and so they may have used the SG on that though it is in
the generator shed rather than the garage.
Now, the one thing I have learnt is that category SI doesn't exist, they
(the SAE) went straight from SH to SJ to avoid any confusion with the SI
of SI units.
First I've heard of it too. Also, to the best of my knowledge there's been
no change in piston or bearing material of any consequence.
However, I'd stick to the recommended oil. If it's an old car from when
the oil was current, then perhaps ok. But on a newer car with extended oil
changes it's really not worth the risk - oil is a tiny cost in motoring.
I remember someone posting a URL which explained all the various
classifications of oil. These are not defined by the maker, but by
independent bodies and sometimes also individual car makers. I've got this
one bookmarked under oil, which may explain some things.
*Elephants are the only mammals that can't jump *
Dave Plowman email@example.com London SW 12
I have never heard of this. It is quite possible that when leaded
fuels were used, some lead got carried into the oil via blowby.
Perhaps there is some confusion with zinc dialkyldithiophosphate
which is being cut back because it shortens the life of the
catalytic converter. In theory of course, engine oil won't get
into the cat, but there is a degree of two-way transfer between
the hot side and the oily side of an engine. The bigger oil
manufacturers do a service for fleet owners where they analyse
for metals to pinpoint imminent problems with the engine.
If you have nothing to say, or rather, something extremely stupid
and obvious, say it, but in a 'plonking' tone of voice - i.e.
roundly, but hollowly and dogmatically. - Stephen Potter
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