Mixing Oils

d215yq

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Time for an oil and filter change...I measure I have 2.3 litres left from last March's oil. So as capacity is 7.1 litres I can only buy one 5L pack this year :). Will get to the same MB spec again but assume I can mix totally different brands of oils in this way?

I notice that in winter months the car uses hardly any oil (less than a quarter of a litre for over 5000 miles), however in summer (35 degrees plus ambient temp) after long motorway trips/ particularly including long windy mountain climbs the car can use up to half a litre every 3,000 miles. Should I increase viscosity (currently use 10W40) and if so can I mix viscocity e.g, 5L of 10W50 and 2L of old 10W40?

I don't really mind topping it up, although the rather bright oil warning light comes on at just under half, and usually decides to do that at the start of a long night drive thus being exceptionally annoying so if it uses less oil then all the better :)... I remember starting the long night drive through France once where there's no street lights and 5 miles in the oil light flickers on. Was so bright/annoying I stopped, waited for it to cool a bit and added oil, only to use the washers 5 miles later and then the windscreen washer light came on (this also comes on when the bottle is not far under half full) :(
 

LostKiwi

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Absolutely fine to mix different brands. I would not mix viscosity though and would ensure its all the same base type (semi-synth or synth for example).
 
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d215yq

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Absolutely fine to mix different brands. I would not mix viscosity though and would ensure its all the same base type (semi-synth or synth for example).

Thanks, with that consumption is there a need to change viscosity? The one I bought was cheapest 10W40 to MB 229.3 (IIRC) semi synth and I'll use the same buying criteria this time if I don't go for a thicker one
 

LostKiwi

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I wouldn't bother. 500ml per 3000 miles is fine. I'd worry if it were more like 1000ml per 1000 miles.

Just top up the oil before each long trip so as not to get the light on (you should check it anyway in case the bulb blows!)
 
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d215yq

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I wouldn't bother. 500ml per 3000 miles is fine. I'd worry if it were more like 1000ml per 1000 miles.

Just top up the oil before each long trip so as not to get the light on (you should check it anyway in case the bulb blows!)

Thanks, I do check every month but it is so sensitive to camber even the slight camber of the streets where I park will make it seem either full or empty (depending on which way it's parked) so can only really check to see if there is oil present rather than exact level. I just put in 300ml every time the light comes on to maintain a good 1/2 to 3/4 level. I think I'll keep with the 10W40, it's not too onerous to keep topped up...
 

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In winter when one does less long trips, the oil gets quite contaminated with fuel and condensation and gives the appearance of not using any oil. However, if you were to give it a longish blast down the freeway, presuming your thermostat is working properly, that contamination will evaporate out and the oil level will go down very quickly. In summer, engines get to operating temp more quickly and burn off the contaminants more readily.
Ian.
 
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d215yq

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In winter when one does less long trips, the oil gets quite contaminated with fuel and condensation and gives the appearance of not using any oil. However, if you were to give it a longish blast down the freeway, presuming your thermostat is working properly, that contamination will evaporate out and the oil level will go down very quickly. In summer, engines get to operating temp more quickly and burn off the contaminants more readily.
Ian.

Thanks, though even in winter most of my journeys are 100km+, and minimum is 30km. I cycle/walk for anything less.. Car seems to get to operating temp (as oil pressure drops from "3" when cold to "2" on idle) after about 5-10km. It just seems to use more in summer, maybe as the operating temperature is higher; after a mountain climb in v hot weather oil pressure at idle can be 1.5 and temp gauge can read 105 instead of normal "2" bar and 98 degrees it does in all other scenarios. It doesn't seem to cause problems though or lose coolant, just gets through a bit more oil.
 

oigle

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Given your location and temperature ranges, perhaps the oil viscosity you are using may be a little on the thin side for summer. The fully syn oils claim to cover a wide range of temps but I know Spain can be very hot (like Oz). Perhaps you might consider a higher viscosity oil? As you said most of your trips are quite lengthy, a thinner oil when cold is of little benefit to you. I don't know if you do extended mileages on your oil or change regularly, but if you change yearly, I'd consider a non-syn 15W/40 like Shell Rimula for your type of driving. I use that when towing my van in Oz temps and use some, but little, oil between changes. Much cheaper oil too :)

Ian.
 
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d215yq

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Given your location and temperature ranges, perhaps the oil viscosity you are using may be a little on the thin side for summer. The fully syn oils claim to cover a wide range of temps but I know Spain can be very hot (like Oz). Perhaps you might consider a higher viscosity oil? As you said most of your trips are quite lengthy, a thinner oil when cold is of little benefit to you. I don't know if you do extended mileages on your oil or change regularly, but if you change yearly, I'd consider a non-syn 15W/40 like Shell Rimula for your type of driving. I use that when towing my van in Oz temps and use some, but little, oil between changes. Much cheaper oil too :)

Ian.

Thanks for the recommendation. I've moved within Spain and it's now 30-35 degrees in summer instead of 25-30 where I used to live, I also wish I had working A/c for the first time! I'll see if that oil's available. We get sub 10 degrees temps about a month a year although I do go skiing a few times where it could be -5 but that's the exception so shouldnb't be a problem. I intend to change every 15k miles/8 months but depends how busy I am, it's at 10 months now and as it's forecast to be the coldest weekend on record I think it might have to wait a little longer :)
 


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