Synthetic Oil - Do you use it in Cummins Engine?

[Kidoo]

Anyone did switched to synthetic oil? I wonder if there is any bad effect to switching to synthetic oil on a 2003 Cummins. My engine book says we can do it.

I would like to put 10W40 year long. It should be easier to start in colder temps and should last a year per oil change.

Anyone using 5w40 synth. year long? This is what I use in my Ford Diesel.

[Blaster_Man]

To answer the OP's question, no, can't see the advantage. If you have engine preheat, the dino starts fine in cold weather.

[tinkerer]

Being we have a lot of farm equipment with diesel engines (some have Cummins) we buy oil in bulk and have went all to 5w-40 full synthetic. With oil sampling we have went to 500 hour oil changes and have yet to get back a bad sample. I use the same oil in my C7 Cat but change it once a year which is about 7000-8000 miles. I will be taking a sample this year. In my opinion one of the biggest advantage of synthetic oil is that at start up the engine get lubricated quicker. I have not noticed any notable increase in fuel economy. They say it is about 2% which would be very difficult to detect.:)

[noteven]

If you look at the specifications 5-40 full synthetics actually have better high temp viscosity performance than many 15-40's plus offer the flowability for cold starts.

15-40 is not for my engines: Cold lube oil and ATF

Also full synthetics will not coke in turbocharger bearings if the engine is stalled or shut down at high exhaust temperatures before the turbo materials are allowed to cool out.

Like "low fat" advertising, there is apparently a bit of fudging in what you can label as "synthetic" oil.

[Passin_Thru]

You can run 15W-40 all year if you use an engine preheater. Done it for years. Can't quite find the $ for using syn. Not worth the big bucks unless you are running 130,000 miles a year. New syn Amsoil can run 15K or more. I go by oil samples, not by the mfg.

[gswcgi]

I have a 2003 Cummins 5.9 engine with 150,000 miles on it and change the oil every 7,000 miles (including all of the filters).I use dino oil only and it still doesn't burn a drop of oil between oil changes. I have had two other Cummins diesels in a commercial fishing boat that had 5,500 hours on them when I sold it, only used dino oil in them as well. Neither burned a drop of oil.I have a CAT engine in my DP RV now and only use dino oil. Both CAT and Cummins will tell you that they don't recommend synthetic or not recommend it and they both will say that synthetic does not change the oil change intervals. If you want to use synthetic go for it!

[ScottG]

Kidoo wrote:
The 10w40 synthetic rotella T6 here cost 104.00$ for 5 gallons, the 15W40 Diesel cost 83$. For the difference I would go for synthetic.

But I never tried this engine in very cold weather with 15w40, I know my Ford needs the 0W40 to be sure it will start in the minus 30 temp.

Me too and I can go a year or more between 5000 mile changes so that's really not that much more money in the long run.

[Sully2]

Do it....wont hurt a thing

[Kidoo]

The 10w40 synthetic rotella T6 here cost 104.00$ for 5 gallons, the 15W40 Diesel cost 83$. For the difference I would go for synthetic.

But I never tried this engine in very cold weather with 15w40, I know my Ford needs the 0W40 to be sure it will start in the minus 30 temp.

[Fishinghat]

ScottG wrote:
Your eng should start easily down to -40 with grid heaters - about -30 without them so syn oil isn't really needed.
You also have an eng that will go 700,000 to well over 1 million miles with normal maint. So it isn't really needed for longevity either.
I tried in in two Cummins I owned but neither one got any better mileage or showed any kind of change.
But if your the type that just likes to use the very best to take care of his toys (and I sure repect that!) then go for it. It sure wont hurt.

X2 (Couldn't have said it any better.)

[ScottG]

Your eng should start easily down to -40 with grid heaters - about -30 without them so syn oil isn't really needed.
You also have an eng that will go 700,000 to well over 1 million miles with normal maint. So it isn't really needed for longevity either.
I tried in in two Cummins I owned but neither one got any better mileage or showed any kind of change.
But if your the type that just likes to use the very best to take care of his toys (and I sure repect that!) then go for it. It sure wont hurt.