That is what I run in mine. The 15w40 is for diesels. I used to run it in my gassers too but I don't anymore. It will cause some problems in some gassers.

Tom W

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

I run 15W50 or 20W50 in my gas vehicles.

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I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

Such as...?

I stopped using 15-40 as well since the detergents work too well, clearing the false seals around my timing cover and causing leaks, and also because it is too heavy and makes the car vibrate (or rather, the overburdened oil pump does that).

My current rule of thumb is: With engine hot (at operating temperature) and when stopped while in gear: If oil pressure is above 1.0, then the oil is too heavy.

I have been using 10-40, and if the weather was colder I'd use 10-30.

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2008 E350 4matic / Black/Anthracite

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Gone but not Forgotten:
2001 E430 4matic, 206,xxx miles, Black/Charcoal
1995 E320, 252,xxx miles, Black/Grey
1989 260E, 223,00 miles, Black/Black

I put the 15w40 rotella in my 84 500sec when I first got it and found that a hydraulic lash adjuster would stick and make the valve tap. When the car was good and hot it would stop tapping and after running the oil 1500 miles it would stop as well. I switched to 10w30 mobil one and the tapping stopped. I ran that one oil change and switched back to my beloved rotella and the tapping came right back. So next oil change I went back to the mobil 1 and stuck with that.

I think maybe there might be other things too but that is my experience.

Now I understand that oil is designed for different applications and engines are designed for different oils and you should use what is called for whenever possible.

Tom W

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.