Ive always used Rotella 15-40 through out the year here in Houston ,have now come across some harder starting issues once 40 or below temps come into the area.Ive have done all the necesary upkeep on the glow plug system but have never thought about oil viscosity as being the issue.

I would keep that in your car and just leave the glow plugs connected for 45 seconds... just leave the key there... no restarts... time it... this is recommendation from the FSM..

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1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/diesel-discussion/10414-help-i-need-check-stretch.html

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html

If you've been using the same viscosity oil for multiple years and are only now having a problem, I'd look at something else. Old battery? When's the last time you adjusted your valves?

I run 5w-40 during the winter, temps in the teens.

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617 swapped Toyota Pickup, 22-24 MPG, 50k miles on swap

What car do you have?

I use 15w40 year round, down to about the coldest temps we get here in Tucson (which can be subfreezing, down in to the 20's, overnight) and haven't had any issues starting.

If your glow plugs are indeed pretty fresh, and working well, you might look in to the health of your battery, the condition of the battery cable (can be hard to discern since it's wrapped in insulation, but if it's of unknown age, it would be worth looking at as closely as possible), and the health of your starter. If your engine is not spinning fast enough under cranking, good glow plugs won't be enough.

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1979 300D 040 Black on Black - 1985 300D Maaco job (sadly sprayed over 199 Black Pearl Metallic) on Palamino

http://i.imgur.com/LslW733.jpg

The Baja Arizona Oil Burners Send a message if you'd like to join the fun
Left to Right - UberWasser, Iridium, Stuttgart-->Seattle,, mannys9130

Visit the W123 page on iFixit for over 70 helpful DIY guides!

You might need a starter,I bought my starter,and alternator at Advanced Auto Parts,they work fine.Forget the BS about buying Bosch,and save your hard earned money.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran, deutschland deutschland uber alles uber alles in der welt

Today there is no good reason to use different oil in the summer than in the winter. Todays multi-vis oils cover a wide range of temperatures, and the synthetics such as 0W40, cover even arctic conditions. Of course, a heating device may be needed in true arctic conditions. Your oil should be fine year around in your location. A problem starting is an indication that something else is going on, in my opinion.

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'97 E 300 D

Lubro Moly 5w40 Full Synthetic (what I use year round)

Temps around here range from 7°F in the winter to 110°F in the summer.

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Onus probandi incumbit ei qui dicit, non ei qui negat

I recondition w123/w126/w124/w140/r107/r129/ steering boxes!


1984 300D "Elsa" odo reset 6/2011 147k
1983 300TD "Mitzi" ~268k OM603 powered
1995 E300 "Adelheid" 262k [Sold]

If you are having trouble at that temperature with 15w40 in the crankcase, I would second the remark about your starter and/or the battery, but also ask when the valves were last adjusted.

I use 5w40 Rotella but around here it gets COLD in the winter and 15w40 is fudge in those conditions.

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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

This exactly. I run the 15w-40 synthetic year round. Even when I lived up north, I never changed oil weights during the cold winter months.

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-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250

I run the Shell Rotella T6 5W40 year round.

+1

I also use this oil in my w210 e320 and 2010 Hyundai Genesis 2.0T. My buddy uses it in his Mazdaspeed 3 and Audi A3 2.0T. Very good stuff. Wally World sells it for $22 gallon. Blue jug.

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1987 300 SDL
2000 E320 Wagon

I use 5w40 year round.

-J

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

Delo 400 15w40 all year in both 300SDs. I glow longer when it gets below freezing.

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1991 F250 super-cab 7.3 IDI. (rebuilt by me) Banks Sidewinder turbo, hydroboost brakes, new IP and injectors.
2003 S430 - 107K
1983 300SD - Tanoshii - mostly restored ~400K+.
1983 300SD - Good interior. Engine finally tamed ~250K.
Monark Nozzle Install Video - http://tinyurl.com/ptd2tge

Synthetic. I think 5W40. Going to synthetic makes a difference in the winter so I just switched for all diesels. Valves are adjusted.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

Used rosmella for years but have now switched to NAPA 15-50 Full Synthetic caught the sale in Oct.
Been working Great here in St. Louis, also rebuilt my starter and have the valves adjusted and glow plugs cleaned.

Once it gets warm I will go back to Valvoline Blue, started that this past summer and Alfred loves it, got a sale at Rule King $10.88 gal so bought a case.
greazer2b