i have a 1985 6.9 turbo idi,temps outside been getting in the 30s at night, will get alot colder in a few months,what weight oil should i use,thanks

 

15w40 is fine unless you're getting into truly frigid temps, though I use 5w40 synthetic year round. I started using it in winter so it would build oil pressure faster, and also to keep from cooking oil in the turbo.

 

i have some 5w40 i was going to put in,i just didnt no if it was to thin,i didnt want to hurt the engine,

 

I've been running 5w40 synthetic in mine for maybe 3 years and 35k miles. Particularly at single digits or below zero it cranks over much faster and gets oil pressure far sooner than when I used 15w40. "Thinner", that is flowing easier, during cold starts is a good thing. It's still 40wt at operating temp.

 

i stick with 15-40 valvoline all fleet year round. i just let the engine warm up for a few minutes before taking off. 495,000 miles on it so far without any issues.

 

15W40 is fine, according to the owners manual. If you already have weeping seals, 5w40 will make them leak badly, because it is thinner.
Otherwise, it's fine as well... but remember to change your oil on a regular basis; just because it's synthetic, doesn't mean that your engine produces any less soot.

In my opinion, once the temps get around 20F or below, try to plug it in at night. You might even put it on a timer, so the block heater is only on for, say, 4 hours before going to work if power is very expensive.

A block-heater-warmed truck will fire up nicer than one that isn't, and it should be less hard on the engine in any case.

 

I run 15-40 year round and it works well enough. Having said I would love to put 5-40 or even 0-40 in it for winter but the old beast uses enough oil as it is I can't justify the added cost.

I had a Golf with the 1.9 turbo diesel and I put 0-40 in it over the winter, it made a big difference on how fast the engine cranked when cold and started.

 

I use 15-40 year around here in northern Nevada, and it can get down in the teens.


It`s great to use a block heater to warm the coolant, but what about the sludge in the pan? That cold oil doesn`t pump as fast when it is cold, and it is important to get the oil to the vital parts as soon as possible.


I use the block heater as well and a oil pan heater.




Charlie

 

For reference at some point oil is genuinely just too thick to work. I had 20w50 in my 460 truck and had to use it one bitterly cold morning I'd guess about zero degrees, maybe negative single digits... I failed to start the IDI on the one shot I got stone cold (old batteries, crappy cables, etc. since fixed), either glowed too long and didn't have enough to crank or I blew it on amount of fuel on the two revolutions it would turn when that cold.

Either way, I fired up my 460 truck. It had been sitting at least 6 months, but dutifully cranked over and lit off... To a clatter of valvetrain noise that didn't go away after a couple seconds. Eventually it went away and I saw pressure on the oil gauge jump to 10 or 20 psi and slowly climb to 40 and stay there. This engine normally pegs on the relief valve when cold in any temps and running thinner oil. I was worried about snapping the hardened oil pump driveshaft. I let it idle a long time before oil came up to 75-80 psi on the relief and didn't drive it until it dropped. I ran the engine every couple hours to keep some temperature in it, and changed the oil that night to 5w40 (outside, in single digit temps!), no more problems with oil pressure.

So there are concerns with thick oil in very low temperatures. With an IDI the oil pump is gear driven so no worries about snapping the drive, but lack of lubrication on cold starts can be a problem.

 

I've been running 15-40 synthetic in my truck since owning it, about 3 years. Wouldn't dare start it below freezing without having a block heater, oil pan heater and battery heaters though...

 

I've always ran 10W30 Diesel oil in winter, and 15W40 summer. Very noticeable difference in cranking speed and oil pressure during cold starts on 10W30 vs. 15W40 for winter use. No difference in oil consumption at all either.

Although i've heard lots of good things about the synthetic 5W40 witch I plan on trying out this winter!