Oil Specs?

mercedes use their own specs for oil, at a car shop you would expect to pay about 25 for 5l. of a make such as Granville that meets the merc specs. or double that for a top brand.

The short answer is "yes". The API and ACEA specs are quite clearly defined.

There are at least 3 different specs of modern fully synth oils.

It's not clear what the different additive packages are. Some may react badly with other oils and additive packages. If it's in warranty you have to use the stuff they tell to as if you suffer engine damage they will do an analysis for whatever they consider to the be the tell tale marker in the additives.

Gearbox oil is even more critical to get right. G5 eats brass and bronze in the synchromesh rendering a gearbox that requires G4 scrap quite quickly. But many oil makers now produce a G4/G5 grade that can be safely used in G4 gearboxes.

Likewise old R12 filled air con can use a grade of oil that gels with the oil used for newer and more common refrigerant hcf134a. But some old R12 systems have the new oil in them. While the latest refrigerant(s) require oil that is incompatible with the one used for hcf134a.

The manufacturers try quite hard to ensure that their additive packages are compatible, for given ratings. What you don't do is mix your PAO and PAG base oils.

Correct, it is the high sulphur, phosphorus, or chlorine extreme pressure additives that can kill your copper alloys.

Now I have visions of sacrificial offerings of blood being made during the ceremonial oil change.

Not unless the sump plug or filter is too tight ;-)

Hmm, but what isn't clear, at least to a non-specialist / expert, is what those spec translate to in real terms.

One, for example, seems to relate to 'anti splash' properties. While I doubt this means splashing around making a mess, why do Mercs need to specify it and Hondas don't? (A rhetorical question perhaps, it may be to specialist for here, I certainly don't know.) I just wonder if, for example, your 'average' non-specialist garage would just use 5-30W from a big drum, regardless.

That was my thoughts.

Given it is a once a year job and the Smart only uses 3.5L of the 5, chances are I'll get 3 services from 2 * 5L (allowing for the containers having a bit more than 5L), I'm not overly bother. I was more something I was musing over as the oil drained this morning.

On a different topic, I always check the spark plugs. While the car has only done about 17k miles from new and they looked perfect, I can't remember the last time I saw a 'worn' plug. I replaced the originals in the CRV with some 'super' plugs, not because they were worn, but because the super ones (supposedly) gave improved fuel economy (hmm...)

you can't see wear on a plug. just replace them with the right ones on a mileage schedule. Many nowadays are 40k miles, some are 100k

I'm intrigued.

I've noticed that, besides my own (admittedly amateur/home mechanic- and even that is a bit grand these days) observation that 'plugs don't wear' (note the quotes, following your input), the car service schedules I've had specify far longer replacement mileage / time for plugs, when compared to, say, my first car- a Mk2 Ford Escort. .

On cars of the Escort 'vintage', you could see signs of visible 'wear' (although not by contact!) of the electrodes. Regapping was commonly required etc.

For plugs that have a conventional gap, I struggle to recall the last time I even did anymore than check it. My CRV did have plugs with a conventional gap but, prior to replacing them with multi electrode plugs (which I'm sure you know you don't/can't change the gap on), I don't think I even adjusted them. Ditto my MX5, which I had from 1999 until last year, although I changed that to the multielectrode plugs perhaps 3 years ago. I did, of course, check the plugs, if only for peace of mind and to ensure they were the right colour (old habits) and didn't become stuck (I once worked on a friends car which had a stuck plug, I doubt the plugs had been removed in 10 years.)

I don't doubt what you say, your experience/knowledge is far greater than mine, but I am curious what the wear out process is of a modern plug in a modern car, assuming the electrodes appear not to have worn - ie the gap is right, and they clean up etc. I'd expect the normal colour on the cone insulator (electrode end) of course, and perhaps some staining of the white section near the cap- even that sometimes cleans off.

Modern plugs are a different breed to those of 50 years ago. And different again to those of pre ww2. Modern plugs also come pregapped.

