20W50 in a diesel

Ball-sack · Jan 21, 2011

Im looking at buying a 99 dodge cummins diesel and the truck is clean, all receipts and such but when I looked at the service records this guy has been using 20w50 instead of 15w40. I asked him and he swears up and down that it's better than 15w40 because he runs it in his wood chipper and it's held up the last 20 years without a overhaul. so I'm thinking either this guy is a frickin moron or maybe he's on tho something here, maybe 20w50 is a better lubricant for diesel fueled engines. What do you guys think?

TreeClimber · Jan 21, 2011

I wouldn't worry about it. The "10" in 10-40 is part of the viscousity. The lower the number, the thinner the oil. An 80-90 is a thick oil, suitable for differentials and other gear'd cases. A 10-30 oil would be used in cold climates, when you need to make sure the oil doesn't 'freeze' (or thicken). The variations between a 15-40 and a 20-50 is minimal. Especially if the rig is a local rig, because our tempatures are so mellow around here. Very little sub-freezing, very little 100+ days. We really do stay in the 40* to 85* pretty much year round.

WA-Wheeler · Jan 21, 2011

Around here 20/50 is fine. I actually run it in my Heep... lots of miles and likes the thick stuff... can be a rough warm up on cold days though. Go with what you want. Its almost all preference.

t1h5ta3 · Jan 21, 2011

most 20-50 oils arnt diesel rated. if the trucks had an easy life and oils been changed frequently , your prob fine.

remember theres alot more to oil than just weight. esp when you get into a turbo diesel... nothing like cokeing some petrol on a shaft that spins 25k+rpm and gets heat soaked at 1600+deg...

look inside the valve cover with a flashlight thru the fill cap. if you see any sludge / varnish / scale etc walk away. it only gets a couple hundred deg in there and if theres any of that, imagine what it looks like in the bearings and in the turbo.

id also use that as an indication of the quality of any mod's he's done to the rest of the truck...

Glenn · Jan 22, 2011

Since when is a woodchipper motor the same as a CTD?

skinny_pedal · Jan 22, 2011

Glenn said:
Since when is a woodchipper motor the same as a CTD?

There both diesel

Ball-sack · Jan 29, 2011

t1h5ta3 said:
most 20-50 oils arnt diesel rated. if the trucks had an easy life and oils been changed frequently , your prob fine.

remember theres alot more to oil than just weight. esp when you get into a turbo diesel... nothing like cokeing some petrol on a shaft that spins 25k+rpm and gets heat soaked at 1600+deg...

look inside the valve cover with a flashlight thru the fill cap. if you see any sludge / varnish / scale etc walk away. it only gets a couple hundred deg in there and if theres any of that, imagine what it looks like in the bearings and in the turbo.

id also use that as an indication of the quality of any mod's he's done to the rest of the truck...

Thanks **** eater :awesomework:

t1h5ta3 · Jan 30, 2011

LOL... the same people that think oil is oil... are usualy the same ones that think beer is beer...

jeffroktm · Jan 30, 2011

ive got an 03 ctd. ive been running 20w50 since the truck was new 200,000 miles and it runs like new. mobile one synthetic. The only thing you are going to notice is when its cold takes a little longer to warm up.