I recently dicussed engine oils and their viscosity with a local mechanic.
He has this theory that aluminum block engines should always be serviced a grade lower in viscosity then cast iron no matter what the ambient temperatures. I live in Hawaii and ambient temperatures never go below 0 degrees Celcius, so I have always been using Penzoil 20W-50 for my cars. ( 85 190E 2.3, 88 300E, 92 400E).This guy suggested I use 10W-40 instead for the aluminum block. He claims that with the higher viscosity of the 20W-50 there'll be no oil around the rings to protect the cylinder walls from being shaved by them at start up, resulting in compression loss and ultimately 0 compression on the cylinders.
Any thoughts on that? What about synthetic oils?
Thanx,
F.J.

It seems to be a general consensus that synthetics are very good in MB cars. I don't use them in my 81 sd because of the added cost and the fact that the Sd uses 7.9 quarts per change . I change every 2500 or there abouts as we live on a gravel road with lots of dust. I also change the air filter more often , I use Delo 400 15/40. and never have to add between changes...
William Rogers.....

William,

Use multivis called for by your manual.

Mechanic opinions are interesting, but likely without merit.

Always use synthetic - it is better in every respect.

George

Brother of The Benz, stephanson
There is always the topic what type, grade, manufacturer(refiner) maybe even color with the rebirth of the Purple Royal Triton.
More likely most of we Benz owners settle on 15/50w as an all season weight where you don't have the sub cold temperatures then 5/30w.
Be it Dino or synthetic type.
The Petroleum Companies truely must love the Benz owner for we throw away more good oil than all other cars owners because of our oil change frequencies.
Others cars owners can not come close to the high engine mileage life that we can boost of.
Me, I use Mobil I 15/50w and change it and filter every 3500 miles.
My 103983 engine turned 179,000 miles yesterday returning from a trip to New Mexico and back to Houston.
My engine has yet to be opened; not even valve stem seals and there are no leaks and oil consumption at 1 quart/1700 miles.
I know there are those who think that is high consumption but I'll live with it.
So you will recieve many opinions on oil, sift through them and make your choice.
Oil is cheap, either dino or synth compared to the alternative, engine rebuild.
Happy Trails Beep Bep from The Spiderman in Houston!!!

Your use of 20-50 weight dino oils if within parameters of your owners manual is ok. Synthetics, on the other hand, have more stable viscosity at higher engine operating temperatures. Therefore, a quality synthetic 40W at high engine temps provides better lubrication than a dino 50W. See the redline web site for a good discussion of synthetic vs dino oil. http://www.redlineoil.com/products.htm
A partial discussion follows:

VISCOSITY GRADE SELECTION
The proper viscosity grade to use depends on many factors such as ambient temperature, miles on the engine, bearing and piston clearances, and type of service. A general rule of lubrication is to use the lowest viscosity possible which will provide the proper separation of metal. Anything more than this minimum will increase power loss due to friction and will reduce the pumpability of the oil at all temperatures. However, one must consider synthetics differently when determining viscosity requirements. At high speeds, a petroleum 5W30 can appear to be a 10W in the bearings due to the shear stress, yet Red Line 5W30 will actually be an SAE 30 in the bearings. There is a significant difference in lubricating an engine with a 30 compared to a 10W. Red Line Synthetic oil will provide better viscosity protection than the next higher petroleum viscosity grade. If clearances are tight and very little lugging occurs, then the 5W30 or 10W30 should be adequate. Less turbo lag will be noticed with the 5W30. If ambient temperatures will regularly climb above 100°F, then the 10W40 would provide an additional safety margin. If the engine is air-cooled, or if the engine is older and has greater bearing and ring clearances, the 15W50 and 20W50 will develop a thicker oil film. If very low temperatures occur, the lower viscosity grades, (5W30, 10W30, or 10W40) will flow better and lubricate the engine more quickly after start-up.

BOL, Roger

__________________
Roger
1983 300CD 246k sold
1998 C230 52k
1980 450SL 75k needs AC
1999 Subaru Outback Ltd 43k

Thanks a lot guys. Quite a bit of valuable advice.
I'll look up the mentioned links.
I am now strongly considering switching to a synthetic oil in my M119 400E.
Are there any particular considerations to be taken into account when switching over from regular to synthetic?
Thanks again.

F.J.

Brother of The Benz, rbauman
Considering the performance of "RedLine" synthetic motor oils, I definently would use theirs if it was as available as Mobil I.
So I use the Flying Red Horsey Oil.
Happy Trails Beep Beep from The Spiderman in Houston!!!

You don't mention how many miles are on your engine. If your engine is "seeping" any oil, it may become a leak when you switch to synthetic. Not that it definetly will, but it is known to happen. Also, synthetic oil likes like a cleaner in your engine. If your engine is gummed up in any way, synthetic wil loosen it up and possibly plug up the works inside. You could first switch to semi-synthetic, to "ease" the engine into full synthetic oil.

__________________
1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member

LOL!! That made me laugh. Hey Donald, do you know how to make the "Flying Red Horsey" light up?

__________________
2006 E350 w/ 155k miles (Daily Driver)

Previous:
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)

Brother of The Benz, david
No I don't know how to light my Red Horsey?
We users of synth oil always caution those with engines in the mid to high miles to expect some oil seepage and possibly oil burning for a short period of time; resulting from the detergent action of this type of oil.
I converted when my 103983 engine had mid miles as I remember with out getting the older log book out and I never experienced this.
I was always of the opinion after studying the crankcase ventilation method; that the crankcase was at minus atmospheric and at that pressure would retard any seeping beyond the normal wet line interface.
Possibly there are others who can add to this?
Happy Trails Beep Beep from The Spiderman in Houston!!!

Donald,
You have to wave your Speedpass (TM) in front of it to make it light up!

I switched to 1/2 synthetic at 90k miles, and ful synthetic at 95k miles. Absolutely no leaks, and engine is burning NO oil! This is on M104 motor in 95 C280.

__________________
2006 E350 w/ 155k miles (Daily Driver)

Previous:
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)