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Old 29-07-2009, 06:19 PM   #1
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10W-40 full synth oil - Smart car

Hi,

Due to increased oil consumption I'm looking to change the oil in the wife's 2003 Smart car. From a Google search I'm led to believe that a 10W-40 fully synth may help, currently I use 5W-40 fully synth. Though I appreciate that an engine rebuild may be on the cards before too long.

Halfords sell, Mobil Super S 10W-40 semi synth

GSF sell, Titan Diesel 10W-40 fully synth

1. Since I change the oil every 5k is semi synth OK?
2. Are oils branded for diesels OK for petrols?

Thanks for any advice.
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Old 30-07-2009, 07:17 AM   #2
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1, i cant see a prob with semi.

2, plenty of diesel mechs run their petrol cars on the companies diesel oils

Plenty of hgv fitters i know have never bought engine oil in their lives

If the engine is worn and its using oil you may as well go for the semi, it will use more oil on syn than on semi with the same viscosity.

To many people are hung up on syn oil.

Do some googling on what the base stocks of syn oils are etc

How many miles has it done ? just curious as bloke at work has a roadster and reckons the engines are only good for 40k ish.

Simple example, trucks i work on up to 56 plate all ran mineral oil 10/40, even the million milers hardly use any oil, 07 plate onwards all run 10/40 full syn all singing and dancing oil and they drink it, anywhere between 3 and 12 litres every 6 weeks.



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Old 30-07-2009, 07:59 AM   #3
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Quote:
Originally Posted by lynall View Post
1
How many miles has it done ? just curious as bloke at work has a roadster and reckons the engines are only good for 40k ish.

Simple example, trucks i work on up to 56 plate all ran mineral oil 10/40, even the million milers hardly use any oil, 07 plate onwards all run 10/40 full syn all singing and dancing oil and they drink it, anywhere between 3 and 12 litres every 6 weeks.
Thanks for all that info Lynall.

The car (700cc turbo) has done 47k miles and burns roughly 0.5L in 1000 miles. It may be a little less, as I've not been measuring up to now.

Are semi synths OK for turbo bearings? I presume the trucks you work on are also turbo charged?
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Old 30-07-2009, 08:30 AM   #4
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Semi synths are fine for turbo bearings
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Old 30-07-2009, 08:44 AM   #5
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Whilst I think of it......I've read some of:

Car Bibles : The Engine Oil Bible
and
Car maintenance bibles: Oil Viscosity.

but it's still not clear in my mind whether changing from 5W-40 to 10W-40 will mean that the oil will be more viscous on a cold engine start up and short journy town driving. Does anyone know?
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Old 30-07-2009, 09:44 AM   #6
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I would use a grade that meets the MB rating recommended in the manual. Good synthetics should resist thermal stress ( in turbo bearings and oil passageways for example ) better than a semisynthetic. The problem with semi synthetics is the proportion of "synthetic " component there is--this varies widely in terms of composition and percentage component from make to make . Diesel oil has a slightly higher percentage of chemical "mopper ups" like detergents etc to cope with a greater proportion of combustion products escaping past the piston rings in diesels,although in modern oils I would guess the difference would be small. There will be a slight difference using a 10w40 on starting a cold engine which will be more noticeable in the cold winter months. You will experience the loss of several mpg using a higher viscosity range oil- difficult to predict exactly how much. I think my approach would be to stick with the MB recommended grade of oil and devote a bit of research to finding the cheapest source for an oil that meets the spec.

big discussion here.
http://www.smartcarofamerica.com/for...40-0w40-24278/
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Old 30-07-2009, 10:04 AM   #7
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Thanks Grober.

The more time I spend reading about it the more I am inclined to do nothing.

AFAIK burning oil in itself is not bad, other than it's an indication of engine wear, which a higher viscosity oil wont cure. The car also recently passed its MoT and therefore the emissions are OK too.

So I think the safest option will be to keep using the 5W-40 oil that meets the MB spec and regularly check and top up the oil as required. The oil only costs 16 for 4L, so the cost is trivial.