If you can see an increase in the gap then the plugs have been in for much longer than the service schedule specifies.

Leaving plugs (or plug leads) in for too long nowadays can lead to a written off car! Think coil packs, leads and an ecu plus fitting.

Modern engines run very lean and clean, meaning weird plug nose colours are the norm. The old chart with the light brown plug nose is very out of date.

Cleaning plugs has been a no-no for at least fifty years too, the only acceptable method is to blast clean them.

Removing and refitting long life plugs can be a good idea on engines where they are prone to seizing in place, but that is not very common on modern English cars. Fiestas and KAs could be troublesome, but most of those have gone.

Interesting but it still doesn't explain what wears. I'm not disputing they do wear, I would just like to understand where/how.

As it happens, my plugs still tend to be the traditional light brown - even if it no longer means anything ;-) Speaking of colours, I inherited a Colour Tune. I've never used it, it came my way perhaps 25 years back- by which time I suspect it had been rendered obsolete, other than for older cars. I don't think it has ever been used.

with modern plugs the electrode material is tougher, so loss of material leading to an increase in gap is less noticeable.

electrical breakdown is more of a problem leading to tracking internally and externally and lack of spark problems

Fair enough, assuming it is age related.

As it happens, we tend not to do high mileages so I don't worry about 'squeezing miles' from plugs, oil, etc. I'd much rather be sure the car is in looked after. I just like to understand things.

Nearly all modern plugs are "fine wire" electrode. This is made from gold palladium, platinum or iridium. Gold palladium were 1st generation fine wire and used solely for racing (£10 a plug in the mid 80's). Platinum were introduced in late 80's for fuel injection with catalytic converters, the fine wire gives better anti foul and reliable ignition at idle. A misfire (not pre ignition) dumps raw fuel into the exhaust which will damage a cat. Iridium were introduced as a lower cost replacement for platinum. None of these will show signs of wear visible to the naked eye in 60K miles.

Some have "targets" made from the same material as the wire welded to the earth electrode. These are intended for wasted spark systems that have 1 coil firing 2 plugs (2 coils for a 4). One of the plugs fires in opposite direction to the other, earth to tip instead of tip to earth.

Old plugs c1970's have a wide tip on the electrode, the edges of which become quite rounded in about 6000 miles. The copper core plugs produced by NGK were far superior to all other makes as they had far wider heat range preventing fouling. A motorbike I had was running badly due to a worn plug, with a brand new Champion plug it wouldn't run at all.

I'd quite forgotten the various plugs we'd seen over the years- your summary was like a walk down memory lane. I remember fitting a Platinum Plug to a motorbike in 1979, I can't recall the price but I do remember it seemed like and arm and a leg.

Of course the other thing which we no longer need to worry about is 'points', either setting the gap or ensuring the timing is right- it 'just happens' (well, you know what I mean).

Remember my first Rover V8. Was a 69 3500, so not the first of them. And it suffered badly from plug fouling. Until a different plug was recommended by the factory. Some three years plus after the engine was introduced.

I change oil and filter four times a year on my Saab 9000, using the cheapest supermarket oil that I can find, as long as it's fully synth with modern spec. Last oil I used was labelled RAC and bought from BM shop.

Apparently, the spark plugs in this engine play part of the knock sensing; the system is designed around specific NGK plugs. It's well known among saabists that any other more advanced plug will just cause trouble. The plugs are also self-cleaning by some system. But I change the plugs at 24,000 no questions asked, but they always look fine.

I was wondering about this a few days ago. carparts4less have two different Triple QX 5w-30 synthetics: Triple QX Ford and Triple QX GM They are both API SL/CF, but one is ACEA A5/B5 and the other ACEA A3/B4

Googling found this explanation of the difference in those specs:

from

Once upon a time it used to be relatively simple. These days with all the focus on fuel consumption and emissions the manufacturers do a lot of "fine tuning", hence this supplier doing two variants for different manufacturers.

The good news is that for most things oil consumption is negligible, so you only have to worry about choice at service time.