skratch77

My car has been done for a few days but I'm waiting for temps to warm up before starting it.

I'm running 5w40 8100 and it' been 1-7 degrees for the past few days.

today we have a high of 7 lol

JimGnitecki

Well you don't say whether you mean degrees F or degrees C, which makes a big difference. But it also sounds like you may have just finished doing internal engine work on it? If so, and if this is indeed the very first engine startup since internal engine work was done, I'd either wait, or if you have an engine block heater installed, at least have had the block heater on for several hours before doing so.

As we all know (don't we?), starting up an unheated engine at very cold temperatures is what causes a disproportionate amount of wear each time you do it, as the engine oil is too cold to circulate and lubricate properly. This would be particularly bad with a newly reassembled engine.

I grew up in Winnipeg, Manitoba, Canada, where you HAD to plug in your engine block heater every time you parked the car for more than a couple of hours in cold winter weather. If you did not, you could actually HEAR the squeaking of metal on metal for a couple of seconds. In that city, at least at that time, most public parking lots like hotels had electrical receptacles to plug your car in overnight! No kidding.

I remember how unhappy My Dad was when we came out of a winter holiday party at about midnight and he had to start the family car which had been parked in the street (no receptacle). The engine cranked VERY slowly and the squeaking would make any machinery-aware enthusiast cringe.

Jim G

skratch77

No internal engine work,but I did have the top end done for valves and adjusters last year.

just did a differential swap but it' been sitting in really cold temps for about 4 days.

oh and yes Fahrenheit temps so about -16-20 celcius

JimGnitecki

Given the new info, I'd say starting your car should be fine, BUT if low temperatures like this are normal in your area, and the car is a daily driver started frequently in cold weather, you really should be running an engine block heater. The cost of both the heater and the ongoing power use are both pretty low compared to the cumulative damage done with frequent unheated cold weather starts.

Jim G

hachiroku

5W oil is good til -30 F per charts online which equates to -34.4444 Celcius

Solo wing

http://bevo.mercedes-benz.com/bevolisten/224.1_en.html

skratch77

Guys I know the oil is good but our cars have horrible bleed down on the top end and the first 20-30 seconds will likely be very little oil to lubricate it.

I will post a video of my car in warm weather with 0w40 on how bad its stats were before doing the top end over under warranty

I just don' want to harm the top end after what I've gone through with it.

I am Jeff

The bleed down is most prominent in hot weather and shutting off the engine while it' still very hot. In that scenario, the 0 weight oil would be too thin and that' when the bleed down occurs. That isn't your issue in your situation, the 5 weight oil will be thick enough to not bleed past the lifters.

hachiroku

A good oil with a GOOD additive package should protect you. Thinner oils will travel faster...you should have concern IF running a thick oil which can take easily half a second to fully flow through the engine. Ambient temps do also affect certain oils in terms of flow due to thickening of the fluid. Synthetics are not as effected by temps but some are.

skratch77

Just got it back and yes I watched those videos and was concerned about the 8100 because it came in last or almost last place in some videos

hachiroku

those tests are not entirely a controlled test due to the fact they aren't testing base viscosity/weight of the oil at room temperature. some brands of synthetic oil like 5w pour, flow, and protect like a 0w oil. Eneos is a good example of that. Dyno's show the 5w makes more power than other 5w's because Eneos 5w is pretty much a 0w oil. Thinner oils will generally produce more HP, but not always. drop down to a 0 weight oil, is my recommendation...and if you're not using LiquiMoly MoS2 additive, do so as it'll coat your internals with good good stuff.

NotABaller

So 0w40 is unarguably the best during cold temps. Given that, how bad is it to cold start with nearly 0c oil temps?

hachiroku

0w oil is the thinnest weighted oil available. 0w also has the thinnest viscosity in cold temps to aid flow during cold start ups.

SteveE400

Let me put it this way -- the cars are designed for it! I live near Chicago, so weather maybe even a bit colder than Toronto. My garage is unheated and un-insulated, so temp is whatever the ambient air temp may be. The only time I needed any kind of heater was back several decades when it hit -26F overnight, and at a time when synthetic oils didn't yet exist. Other than that, all my cars start fine and last just fine. I typically keep them to 150-200K miles, and have never had any internal engine work needed for any of them. You just need to drive them gently at first start, until they reach normal operating temperature.