semi synthetic or synthetic in a high miler

[philepo]

My last oil change used Shell Helix semi (its had Castrol magnatec all its life from the service book) and its has been fine. Car is c180 petrol and done 120K but engine in v good order - does not use oil.

Was wondering if I should carry on with the same semi oil change or use fully synth.

But will this make the car burn oil?

 

[C230kompressor]

if the book says use semi then i would stick with semi!

 

[welland99]

I researched oil thoroughly last month before deciding what to buy for mine. I began looking for oil which met the MB spec 229.1. I imagined that this would be a high specification which could only be met with fully synthetic, since several websites recommended only fully synth. oil when i entered in my reg no.

However, my research found lots of oils which meet this spec, including some semis and some enhanced mineral oils.

I decided on a fully synthetic oil from Comma (can't remember which one off hand). I got a deal on 4 bottles which worked out about the same price as 2 bottles of semi. :bannana:

 

[Roger Jones]

"Was wondering if I should carry on with the same semi oil change or use fully synth."

Carry on with the same oil. Changing to synth won't make the car burn oil, but it's more expensive and unlikely to impart any real benefits. If it ain't broke, don't fix it.

 

[nickcc101]

Handbook for my 2001 111 engined W203 states use fully synthetic.

 

[grober]

If it ain't broke don't fix it! Using a fully synthetic oil won't make the engine burn oil but it may leak a bit more. e.g. thro the front crankshaft seal. A fully synthetic will probably have a wider viscosity range 5w40 / 0w30 rather than the 10w40 semi-synthetic which means it will be easier to turn over on very cold mornings and "in theory" you could extend your oil change intervals slightly but this would probably be offset by the increased cost of the fully synthetic oil. What I would recommend however is changing your brand of oil from Castrol Magnatec to either Fuchs Titan XTR 10W40 Fuchs TITAN XTR 10W/40 High Performance Semi-Synthetic Engine Oil or Millers XSS 10W40 Millers Oils Both meet MB 229.1 and in my experience stay in grade longer than the Castrol product due to their higher synthetic composition.

ps. Shell HELIX PLUS 10W40 is a semisynthetic and is prefectly OK just not my first choice. http://www.shell.co.uk/home/content..._helix_tpkg/product_range_classic/helix_plus/

 

[C240Sport97]

I use Mobil 1 (cheap from Costco) for my 250k mile E230 210 estate.

Engine does not leak, and runs fine.

 

[philepo]

Thanks

Thanks for that. The engine does not use oil but does weep oil out of the front camshaft seal (i think its that anyway) so I won't go for fully syth. Prob stick with Shell or the ones recommended above.

 

[philepo]

thought about oil viscosity

just had a thought about this: if the fully synth is say 0w40 then when it is warmed up it will have the same viscosity as a 10w40 so surely the engine won't use more oil just becasue its fully synth??? Or will it.

 

[welland99]

just had a thought about this: if the fully synth is say 0w40 then when it is warmed up it will have the same viscosity as a 10w40 so surely the engine won't use more oil just becasue its fully synth??? Or will it.

Good point.

 

[welland99]

Both meet MB 229.1 and in my experience stay in grade longer than the Castrol product due to their higher synthetic composition.

I would have thought that any oil meeting 229.1 would stay in grade long enough for the service interval specified for the car.

Do you not think that is the case?

 

[grober]

I would have thought that any oil meeting 229.1 would stay in grade long enough for the service interval specified for the car.

Do you not think that is the case?

I would agree that CASTROL Magnatec 10W40 oil will meet Mercedes Benz 229.1 when its new. However like all oils including the ones I mentioned they will inevitably fail as they get contaminated/degrade with heat. This will take place at different rates for different oils. Eventually they will no longer meet the specification. As you point out one has to assume that oil longevity forms part of the MB 229.1 specification and would presumably influence the service interval recommended. However this does not mean that all engine oils will have the same "retained" lubrication quality at the service interval--some will be better than others. One might just be adequate whereas another may still be well within spec. If prices are similar I would would go with the 10w40 semisynthetic with the best "retained" quality hence my rather empirical recommendation based on my experience. There is a rather interesting discussion on the merits of the Castrol MAGNATEC brand here. Castrol magnatec: Motoring Technical matters forum