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Oil pressure and Mobil 1 oils

Thunderace

Spa-Francorchamps
Joined
25 Aug 2020
Messages
337
Just had my car serviced and prior to the service they offered me MILLERS 7726CA XF PREMIUM 5W 50, because my car (at 100k+) burns no (read not enough to warrant refilling) oil between services (about 8000 miles) I said that I would stay with Mobil 1.

Yesterday I went out for a long drive and I noticed that the oil pressure was 1 bar higher, usually I consider the car warm when the revs match the bar pressure ( 3000 revs = 3 bar etc.) but now 3000 revs = 4 bar so I thought to myself, they put the Millers in anyway and just didn't tell me!

This turns out not to be the case however, the Indy did use Mobil 1, the difference is that I have always had 0w 40 (Porsche recommendation A40 spec) and they had put in 5w 50, I wonder why they used 5w 50 and whether I should do anything about it?

The point of this post is partly the above but also the huge difference in oil pressures at temperature between 0w 40 and 5w 50.
 
I’ve been using Mobil one 5w50 for a few years now … it’s Porsche approved and I’d defo say stick with it as our cars are now getting on abit … its a tad thicker so oil pressure will show higher and will burn less also (I like you don’t ever need to top up between services)
 
As oil is partially used to help cool the engine, at speed the oil flows greatly effects how much heat is transferred to it. If it is too fast, less heat will be transferred to it. If oil is less dense, the heat transfer will also be less.

if i have my oil science correct (it's a bit rusty) the W40 has a faster flow rate than the W50
film thickness is also important in a hot engine and when your oil starts getting 100 degreeC +, crank journals, etc, greatly appreciate the w50 weight oil.
 
Interesting this oil business, I always thought W meant weight but it doesn't it means Winter, so winter viscocity is to the left of the W and to the right the operating temperature viscocity.

Back to my car the 5 or 0 is pretty irrelevant to me, the 50 to the right may well protect my engine a little better but it will also rob power and economy. My car does not use engine oil as I mentioned earlier so I should have had the 0W-40 oil again as I'd intended.
 
I'd be a bit miffed if it was mine. You specified mobil 1 and every man and his dog with a 996 knows the standard is 0W40, so for them to then go and put thicker stuff in (equivalent to what they were doing in the 1st place) is wrong. The whole point of you requesting the Mobil 1 is all down to viscosity.
 
Hartech recommend Millers 10w 50 ; so that's what I use now...
 
I'd be a bit miffed if it was mine. You specified mobil 1 and every man and his dog with a 996 knows the standard is 0W40, so for them to then go and put thicker stuff in (equivalent to what they were doing in the 1st place) is wrong. The whole point of you requesting the Mobil 1 is all down to viscosity.
Yeah, thanks for that Alex, gave me the confidence that I'm not being ridiculous. I called them and they will replace the oil with Porsche recommended.
 
I used Mobil 1 5w50 X2 in both the 996.2 and 991.1.

It's Porsche A40 spec approved so effectively an OEM replacement option.

At 100 degrees Celsius it has about 18 centistokes viscosity Vs about 9 for the Ow40 option.

Thin oils add about .2 mpg and this is why the manufacturer uses them.

But in old motors 5w50 is basically a free upgrade and does give lovely oil pressure readings on the 996.2, even at hot idle it pulls 2.5 bar.
 
It's Porsche A40 spec approved so effectively an OEM replacement option.

At 100 degrees Celsius it has about 18 centistokes viscosity Vs about 9 for the Ow40 option.

Thin oils add about .2 mpg and this is why the manufacturer uses them.

But in old motors 5w50 is basically a free upgrade and does give lovely oil pressure readings on the 996.2, even at hot idle it pulls 2.5 bar.

5W 50 doesn't show in my A40 list but still, wasn't what I asked for and isn't manufacurer recommended Mobil 1 which was what I expected (and have always received before)

Thin oils affect performance too and .2 mpg is sizeable when you are doing 19.2 mpg, both are decreases in performance.

5W 50 is nothing like "a free upgrade" it was the wrong oil (not the manufacturer recommended) and it offers no benefit, only performance deficits unless an old engine is e.g. burning oil.
 
Is this only for higher mileage engines.? Mines on 37k, so unsure what to feed it.?
 
Actually, Porsche themselves now recommend 5w50 for the 996:

Porsche Classic Oil 5w50

Yes that is generally known but not all 5W-50 oils are made equal and Mobil 1 5W 50 is not a specific recommendation whereas e.g. Millers Oils XF Premium 5w-50 Fully Synthetic Engine Oil is (A40), so when mine starts burning oil I'll maybe move to that.
 
At 37k I would suggest you're still good with the 40 weight oil.

After 70k miles nd 20 winters-worth of cold starts, you might consider a switch to 50. Above 100k then I would say go 50.

However, no engine has blown up because of either viscosity and there is no data other than the anecdotal evidence presented here!

Oil is a marmite thing anyway.
 

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