Is 15W-40 too thick for below-freezing temps?
 

Over here it doesn't get very cold, but last night was a bit colder than usual, about 12F and I parked my 82 300D outside overnight. This morning it took me almost 10 minutes of repeated 30-second glow cycles to get it to start. It was probably 20F at the time. I've done all my fuel system and glow plug maintenance as well as valve adjustment and the car usually starts perfect when it's not too much below freezing. Currently I'm on 15W-40 Delvac 1300 and I'm wondering if anyone in this situation has seen a significant improvement after switching from 15W-40 to a lighter oil or if something else is causing the difficult starting.

Yes, 15W 50 is probably too thick for 12F starts!

Use 10E30 until the weather warms up, then switch back.

Peter

At these temperatures you should use Mobil 1 0W40. This oil, as well as the Mobil 1 15W50 are the only Mobil 1 Oils approved by Mercedes.

go with delvac one. 5w40

I would aviod sunoco sythetic 5w 40 as it is not all that free flowing at cold temp.

Auto zone sells 0w40

Or use your oil and use your block heater.

Dont throw away 40 dollars worth of oil if this is not a common problem.

Plug it it for about 1 hour and you should be able to start it.


IF you are going to use regular oil 10w 40 would be better (dino)


But overall delvac one is the best stuff you can buy.

When you fing a place that sells it buy alot of it.

I run that in the winter and mobil 1 15w 50 in the summer.

have fun

bob c

mine starts down to about 12deg F without the block heater.
usually wait 30 seconds before cranking after turning on the glow plugs.
15/40 year round

below 12 deg F i use the block heater and it starts on 1st crank.

Howdy,

I used 5w40 mobil 1 delvac on my last change and have had no probs starting my 190d 2.2 down to 8 deg f on 1 or 2 glows.

Sholin

I use Delo 400 which is a 15W-40 oil. I started my 300D today for the first time since before Christmas and it was at 10 degrees F. It started fine after one glow plug cycle and idled great. Unfortunately it's still covered with about 3'-0 of snow!

Would it be a good idea to mix Mobil 1 15w-50 and 0w-40? Since mine leaks quite a lot, could I d this mix by using 0w-40 as a "top-off"?

Well you aren't "supposed" to mix any oils, but I doubt they'll mix and eat through the oil pan or something. ;) It should be alright.

I use 15w50 <edit, thanks 82-300td> Mobil1 year round, I'll start using the block heater once it is in the low teans when I start it up. I thought it was funny if you look at the back of any Mobil1 container (whether 5w30 or 15w50) they list the same pour point, -44*F I believe.

BoostnBenz, I think Mobil 1 is 15w-50 not 40 :D . I use it as well but I don't see why they would not mix.

In the last two days it's been in the low-mid 20's here, usualy in this it starts well in this but this time I had to glow for two 30-second sets and crank for about 20 seconds before 2 or 3 cylinders caught at half throttle. The other cylingers caught on after about 30 seconds. After that, it runs like a real gem. I thought adding some 0w-40 might help this.

I normally prefer to glow more and crank less. It seems like after about 10 cranks (each cylinder twice) there is enough fuel in there that when it does catch it runs like crap as it spews that fuel out. I would imagine that at this point it would be much harder for the starter to start it anyway. Have you checked the resistance on your glow plugs? (.6-1ohm)

#1 is 0.07 ohm, #2-5 are 0.94ohm.

Have you checked your compression then? I can't imagine adding 0w40 adding much benefit as it is already synthetic.

Do you know your webpage is some site in germany about compact cars?

3-325
4-370
5-330
#1/2 I don't know, my cheapo tester broke and autotestsystems.com said I never bought on from them after i returned it with a copy of the packing slip!

As for my homepage, I happen to like small German cars. "In November 2003, the smart brand was introduced to the American public at one of the world’s most popular marathons, the ING New York City Marathon. smart gmbh plans to enter the American market in 2006." I plan to buy a CDI model if they offer one. I will still keep my TD until it dies :D

Well, -44F is about as low as you can get in the typical oil testing lab (diesel fuel usually doesn't have a pour point less than about -30), and "pour point" is the temp at which it will visibly move in the test aparatus in either 5 or 10 sec if I remember correctly. Long time since I did any of that stuff. Usually tested by chilling the oil or fuel in a brass tube submerged in an acetone/dry ice mix.

The lower number is the cold viscocity, the higher number is the hot viscocity rating. May and may not be all that different for a 15W and 0W synthetic, since they don't change viscosity all that much anyway.

The visible difference I've seen is that the 0W oils pour almost like water at room temp, while the 15W-50 pours more like oil. I'd assume they have similar characteristics at very low temps as well, with the 0W-40 being "thinner".

Peter