It has been in the 20's here recently. Thw w123 300d is about 800 miles from it next oil change to the 'winter' oil (Rotella T6 5w40). Am I hurting the car by starting it with 15w40 dino oil?

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Ben
1987 190d 2.5Turbo

I wouldn't think so. Check your owner's manual, though, for different viscosities for different temperature ranges.

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14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

I've always run 15w40, while ohio isn't the coldest its not the mildest either. Never had starting trouble.

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68 280SL - 70 280SL - 70 300SEL 3.5 - 72 350SL - 72 280SEL 4.5 - 72 220 - 72 220D - 73 450SL - 84 230GE - 87 200TD - 90 190E 2.0 - 03 G500

Nissan GTR - Nissan Skyline GTS25T - Toyota GTFour - Rover Mini - Toyota Land Cruiser HJ60 - Cadillac Eldorado - BMW E30 - BMW 135i

I run 15/40 year round. 25 degrees F today and it has worked fine in - and single digets.

you will notice it cranks over faster with syn oil when cold. But with a healthy glow system and good warm up time will be fine running the dino

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________________________________
1980 300CD - 130,000 Daily Driver
1984 300CD - 325,000 Dad's summer cruiser

1977 K10 - The Grinch - lifted, locked, winch, 37's. Beadlocks.. 379 t Detroit Diesel
1956 Willys Wagon - buick 225 oddfire v6
1982 SJ 410

You are not hurting it unless the thicker oil is resulting in you having to crank over a lot longer. Does not sound like that is the case. If you have a block heater, it wouldn't hurt to plug it in.

If it gets below 15 F, you will likely feel more of a difference in how the motor turns over.

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

I've always ran 15w40 year round in my Benz's. Never noticed it effect starting, even when it's 15 degrees outside.

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1981 300TD 4 speed manual
Euro bumpers, zender valance and skirts, H&R springs, billy HD's, leveled sls, real AMG Pentas 16x8 et11, vdo boost/egt gauges intergrated into ash tray, eurolights, led 3rd brake light

a 40 weight oil is a 40 weight oil, there is such an old misconception with the "W", which stands for an oils "winter grade", NOT having anything to do with it's weight......a 15w multigrade oil performs as a 15-weight oil at 32 degress fahrenheit, a 5w oil performs as a 5 weight oil at 32 degrees, at hot temperature BOTH perform as a 40 weight oil.....thats how it works....i'm sure i'm opening a huge debate now, but those are the facts, i know about lubrication and i'm sorry but i cant stand to see people go 'round and 'round with the same old misconceptions and stereotypes

i use 100% synthetic oils and fluids in all my vehicles and other equipment......the best deserves only the best !

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-Justin

I believe in extreme automotive perfection whenever possible.......there is no such thing as "It doesn't matter" !!!

1985 300 CDT - 287k miles

1980 240 D - 340k miles

With extras !!

http://facebook.com/BenzDieselTuner

http://facebook.com/SWFLAlternativeFuelsClub

http://facebook.com/SWFLBenzClub

http://SWFLBenzClub.com

15w40 was probably the type of dino oil your 123 was originally designed for.

I remember running a 115 (1976 300D) in Chicago in the early 90s and most drivers did not use synthetic oil including me. I could start the vehicle down to about 0F.

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-- Chris

'95 E300, 216k miles, Silver Surfer
'05 E320 CDI, 138k miles
'07 S550 4matic, 69k miles

Gone but not forgotten:

'76 300D, 350k miles?, SOLD in 1995
'75 240D, 300k miles, SOLD in 1991

speaking of "back in the day" , my father, who is a Mercedes mechanic by trade and had his own shop in Florida for many years, back in the days these cars were all new, his "shop oil" was always 40wt Castrol GTX, by the 55-gallon drum, whatever came in got it and it was never a problem.....

__________________
-Justin

I believe in extreme automotive perfection whenever possible.......there is no such thing as "It doesn't matter" !!!

1985 300 CDT - 287k miles

1980 240 D - 340k miles

With extras !!

http://facebook.com/BenzDieselTuner

http://facebook.com/SWFLAlternativeFuelsClub

http://facebook.com/SWFLBenzClub

http://SWFLBenzClub.com

All I run in all my diesels is Rotella 15/40 diesel oil.
Period.