Which oil do you think is the best among these two.

Not even remotely close to old, worn out perhaps depending on how its been treated, but not old by a long shot. "Older engine" to me usually indicates pre-emissions. That is a tier 4 epa emissions engine, so pretty much brand new in terms of the requirements

 

If you got a new engine with no oil consumption stay with the 5w-40. It will flow better during the initial warm up leading to less wear. 15w-40 seems to be made for the vehicles already leaking or burning oil which honestly if it’s doing that you should stick to t5 as it’s cheaper and you’ll be adding more often anyhow. Only issue with that is you need to change the oil more often.

 

https://knowhow.napaonline.com/understanding-oil-weight-numbers-bottle-mean/

Oil is a pretty technical subject. Ambient temperature carries a lot of importance on what weight of oil to use. If you're running in summer, with high ambient temperatures you'd typically select something like a 15W-40. If its winter and you're seeing temperatures around freezing then something like a 5W-40 would make more sense.

I used to work way up in the north. We'd see a temperature range of -35°C (-31°F) to +35°C (95°F) through out a calendar year. Summer we'd usually put 15W-40 and winter would be 0W-40. Although one dealer I was at only ever had 0W-40 in the bulk reel year round. 0W-40 typically costs more than 15W-40 but it has pretty much the same upper ambient temperature range. Its big advantage was you had excellent flow in the cold.

At the end of the day, there's no cut and dry answer. Best to defer to the owner's manual and use their recommended oil grade for the conditions you're operating in.

 

But that has nothing to do with it being "for" older engines. Some brand new engines come out of the factory with T6. It's for all diesel engines if you want to run a full synthetic.

 

when in doubt, check with your company shop, or your garage that services your truck.

or check the owners manual for that particular engine.

brand names may not always be as important as viscosity, pricing, availability.

over the years, the company shops would tell me either Delvac, Shell, Mobil, etc.

if they are brand specific, then go by what they say.

 

I run 15w40 year round non synthetic

 

Why don’t you search for a local oil distributor in your area. See what they have to offer. I use one here locally and they have there own “Houseblend” which exceeds all the name brands at 1/2 the price. It’s a synthetic blend 15/40. That’s all I’ve been using for the last 6 years since I found them.

 

You'd have to compare the ASTM technical specs to see the actual differences. I have used the 5W version several times but local farm store has the 15W version now too so I might give it a try since it is due pretty soon and see if I actually notice any difference. It's been around for several years now but only somewhat recently started seeing it on store shelves. Not as common as the original 5W version.

 

Good compare between Rotella and Delo. Great channel