I remember my Audi A2 diesel used longlife oil at 10/L and that drank oil too.....so maybe I'm worrying over nothing really.
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Old 30-07-2009, 06:53 PM   #8
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Can't use semi. The car has a turbo in it. And the semi will be burned in it, leaving traces, which will end up with broken engine.
This is the types of oil, you can use in your smart: Evilution - Smart Car Encyclopaedia

btw, how much is it consuming on 1000 miles? If less then a litre, it's still fine, if more - engine overhaul (rebuilt) is coming.
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Old 30-07-2009, 07:01 PM   #9
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If you are happy to try a Semi-synth whilst it is burning oil, you could try GTX High Mileage, it's a semi but it also has seal rejuvinators and burn off inhibitors in so will possibly help the rings 'bounce' back a little and will help prevent hot spots on the valves when the oil does pass the piston rings. We use it in Smarts quite often at work and if used as a short term measure we haven't seen any problems.

Kate
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Old 30-07-2009, 07:16 PM   #10
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Originally Posted by lil.smartie View Post
If you are happy to try a Semi-synth whilst it is burning oil, you could try GTX High Mileage, it's a semi but it also has seal rejuvinators and burn off inhibitors in so will possibly help the rings 'bounce' back a little and will help prevent hot spots on the valves when the oil does pass the piston rings. We use it in Smarts quite often at work and if used as a short term measure we haven't seen any problems.

Kate
Thanks for the info Kate.

Is the GTX High Mileage a 15W/40?

When you say 'short term measure' do you mean as part of frequent service intervals (~5k) or for use before the inevitable engine rebuild?

I ask as I'm interested to know which oil will best preserve the current engine condition. Does oil burning damage the engine and therefore it's less harmfull to use a semi synth that does not pass the piston rings?
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Old 30-07-2009, 07:30 PM   #11
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IIRC yes 15w40. We use it after a rebuild for the first few 1000 miles to help everything bed in then change back to fully synth with an oil & filter change. We also have used it when oil consumption starts to increase and on some cars it has stopped the consumption, some customers have then gone back to fully synth, others have stuck with the high mileage. If a semi has used all the time (for years!) we have seen 'sludge' in the engine once it gives in and is pulled apart for a rebuild, although I can't remember seeing one that's been in after using high mileage short term & fully synth the rest of the time so not 100% what the situation is when that combo is used.

The high mileage will still pass the rings if they are 'stuck' but it will help stop any further damage being done as when the fully synth sits on the valves it burns, creates hot spots & can burn out chunks of valve whereas the high mileage resists the burning.

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Old 30-07-2009, 07:40 PM   #12
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wemorgan, if it's burning 0.5 litre on a 1000 miles, I wouldn't bothered yet. Just top-up with oil, and keep an eye on it.


Offtop:
Kate, hello there One more person from the other forums
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Old 13-08-2009, 08:32 AM   #13
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Just a quick update to this thread.

After 500 miles of motorway and hilly (Cumbrian & N.Wales) driving the Smart burnt another 0.5L of oil.

But then on the 200 mile motorway journey home it didn't burn any.

So I'm going to check the spark plugs this w/e. They're only 1yr/6k miles old. So if there's any sign of oil damage I'll replace the plugs and change the oil to a 10W/40 and see how that goes. If there's no sign of damage I'll change the plugs anyway but continue to use the 5W-40 oil.

ps. During the 500 mile journey I drove over 1 nail (repaired) and noticed a gash in the side wall of another tyre (replaced). 70 later all fixed. What the Smart saves me in petrol it costs me in oil and tyres!
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Old 19-08-2009, 07:34 PM   #14
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Exclamation Oh dear!

I've change the spark plugs and here are the old ones. For those that don't know the Smart car has 3 cylinders with 2 plugs per cylinder. These plugs are roughly 1 year & 6k miles old.

Is it possible that the idiot (me) didn't tighten them up properly? (they seemed hard enough to undo, so I think unlikely)

I've been told that Smart bottom plugs usually soot up more than the top. But all plugs look like oil is burning in the cylinder.

I'll change the oil tomorrow for something thicker (10W40 or 15W40) and see how it goes. But I'm not expecting a positive outcome

Any advice welcome.

Top plugs:


Bottom plugs:
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Old 19-08-2009, 07:51 PM   #15
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Remember a 10w40 or 15w40 will only really be thicker when cold, when hot they will all be "40" - so most of the time you won't be using a "thicker" oil.
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